High tech aids low vision: A review of image processing for the visually impaired
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paper_title: Improvement of reading speed after providing of low vision aids in patients with age‐related macular degeneration

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. ::: ::: ::: Purpose: Age-related macular degeneration (AMD) is the most common cause of severe visual impairment, including loss of reading ability, among elderly persons in developed countries. The aim of the present study was to evaluate reading ability before and after providing of appropriate low vision aids. ::: ::: ::: ::: Methods: Five hundred and thirty patients with different stages of AMD (age 82 ± 8 years) were included in this retrospective study. All patients underwent a standardized ophthalmological examination including evaluation of magnification requirement and careful providing of low vision aids. Before and after the provision of low vision aids, reading speed [words per minute (wpm)] was evaluated using standardized reading texts. ::: ::: ::: ::: Results: For the whole group, the average best-corrected distance visual acuity of the better eye was 0.18 ± 0.15, with 69% of patients having visual acuity of 0.1 (20/200) or better. The mean magnification requirement was 7.4 ± 6.3-fold (range 2–25). Visual rehabilitation was achieved with optical visual aids in 58% of patients, whereas 42% of patients needed electronically closed-circuit TV systems. Mean reading speed was 20 ± 33 wpm before and increased significantly to 72 ± 35 (p < 0.0001) after the provision of low vision aids for the whole group. Between patients with visual acuity < 0.1 and patients with visual acuity of 0.1 or better, there are highly significant differences in reading speed before (0.4 ± 3.8 versus 20 ± 28 wpm, p ≤ 0.0001) and after providing of visual aids (40 ± 13 versus 84 ± 30 wpm, p ≤ 0.0001). Patients with severe visual impairment (visual acuity ≤ 0.1) showed significantly lower improvement of reading speed compared to patients with visual acuity of 0.1 or better following rehabilitation (p ≤ 0.0001). Before providing of low vision aids, only 16% of patients were able to read; in contrast, reading ability was achieved in 94% of patients after the provision of low vision aids for the whole group. ::: ::: ::: ::: Conclusion: Our results indicate the great value of low vision rehabilitation through adequate providing of vision aids for the improvement of reading ability, with a highly significant increase of reading speed without training of eccentric viewing in patients with retained central fixation. The prompt implementation of low vision aids in patients with macular degeneration will help them to maintain and regain their reading ability, which can lead to an increase in independence, communication, mental agility and quality of life.
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paper_title: Principles of modern low vision rehabilitation

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Low vision rehabilitation is a new emerging subspecialty drawing from the traditional fields of ophthalmology, optometry, occupational therapy, and sociology, with an ever-increasing impact on our customary concepts of research, education, and services for the visually impaired patient. A multidisciplinary approach and coordinated effort are necessary to take advantage of new scientific advances and achieve optimal results for the patient. Accordingly, the intent of this paper is to outline the principles and details of a modern low vision rehabilitation service. All rehabilitation attempts must start with a first hand interview (the intake) for assessing functionality and priority tasks for rehabilitation, as well as assessing the patient's all-important cognitive skills. The assessment of residual visual functions follows the intake and offers a unique opportunity to measure, evaluate, and document accurately the extent of functional loss sustained by the patient from disease. An accurate assessment of residual visual functions includes assessment of visual acuity, contrast sensitivity, binocularity, refractive errors, perimetry, oculomotor functions, cortical visual integration, and light characteristics affecting visual functions. Functional vision assessment in low vision rehabilitation measures how well one uses residual visual functions to perform routine tasks, using different items under various conditions, throughout the day. Of the many functional vision skills known, reading skills is an obligatory item for all low vision rehabilitation assessments. Results of assessment guide rehabilitation professionals in developing rehabilitation plans for the individual and recommending appropriate low vision devices. The outcome from assessing residual visual functions is detection of visual functions that can be improved with the use of optical devices. Methods for prescribing devices such as image relocation with prisms to a preferred retinal locus, field displacement to primary gaze position, field expansion, and manipulation of light are practiced today in addition to, or instead of, magnification. Correction of refractive errors, occlusion therapy, enhancement of oculomotor skills, and field restitution are additional methods now available for prescribing devices leading to rehabilitation of visual functions. The outcome from assessing residual functional vision is detection of functional vision that can be improved with the use of vision therapy training. After restoration of optimal residual visual functions is achieved with optical devices, one can follow with training programs for restoration of lost vision-related skills. If an optical dispensary is available where prescribing of low vision devices routinely take place, this will help ensure familiarity and specialization of the dispensary and staff with low vision devices and their special dispensing requirements. The dispensing of low vision devices is an opportunity to introduce the device to the patient, train the patient in the correct use of the device for the task selected, and create a direct and continuous connection with the patient until the next encounter. Following assessment, prescribing, and dispensing of devices, a low vision practitioner, ophthalmologist or optometrist, is responsible for recommending and prescribing vision therapy training to improve residual functional vision. An attempt to present a template for a comprehensive modern low vision rehabilitation practice is made here by summarizing scientific developments in the field and stressing the multidisciplinary involvement required for this kind of practice. It is hoped that this paper and other initiatives from colleagues, the public, and government will promote and raise awareness of modern low vision rehabilitation for the benefit of all.
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paper_title: A review of current knowledge on Electronic Vision Enhancement Systems for the visually impaired.

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Magnification can be provided to assist those with visual impairment to make the best use of remaining vision. Electronic transverse magnification of an object was first conceived for use in low vision in the late 1950s, but has developed slowly and is not extensively prescribed because of its relatively high cost and lack of portability. Electronic devices providing transverse magnification have been termed closed-circuit televisions (CCTVs) because of the direct cable link between the camera imaging system and monitor viewing system, but this description generally refers to surveillance devices and does not indicate the provision of features such as magnification and contrast enhancement. Therefore, the term Electronic Vision Enhancement Systems (EVES) is proposed to better distinguish and describe such devices. This paper reviews current knowledge on EVES for the visually impaired in terms of: classification; hardware and software (development of technology, magnification and field-of-view, contrast and image enhancement); user aspects (users and usage, reading speed and duration, and training); and potential future development of EVES. © 2003 The College of Optometrists.
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paper_title: Effectiveness of Assistive Technologies for Low Vision Rehabilitation: A Systematic Review

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A systematic review of all types of assistive devices indicated the need for more research related to performance measurements and the effectiveness of vision rehabilitation devices. Low vision describes any condition of diminished vision that is uncorrectable by standard eyeglasses, contact lenses, medication, or surgery that disrupts a person's ability to perform common age-appropriate visual tasks (Jutai et al., 2007). Examples of assistive technolo- gies for vision rehabilitation include handheld magnifiers; electronic vision- enhancement systems; and mobility- related devices, such as long canes and night-vision systems. These types of de- vices and interventions allow individuals with low vision to lead productive lives and to maintain their independence in ev- eryday activities. In a large survey of pro- viders of low vision services, Elliott et al. (1997) found that for elderly patients with low vision, the primary objectives that were identified at the time of their assess- ments were to obtain help with reading
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paper_title: Global estimates of visual impairment: 2010

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AIM ::: From the most recent data the magnitude of visual impairment and its causes in 2010 have been estimated, globally and by WHO region. The definitions of visual impairment are the current definitions of presenting vision in the International Classification of Diseases version 10. ::: ::: ::: METHODS ::: A systematic review was conducted of published and unpublished surveys from 2000 to the present. For countries without data on visual impairment, estimates were based on newly developed imputation methods that took into account country economic status as proxy. ::: ::: ::: RESULTS ::: Surveys from 39 countries satisfied the inclusion criteria for this study. Globally, the number of people of all ages visually impaired is estimated to be 285 million, of whom 39 million are blind, with uncertainties of 10-20%. People 50 years and older represent 65% and 82% of visually impaired and blind, respectively. The major causes of visual impairment are uncorrected refractive errors (43%) followed by cataract (33%); the first cause of blindness is cataract (51%). ::: ::: ::: CONCLUSION ::: This study indicates that visual impairment in 2010 is a major health issue that is unequally distributed among the WHO regions; the preventable causes are as high as 80% of the total global burden.
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paper_title: Reading aids for adults with low vision

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BACKGROUND ::: The purpose of low-vision rehabilitation is to allow people to resume or to continue to perform daily living tasks, with reading being one of the most important. This is achieved by providing appropriate optical devices and special training in the use of residual-vision and low-vision aids, which range from simple optical magnifiers to high-magnification video magnifiers. ::: ::: ::: OBJECTIVES ::: To assess the effects of reading aids for adults with low vision. ::: ::: ::: SEARCH METHODS ::: We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2013, Issue 1), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE, (January 1950 to January 2013), EMBASE (January 1980 to January 2013), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to January 2013), OpenGrey (System for Information on Grey Literature in Europe) (www.opengrey.eu/), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov/) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 31 January 2013. We searched the reference lists of relevant articles and used the Science Citation Index to find articles that cited the included studies and contacted investigators and manufacturers of low-vision aids. We handsearched the British Journal of Visual Impairment from 1983 to 1999 and the Journal of Visual Impairment and Blindness from 1976 to 1991. ::: ::: ::: SELECTION CRITERIA ::: This review includes randomised and quasi-randomised trials in which any device or aid used for reading had been compared to another device or aid in people aged 16 or over with low vision as defined by the study investigators. ::: ::: ::: DATA COLLECTION AND ANALYSIS ::: At least two authors independently assessed trial quality and extracted data. ::: ::: ::: MAIN RESULTS ::: We included nine small studies with a cross-over-like design (181 people overall) and one study with three parallel arms (243 participants) in the review. All studies reported the primary outcome, results for reading speed.Two studies including 92 participants found moderate- or low-quality evidence suggesting that reading speed is higher with stand-mounted electronic devices or electronic devices with the camera mounted in a 'mouse' than with optical magnifiers, which in these trials were generally stand-mounted or, less frequently, hand-held magnifiers or microscopic lenses. In another study of 20 participants there was moderate-quality evidence that optical devices are better than head-mounted electronic devices (four types).There was low-quality evidence from three studies (93 participants) that reading using head-mounted electronic devices is slower than with stand-based electronic devices. The technology of electronic devices may have changed and improved since these studies were conducted.One study suggested no difference between a diffractive spectacle-mounted magnifier and either refractive (15 participants) or aplanatic (15 participants) magnifiers.One study of 10 people suggested that several overlay coloured filters were no better and possibly worse than a clear filter.A parallel-arm study including 243 participants with age-related macular degeneration found that custom or standard prism spectacles were no different from conventional reading spectacles, although the data did not allow precise estimates of performance to be made. ::: ::: ::: AUTHORS' CONCLUSIONS ::: There is insufficient evidence on the effect of different types of low-vision aids on reading performance. It would be necessary to investigate which patient characteristics predict performance with different devices, including costly electronic devices. Better-quality research should also focus on assessing sustained long-term use of each device. Authors of studies testing several devices on the same person should consider design and reporting issues related to their sequential presentation and to the cross-over-like study design.
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paper_title: The limitations imposed on reading by low vision aids.

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Introduction: The changes that occur in the reading eye movements of normally sighted readers were measured as they used hand magnifiers to identify how these devices contribute to the slow reading of visually-impaired patients. Methods: Subjects inexperienced in magnifier use read texts containing two sizes of print, using hand magnifiers of two different powers, held at two different eye-to-magnifier distances. The effect of magnification (up to 13.5x) and field-of-view (FOV) (2-45 characters) could be assessed independently. Results: Reading speed decreased with increasing magnification because the size of the saccades did not increase in proportion to the magnification: for a given level of magnification, decreasing the FOV and decreasing the viewing distance both reduce the size of the saccades even further. The overall reading speed is only slowed significantly when the FOV restriction is extreme (two characters' width). Conclusions: Two mechanisms seem to be used spontaneously by normally sighted readers to mitigate the limitation of reading speed created by the shortened saccades: head movement in the direction of reading and retinal image slip during fixation.
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paper_title: Psychophysics of reading—II. Low vision

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Very little is known about the effects of visual impairment on reading. We used psychophysical methods to study reading by 16 low-vision observers. Reading rates were measured for text scanned across the face of a TV monitor while varying parameters that are likely to be important in low vision: angular character size, number of characters in the field, number of dots composing each character, contrast polarity (white-on-black vs black-on-white text), and character spacing. Despite diverse pathologies and degrees of vision loss in our sample, several major generalizations emerged. There is a wide variation in peak reading rates among low-vision observers, but 64% of the variance can be accounted for by two major distinctions: intact central fields vs central-field loss and cloudy vs clear ocular media. Peak reading rates for observers with central-field loss were very low (median 25 words/minute), while peak reading rates for observers with intact central fields were at least 90 words/minute (median 130 words/minute). Most low-vision readers require magnification to obtain characters of optimal size. Sloan M acuity was a better predictor of optimal character size than Snellen acuity, accounting for 72% of the variance. Low-vision reading is similar to normal reading in several respects. For example, both show the same dependence on the number of characters in the field. Our results provide estimates of the best reading performance to be expected from low-vision observers with characteristic forms of vision loss, and the stimulus parameters necessary for optimal performance. These results will be useful in the development of clinical tests of low vision, and in the design of low-vision reading aids.
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paper_title: Measuring perceived video quality of MPEG enhancement by people with impaired vision

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We used a new method to measure the perceived quality of contrast-enhanced motion video. Patients with impaired vision (n=24) and normally sighted subjects (n=6) adjusted the level of MPEG-based enhancement of 8 videos (4 min each) drawn from 4 categories. They selected the level of enhancement that provided the preferred view of the videos, using a decreasing-step-size staircase procedure. Most patients made consistent selections of the preferred level of enhancement, indicating an appreciation of and a perceived benefit from the MPEG-based enhancement. The selections varied between patients and were correlated with letter contrast sensitivity, but the selections were not affected by training, experience, or video category. We measured just noticeable differences directly for videos and mapped the image manipulation (enhancement in our case) onto an approximately linear perceptual space. These tools and approaches will be of value in other evaluations of the image quality of motion video manipulations.
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paper_title: Image enhancement in the JPEG domain for people with vision impairment

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An image enhancement algorithm for low-vision patients was developed for images compressed using the JPEG standard. The proposed algorithm enhances the images in the discrete cosine transform domain by weighting the quantization table in the decoder. Our specific implementation increases the contrast at all bands of frequencies by an equal factor. The enhancement algorithm has four advantages: 1) low computational cost; 2) suitability for real-time application; 3) ease of adjustment by end-users (for example, adjusting a single parameter); and 4) less severe block artifacts as compared with conventional (post compression) enhancements. Experiments with visually impaired patients show improved perceived image quality at moderate levels of enhancement but rejection of artifacts caused by higher levels of enhancement.
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paper_title: MPEG-based image enhancement for the visually impaired

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An MPEG-based image contrast enhancement algorithm for people with low vision is presented. Contrast enhancement is achieved by modifying the inter- and intra-quantization matrices in the MPEG decoder during the decompression stage. The algorithm has low computational complexity and does not affect the MPEG compressibility of the original image. We propose an enhancement filter based on the visual characteristics of low-vision patients, and report the results of preference experiments with 24 visually impaired subjects. Subjects favored low to moderate levels of enhancement for two of the tested video sequences, but favored only low levels of enhancement and rejected higher enhancement for two other sequences that had fast motion.
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paper_title: Enhancement of Text for the Visually Impaired

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Previous research has established the benefits of image enhancement by spatial filtering for face perception and motion video appreciation among elderly low-vision observers [ Invest. Ophthalmol. Vis. Sci.32, 2337 ( 1991); J. Opt. Soc. Am. A11, 1929 ( 1994)]. It has also been reported that similar enhancement could increase reading speeds by a factor of 2–4 in the same population [cf. Ophthalmology96, 115 ( 1989)]. In our experiments we sought to determine what benefit, if any, was derived from spatial filtering of text for low-vision readers. Results from this series of studies indicate that 66% of patients do increase their reading rate with enhancement, but this increase is small. Change in reading rate with spatial filtering ranged from a 100% decrement to a 125% improvement, with an average 13% improvement. Only 10 of 67 subjects increased their reading rates by 50% or more. The clinical information that we gathered does not allow us to predict accurately which patients will benefit from spatial filtering. On the basis of these findings we conclude that enhancement of text by spatial filtering does not substantially increase reading rates for most low-vision patients.
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paper_title: Generic and customised digital image enhancement filters for the visually impaired

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Abstract This study compares the effectiveness of various image enhancement filters for improving the perceived visibility of coloured digital natural images for people with visual impairment. Generic filters were compared with Peli’s adaptive enhancement and adaptive thresholding and custom-devised filters based on each subject’s contrast sensitivity loss. Subjects with low vision made within filter rankings followed by between filter ratings. In general, subjects preferred filters with lower gains. Unsharp masking resulted in a significant increase in perceived visibility for some image types ( p ⩽ 0.05) while Peli’s adaptive enhancement, edge enhancement and histogram equalization resulted in borderline improvements. Adaptive thresholding and the custom devised filter did not result in overall improvements in perceived visibility.
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paper_title: Image enhancement improves reading performance in age-related macular degeneration patients

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We wanted to determine whether the 2- to 4-fold increases in reading speed found for patients with age-related macular degeneration (ARMD) when reading filtered text, presented one word at a time in the middle of the display would also be found when filtered text was scrolled across the screen. Reading speeds for filtered text that compensates for an observer's reduced contrast sensitivity function (CSF) were compared with the reading speeds for unfiltered text, when continuous, non-repeating text was scrolled across the display. The reading speeds of the ARMD observers tested were 1.7-4.5-times faster when reading filtered text, than when reading unfiltered text that was scrolled across the screen. The largest increments, over a 4-fold increase, were obtained in those subjects with the lowest unfiltered reading rates and the greatest loss of central vision. This study illustrates the usefulness of individualized text filtering for image enhancement in digitally based viewing devices to provide low vision remediation.
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paper_title: Digital enhancement of television signals for people with visual impairments: Evaluation of a consumer product

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— Technology to improve the clarity of video for home-theater viewers is available utilizing a low-cost enhancement chip (DigiVision DV1000). The impact of such a device on the preference for enhanced video was tested for people with impaired vision and normally sighted viewers. Viewers with impaired vision preferred the enhancement effects more than normally sighted viewers. Preference for enhancement was correlated with loss in contrast sensitivity and visual acuity. Preference increased with increased enhancement settings (designed for those with normal vision) in the group with vision impairments. This suggests that higher enhancement levels may be of even greater benefit, and a similar product could be designed to meet the needs of the large, growing population of elderly television viewers with impaired vision.
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paper_title: Image Enhancement for the Visually Impaired: The Effects of Enhancement on Face Recognition

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Image enhancement has been shown to improve face recognition by visually impaired observers. We conducted three experiments in an effort to refine our understanding of the parameters leading to this effect. In experiment 1 we found that the band of spatial frequencies between 4 and 8 cycles/face is critical for face recognition. In experiment 2 we found that enhancement of these frequencies and the resulting image distortion actually reduced recognition performance for normal observers. Since the degradation of performance by low vision is larger than the effect of distortion, the enhancement that reduces performance for normal observers may still be beneficial for the visually impaired observer. Experiment 3 found that patients tend to prefer images enhanced at frequencies higher than the critical frequencies found in experiment 1. Such individually selected enhancement did not improve recognition in comparison with uniformly applied enhancement. The lack of an enhancement effect may be due to the small variability in enhancement frequencies selected by our subject population.
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paper_title: Quantitative assessment of perceived visibility enhancement with image processing for single face images: a preliminary study.

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PURPOSE. To develop a method to quantitatively assess the visibility enhancement of single face images gained with digital filters for people with maculopathy. To apply this method to obtaining preliminary results of visibility enhancement with subjectively preferred filters for people with maculopathy. METHODS. Six subjects with normal vision and two with maculopathy were required to recognize seven facial expressions of single face images with different display durations of 2 seconds, 1 second, and 0.73 second. As a result, four facial expressions (anger, disgust, fear, and sadness) and a display duration of 0.73 second were chosen to measure single face image visibility enhancement with subjectively preferred digital filters. Finally, nine subjects with maculopathy viewed 30 images with four facial expressions that were either unfiltered or filtered with subjectively preferred digital filters. Each subject was required to identify the facial expression in a four-alternative, forced-choice paradigm. The errors with original and filtered images were calculated. RESULTS. The method with four facial expressions and display duration of 0.73 second prevented a ceiling effect. The nine subjects with maculopathy made significantly fewer errors with the filtered images than with the original ones images (P = 0.004). CONCLUSIONS. The developed method was effective in objective (quantitative) measurement of the enhancement in image visibility with digital filtering for people with maculopathy. There is a measurable improvement in facial expression recognition with subjectively preferred filters. The facial expression recognition task developed and validated in the present study is recommended as a method to be used in future studies of enhancement of face images.
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paper_title: Image enhancement for the visually impaired

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Image enhancement as an aid for the visually impaired may improve visibility of TV programs and provide portable visual aid. This paper describes the current techniques for image enhancement and their underlying models. The limitations of the various techniques and of potential methods of implementation are high-lighted. Initial work in this area was based on a linear model. The finite dynamic range available in the video display and contamination of the enhanced image by high spatial frequency noise limited the model's usefulness. I propose a method to address some limitations of the original model that considers the nonlinear response of the visual system and requires enhancement of subthreshold spatial information only. This modification may increase the dynamic range available by decreasing the range previously used by the linear models to enhance visible details. However, for the modified technique to be most effective, the enhancement has to be continuously tuned, based on the patient's visual loss and the spatial frequency content of the displayed images. The implications of these limitations for the potential implementation in TV are discussed. Implementation of an image-enhancing visual aid in a head-mounted, binocular, full-field, virtual vision device may cause substantial difficulties. Patient adaptation may be difficult due to head movement and interaction of the vestibular system response with the head-mounted display. An alternate, bioptic design is proposed in which the display is positioned above or below the line of sight to be examined intermittently, possibly in a freeze-frame mode. Such implementation is also likely to be less expensive, enabling more users access to the device.
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paper_title: Custom-devised and generic digital enhancement of images for people with maculopathy

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AIM ::: The purpose of this study was to compare the effectivity, in terms of the potential usefulness, of digital filters based on either contrast sensitivity (CS) or supra-threshold contrast matching (CM) in enhancing pictures images for people with maculopathy and to investigate whether generic filters (not based on an individual's vision loss) are equally as effective. Effectivity is measured by changes in perceived visibility. ::: ::: ::: METHODS ::: Thirty-five subjects with maculopathy, aged 20-92 years, took part [13 atrophic age-related macular degeneration (ARMD), 14 exudative ARMD, and 8 juvenile macular dystrophy (JMD)]. CS and supra-threshold CM were measured. A range of CS filters (1 or 2-octave wide band-pass filter using a Gabor or polynomial envelope) with different strengths were developed based on the ratio of the individual's contrast threshold and that of a normal age-related group. Similarly filters were developed based on CM at 3.6% and 27.9% contrast. The following generic filters were also applied with different 'strengths': edge enhancement; sharpening; contrast enhancement; Peli's adaptive enhancement; difference of Gaussian; and an equi-emphasis band-pass filter. The filters were applied to images of faces and general scenes. Subjects were asked to rank the perceived visibility of images (to obtain the best version of each filter) and then to rate the perceived visibility of each image filtered with a particular filter. ::: ::: ::: RESULTS ::: In general, subjects with atrophic ARMD and JMD preferred the weaker versions of most of the filters, while those with exudative ARMD did not show such a clear preference. Generally, images of faces were preferred with less enhancement than scenes. The filters based on CM were rated as giving significant improvement, while those based on CS and peak emphasis were not preferred. Of the generic filters, the Peli adaptive enhancement filter was most frequently rated as giving a significant improvement (p < 0.05) followed by the contrast enhancement filter. They gave the same perceived enhancement as the custom-devised filters. ::: ::: ::: CONCLUSIONS ::: Generic filters, which are easier to apply than the custom-devised filters, are appropriate for rehabilitation purposes.
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paper_title: Image enhancement filters significantly improve reading performance for low vision observers

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As people age, so do their photoreceptors; many photoreceptors in central vision stop functioning when a person reaches their late sixties or early seventies. Low vision observers with losses in central vision, those with age-related maculopathies, were studied. Low vision observers no longer see high spatial frequencies, being unable to resolve fine edge detail. We developed image enhancement filters to compensate for the low vision observer's losses in contrast sensitivity to intermediate and high spatial frequencies. The filters work by boosting the amplitude of the less visible intermediate spatial frequencies. The lower spatial frequencies. These image enhancement filters not only reduce the magnification needed for reading by up to 70%, but they also increase the observer's reading speed by 2-4 times. A summary of this research is presented.
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paper_title: Improved Reading Performance Using Individualized Compensation Filters for Observers with Losses in Central Vision

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Abstract By boosting the amplitudes of the intermediate spatial frequencies more than the amplitude of the lower spatial frequencies, reading performance improved significantly when observers with losses in central vision read words that were filtered. Words that were filtered using an image enhancement function based on an observer's losses in visual function relative to a normal observer (1) reduced the magnification (30–70% less magnification was needed) and (2) increased the reading rate (2–3 times), measured in words per minute. The greater the loss in central visual function, the more individualized compensation filters reduced the magnification needed for word recognition. Individualized compensation filters improved the clarity and visibility of words for low vision observers. This study also found that the shape of the enhancement function was important to determine the optimum compensation filter for improving reading performance. In addition, the individualized compensation filters can be implemented by inexpensive hardware, for example in a closed circuit television (CCTV), to provide a significantly more effective low vision aid for observers with losses in central vision to read text, than is provided using only magnification.
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paper_title: Head-mounted mobility aid for low vision using scene classification techniques

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This paper describes a new mobility aid for people with severe visual impairments which combines technology from the field of virtual reality with advanced computer vision techniques. A neural-network classifier is used to identify objects in images from a head mounted camera so that scene content specifically important for mobility may be made more visible. Enhanced images are displayed to the user on a head mounted display using a high saturation colour scheme where each type of object has a different colour, resulting in images which are highly visible and easy to interpret. The object classifier achieves a level of accuracy over 90%. Results from a pilot study conducted using people with a range of visual impairments are presented in which performance on a difficult mobility-related task was improved by over 100% using the system.
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paper_title: Collision Judgment When Using an Augmented-Vision Head-Mounted Display Device

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PURPOSE ::: A device was developed to provide an expanded visual field to patients with tunnel vision by superimposing minified edge images of the wide scene, in which objects appear closer to the heading direction than they really are. Experiments were conducted in a virtual environment to determine whether users would overestimate collision risks. ::: ::: ::: METHODS ::: Given simulated scenes of walking or standing with intention to walk toward a given direction (intended walking) in a shopping mall corridor, participants (12 normally sighted and 7 with tunnel vision) reported whether they would collide with obstacles appearing at different offsets from variable walking paths (or intended directions), with and without the device. The collision envelope (CE), a personal space based on perceived collision judgments, and judgment uncertainty (variability of response) were measured. When the device was used, combinations of two image scales (5x minified and 1:1) and two image types (grayscale or edge images) were tested. ::: ::: ::: RESULTS ::: Image type did not significantly alter collision judgment (P > 0.7). Compared to the without-device baseline, minification did not significantly change the CE of normally sighted subjects for simulated walking (P = 0.12), but increased CE by 30% for intended walking (P < 0.001). Their uncertainty was not affected by minification (P > 0.25). For the patients, neither CE nor uncertainty was affected by minification (P > 0.13) in both walking conditions. Baseline CE and uncertainty were greater for patients than normally sighted subjects in simulated walking (P = 0.03), but the two groups were not significantly different in all other conditions. ::: ::: ::: CONCLUSIONS ::: Users did not substantially overestimate collision risk, as the x5 minified images had only limited impact on collision judgments either during walking or before starting to walk.
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paper_title: Development and evaluation of vision multiplexing devices for vision impairment

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We have proposed a novel concept of vision multiplexing for the visually impaired – superimposing contour images over their natural view of a scene or over original images presented on a TV screen. We have implemented the concept using an optical see-through head mounted display to provide either visual field expansion to patients with peripheral field loss or vision enhancement to patients with central vision loss. We have also implemented the concept in a video player with dynamic magnification for patients with central vision loss. Results of initial testing in the lab and on the street are promising.
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paper_title: Visual Search with Image Modification in Age-Related Macular Degeneration

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PURPOSE ::: AMD results in loss of central vision and a dependence on low-resolution peripheral vision. While many image enhancement techniques have been proposed, there is a lack of quantitative comparison of the effectiveness of enhancement. We developed a natural visual search task that uses patients' eye movements as a quantitative and functional measure of the efficacy of image modification. ::: ::: ::: METHODS ::: Eye movements of 17 patients (mean age = 77 years) with AMD were recorded while they searched for target objects in natural images. Eight different image modification methods were implemented and included manipulations of local image or edge contrast, color, and crowding. In a subsequent task, patients ranked their preference of the image modifications. ::: ::: ::: RESULTS ::: Within individual participants, there was no significant difference in search duration or accuracy across eight different image manipulations. When data were collapsed across all image modifications, a multivariate model identified six significant predictors for normalized search duration including scotoma size and acuity, as well as interactions among scotoma size, age, acuity, and contrast (P < 0.05). Additionally, an analysis of image statistics showed no correlation with search performance across all image modifications. Rank ordering of enhancement methods based on participants' preference revealed a trend that participants preferred the least modified images (P < 0.05). ::: ::: ::: CONCLUSIONS ::: There was no quantitative effect of image modification on search performance. A better understanding of low- and high-level components of visual search in natural scenes is necessary to improve future attempts at image enhancement for low vision patients. Different search tasks may require alternative image modifications to improve patient functioning and performance.
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paper_title: A reconfigurable real-time morphological system for augmented vision

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There is a significant number of visually impaired individuals who suffer sensitivity loss to high spatial frequencies, for whom current optical devices are limited in degree of visual aid and practical application. Digital image and video processing offers a variety of effective visual enhancement methods that can be utilised to obtain a practical augmented vision head-mounted display device. The high spatial frequencies of an image can be extracted by edge detection techniques and overlaid on top of the original image to improve visual perception among the visually impaired. Augmented visual aid devices require highly user-customisable algorithm designs for subjective configuration per task, where current digital image processing visual aids offer very little user-configurable options. This paper presents a highly user-reconfigurable morphological edge enhancement system on field-programmable gate array, where the morphological, internal and external edge gradients can be selected from the presented architecture with specified edge thickness and magnitude. In addition, the morphology architecture supports reconfigurable shape structuring elements and configurable morphological operations. The proposed morphology-based visual enhancement system introduces a high degree of user flexibility in addition to meeting real-time constraints capable of obtaining 93 fps for high-definition image resolution.
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paper_title: Use of an augmented-vision device for visual search by patients with tunnel vision

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PURPOSE ::: To study the effect of an augmented-vision device that superimposes minified contour images over natural vision on visual search performance of patients with tunnel vision. ::: ::: ::: METHODS ::: Twelve subjects with tunnel vision searched for targets presented outside their visual fields (VFs) on a blank background under three cue conditions (with contour cues provided by the device, with auditory cues, and without cues). Three subjects (VF, 8 degrees -11 degrees wide) carried out the search over a 90 degrees x 74 degrees area, and nine subjects (VF, 7 degrees -16 degrees wide) carried out the search over a 66 degrees x 52 degrees area. Eye and head movements were recorded for performance analyses that included directness of search path, search time, and gaze speed. ::: ::: ::: RESULTS ::: Directness of the search path was greatly and significantly improved when the contour or auditory cues were provided in the larger and the smaller area searches. When using the device, a significant reduction in search time (28% approximately 74%) was demonstrated by all three subjects in the larger area search and by subjects with VFs wider than 10 degrees in the smaller area search (average, 22%). Directness and gaze speed accounted for 90% of the variability of search time. ::: ::: ::: CONCLUSIONS ::: Although performance improvement with the device for the larger search area was obvious, whether it was helpful for the smaller search area depended on VF and gaze speed. Because improvement in directness was demonstrated, increased gaze speed, which could result from further training and adaptation to the device, might enable patients with small VFs to benefit from the device for visual search tasks.
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paper_title: A Robust Edge Enhancement Approach for Low Vision Patients Using Scene Simplification

paper_content:

Patients with low vision have reduced visual acuity and a significant loss of contrast sensitivity resulting in gross blurring of the visual scene over a significant area of their field of view. This paper describes a robust approach for edge enhancement for visual impairments patients, based on simplifying the visual scene to remove unnecessary textures and then enhance the edges of the simplified image. The effectiveness of this scheme was demonstrated in a pilot study composed of three patients suffering from macular degeneration. They succeeded to identify most of the objects in the images when using our robust enhancement compared to the original images.
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paper_title: Wideband Enhancement of Television Images for People with Visual Impairments

paper_content:

Wideband enhancement was implemented by detecting visually relevant edge and bar features in an image to produce a bipolar contour map. The addition of these contours to the original image resulted in increased local contrast of these features and an increase in the spatial bandwidth of the image. Testing with static television images revealed that visually impaired patients (n = 35) could distinguish the enhanced images and preferred them over the original images (and degraded images). Most patients preferred a moderate level of wideband enhancement, since they preferred natural-looking images and rejected visible artifacts of the enhancement. Comparison of the enhanced images with the originals revealed that the improvement in the perceived image quality was significant for only 22% of the patients. Possible reasons for the limited increase in perceived image quality are discussed, and improvements are suggested.
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paper_title: Optoelectronic aid for patients with severely restricted visual fields in daylight conditions

paper_content:

In this study we evaluated the immediate effectiveness of an optoelectronic visual field expander in a sample of subjects with retinitis pigmentosa suffering from a severe peripheral visual field restriction. The aid uses the augmented view concept and provides subjects with visual information from outside their visual field. The tests were carried out in daylight conditions. The optoelectronic aid comprises a FPGA (real-time video processor), a wide-angle mini camera and a transparent see-through head-mounted display. This optoelectronic aid is called SERBA (Sistema Electro-optico Reconfigurable de Ayuda para Baja Vision). We previously showed that, without compromising residual vision, the SERBA system provides information about objects within an area about three times greater on average than the remaining visual field of the subjects [1]. In this paper we address the effects of the device on mobility under daylight conditions with and without SERBA. The participants were six subjects with retinitis pig...
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paper_title: Image enhancement of real-time television to benefit the visually impaired.

paper_content:

PURPOSE ::: To examine the use of real-time, generic edge detection, image processing techniques to enhance the television viewing of the visually impaired. ::: ::: ::: DESIGN ::: Prospective, clinical experimental study. ::: ::: ::: METHOD ::: One hundred and two sequential visually impaired (average age 73.8 +/- 14.8 years; 59% female) in a single center optimized a dynamic television image with respect to edge detection filter (Prewitt, Sobel, or the two combined), color (red, green, blue, or white), and intensity (one to 15 times) of the overlaid edges. They then rated the original television footage compared with a black-and-white image displaying the edges detected and the original television image with the detected edges overlaid in the chosen color and at the intensity selected. Footage of news, an advertisement, and the end of program credits were subjectively assessed in a random order. ::: ::: ::: RESULTS ::: A Prewitt filter was preferred (44%) compared with the Sobel filter (27%) or a combination of the two (28%). Green and white were equally popular for displaying the detected edges (32%), with blue (22%) and red (14%) less so. The average preferred edge intensity was 3.5 +/- 1.7 times. The image-enhanced television was significantly preferred to the original (P < .001), which in turn was preferred to viewing the detected edges alone (P < .001) for each of the footage clips. Preference was not dependent on the condition causing visual impairment. Seventy percent were definitely willing to buy a set-top box that could achieve these effects for a reasonable price. ::: ::: ::: CONCLUSIONS ::: Simple generic edge detection image enhancement options can be performed on television in real-time and significantly enhance the viewing of the visually impaired.
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paper_title: A versatile optoelectronic aid for low vision patients

paper_content:

The purpose of this work is to describe a versatile optoelectronic aid for low vision rehabilitation based on reconfigurable hardware. This aid is easily adaptable to diverse pathologies (with different associated processing tasks) and to the progression of the visual impairment. This platform has a mobile configuration that uses a see-through head-mounted display (Nomad). We have implemented different types of vision enhancement on this versatile platform, and briefly summarize here their computational costs (in terms of hardware resource requirements). We have evaluated two representative capabilities of this aid (Augmented View and digital zoom) with measurements of visual acuity, contrast sensitivity and visual field. We have tested the Nomad head-mounted display and the Augmented View modality, in eight subjects with retinitis pigmentosa: the digital zoom was tested in six low vision subjects and nine normally-sighted subjects. We show that the Nomad display with Augmented View configuration does not impair the residual vision; and that there is an increase in visual acuity (VA) with the digital zoom configuration. The major advantage of this platform is that it can easily embed different image processing tasks and since it is based on a FPGA device, it can be specifically configured to tasks requiring real-time processing.
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paper_title: An Augmented-Reality Edge Enhancement Application for Google Glass

paper_content:

Most patients with advanced age-related macular degeneration (AMD) experience reduced visual acuity (VA) and contrast sensitivity (CS) because they have to rely on the residual non-foveal retina to inspect targets of interest. Although patients’ peri-peripheral vision is sufficient to recognize the gist of scenes,1 their quality of life is significantly affected by the impairment.2–4 The reduced visual function has a large impact on emotional well-being,5 and social engagement,6 especially due to its effect on tasks such as face recognition,7, 8 which require the ability to discriminate fine details or small contrast differences. ::: ::: The low vision enhancement system (LVES) was the first such commercial system for distance use, utilizing an opaque head mounted display (HMD). It improved visual acuity and contrast sensitivity by converting the camera image into high contrast-magnified video.9 Later, video-based contrast enhancement and zoom-controlling HMD devices were commercialized, as the Jordy (Enhanced vision, CA, USA) and the SightMate (Vuzix, NY, USA). All these devices use full virtual vision HMDs that block the wearer’s natural field of vision. ::: ::: An alternative approach, augmented reality (AR) using optical see-through HMDs, was proposed by Peli for various vision conditions,10 for example, employing wideband image enhancement to enhance the visibility of edges of the scene, as an alternative to magnification.11, 12 Luo and Peli developed a hybrid see-through/opaque HMD device that superimposed a scene edge-view over the wearer’s natural view in see-through mode, but the display could be made opaque to display only a magnified scene edge-view.13, 14 Using desktop displays, it has been shown that adding high contrast edges to static images,15 or videos16 is preferred by patients with AMD,15, 16 and improved visual search performance of elderly with simulated central visual loss.15, 17 ::: ::: Precise alignment of the augmented edges with the see-through scene is necessary, but difficult to achieve in the HMD application, because the camera and the display are usually shifted relative to each other. The parallax produced by that shift varies with distance to the objects of regard. An on-axis HMD-camera configuration was attempted and achieved excellent edge alignment, but the optical system aligning the camera and display reduced display brightness to such an extent that the augmented edges were too dim to provide a significant boost in visibility.18 ::: ::: Google Inc. (Mountain View, CA) has recently introduced a novel HMD system, Google Glass, which is intended for an interactive personal communication device. Glass provides a hardware and software development platform that can be applied to vision enhancement for patients with impaired vision. It features a wide-field high-resolution camera, a small optical see-through display positioned above the line of sight, a rechargeable battery, and enough computing power for image processing. The Android-based operating system, which is open for custom app development, supports OpenGL GPU computations and camera access. ::: ::: Here, we report a preliminary exploration of the utility of Google Glass as a visual aid for patients with AMD by developing an app that provides edge enhancement as an augmented view. The real view of the environment through the Glass display is multiplexed with a scaled cartoonized outline of the view, captured by the camera. The user sees enhanced contrast at the location of edges in the real-world. We show how the spatial alignment problem between the augmented edges and the real view can be addressed to provide such an augmented view. We also describe how we generate and display augmented edge information, where the edge enhancement method and range of enhancement is user selectable, because optimal settings of these factors depend on the individual user’s impairment and the immediate task that the user anticipates, as well as the visual and environment and lighting conditions. The user interface for controlling system parameters must be simple, intuitive, and quick.
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paper_title: Contour Enhancement Benefits Older Adults with Simulated Central Field Loss

paper_content:

Purpose. Age-related macular degeneration is the leading cause of vision loss among Americans aged 65 years. Currently, no effective treatment can reverse the central vision loss associated with most age-related macular degeneration. Digital image-processing techniques have been developed to improve image visibility for peripheral vision; however, both the selection and efficacy of such methods are limited. Progress has been difficult for two reasons: the exact nature of image enhancement that might benefit peripheral vision is not well understood, and efficient methods for testing such techniques have been elusive. The current study aims to develop both an effective image enhancement technique for peripheral vision and an efficient means for validating the technique. Methods. We used a novel contour-detection algorithm to locate shape-defining edges in images based on natural-image statistics. We then enhanced the scene by locally boosting the luminance contrast along such contours. Using a gaze-contingent display, we simulated central visual field loss in normally sighted young (aged 18–30 years) and older adults (aged 58–88 years). Visual search performance was measured as a function of contour enhancement strength [“Original” (unenhanced), “Medium,” and “High”]. For preference task, a separate group of subjects judged which image in a pair “would lead to better search performance.” Results. We found that although contour enhancement had no significant effect on search time and accuracy in young adults, Medium enhancement resulted in significantly shorter search time in older adults (about 13% reduction relative to Original). Both age-groups preferred images with Medium enhancement over Original (2–7 times). Furthermore, across age-groups, image content types, and enhancement strengths, there was a robust correlation between preference and performance. Conclusions. Our findings demonstrate a beneficial role of contour enhancement in peripheral vision for older adults. Our findings further suggest that task-specific preference judgments can be an efficient surrogate for performance testing. (Optom Vis Sci 2012;89:1374–1384)
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paper_title: Visual Search with Image Modification in Age-Related Macular Degeneration

paper_content:

PURPOSE ::: AMD results in loss of central vision and a dependence on low-resolution peripheral vision. While many image enhancement techniques have been proposed, there is a lack of quantitative comparison of the effectiveness of enhancement. We developed a natural visual search task that uses patients' eye movements as a quantitative and functional measure of the efficacy of image modification. ::: ::: ::: METHODS ::: Eye movements of 17 patients (mean age = 77 years) with AMD were recorded while they searched for target objects in natural images. Eight different image modification methods were implemented and included manipulations of local image or edge contrast, color, and crowding. In a subsequent task, patients ranked their preference of the image modifications. ::: ::: ::: RESULTS ::: Within individual participants, there was no significant difference in search duration or accuracy across eight different image manipulations. When data were collapsed across all image modifications, a multivariate model identified six significant predictors for normalized search duration including scotoma size and acuity, as well as interactions among scotoma size, age, acuity, and contrast (P < 0.05). Additionally, an analysis of image statistics showed no correlation with search performance across all image modifications. Rank ordering of enhancement methods based on participants' preference revealed a trend that participants preferred the least modified images (P < 0.05). ::: ::: ::: CONCLUSIONS ::: There was no quantitative effect of image modification on search performance. A better understanding of low- and high-level components of visual search in natural scenes is necessary to improve future attempts at image enhancement for low vision patients. Different search tasks may require alternative image modifications to improve patient functioning and performance.
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paper_title: Image processing to facilitate image identification by partially-sighted

paper_content:

Abstract A previous study from our laboratory demonstrates that central visual field loss produces interference in identifying objects embedded in textured backgrounds. These results motivated us to investigate segmentation algorithms that would permit separate treatment of figure and ground, in order to enhance selectively the identifiability of objects. The segmentation algorithms that we used are based on coding the image as a “steerable pyramid,” e.g., of Portilla and Simoncelli or with Liu's spectral histogram method. These methods allow us to define a profile of different areas of an image based upon textural properties related to orientation and spatial frequency differences, which then serve as criteria for figure/ground segmentation. In order to verify the previous results, we evaluated the minimal bandwidth for identification with pre-segmented and unsegmented images in AMD patients and in foveal vision of normal controls. A real-time image-processing tool could be a valuable visual aid for partially-sighted observers.
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paper_title: Influence of background on image recognition in normal vision and age-related macular degeneration

paper_content:

PURPOSE ::: The influence of background attenuation on the spatial frequency bandwidth requirements for image recognition was assessed in normal young and older groups and in a group with age-related macular degeneration (AMD). Bandwidth requirements were also assessed in the visual periphery of young normal observers. ::: ::: ::: METHODS ::: In Experiment 1, each observer was presented with 20 series of images. Each series consisted of a sequence of progressively low-pass filtered images, presented in an order of increasing bandwidth, i.e., according to an ascending method of limits. For half of the series, the background of the base image was selectively darkened by 80% of its original luminance. Three measures were analyzed: (1) the critical bandwidth defined as the bandwidth in cycles/image (cpi) at which 50% of the images were recognized, (2) the minimal bandwidth, defined as the minimal bandwidth at which images were recognized and (3) the proportion of images recognized at full bandwidth. In Experiment 2, young normal observers were similarly tested in central vision and at 5.5° eccentricity (superior or inferior visual field). A third background attenuation condition was included, as well, in which the background was low-pass filtered. ::: ::: ::: RESULTS ::: The critical bandwidth for image recognition was significantly reduced by darkening the image background for normal young and old and the AMD groups. This improvement was found to be contrast dependent for the darkened background. In addition, AMD observers tended to recognize more images at full bandwidth if the background was darkened. For normal young observers, making the background low-pass was ineffective in lowering the critical bandwidth in the fovea. Fewer images were recognized at full bandwidth at 5.5° eccentricity for a low-pass background and marginally fewer for a darkened background. ::: ::: ::: CONCLUSIONS ::: Selective attenuation of the image background can lead to reductions in the bandwidth requirements for image recognition in AMD. However, performance of young normal observers for images presented in the periphery was unlike AMD performance under the conditions investigated. These results have interesting implications for the design of image enhancement algorithms to aid low vision observers.
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paper_title: Designing and testing scene enhancement algorithms for patients with retina degenerative disorders

paper_content:

BackgroundRetina degenerative disorders represent the primary cause of blindness in UK and in the developed world. In particular, Age Related Macular Degeneration (AMD) and Retina Pigmentosa (RP) diseases are of interest to this study. We have therefore created new image processing algorithms for enhancing the visual scenes for them.MethodsIn this paper we present three novel image enhancement techniques aimed at enhancing the remaining visual information for patients suffering from retina dystrophies. Currently, the only effective way to test novel technology for visual enhancement is to undergo testing on large numbers of patients. To test our techniques, we have therefore built a retinal image processing model and compared the results to data from patient testing. In particular we focus on the ability of our image processing techniques to achieve improved face detection and enhanced edge perception.ResultsResults from our model are compared to actual data obtained from testing the performance of these algorithms on 27 patients with an average visual acuity of 0.63 and an average contrast sensitivity of 1.22. Results show that Tinted Reduced Outlined Nature (TRON) and Edge Overlaying algorithms are most beneficial for dynamic scenes such as motion detection. Image Cartoonization was most beneficial for spatial feature detection such as face detection. Patient's stated that they would most like to see Cartoonized images for use in daily life.ConclusionsResults obtained from our retinal model and from patients show that there is potential for these image processing techniques to improve visual function amongst the visually impaired community. In addition our methodology using face detection and efficiency of perceived edges in determining potential benefit derived from different image enhancement algorithms could also prove to be useful in quantitatively assessing algorithms in future studies.
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paper_title: Head-mounted mobility aid for low vision using scene classification techniques

paper_content:

This paper describes a new mobility aid for people with severe visual impairments which combines technology from the field of virtual reality with advanced computer vision techniques. A neural-network classifier is used to identify objects in images from a head mounted camera so that scene content specifically important for mobility may be made more visible. Enhanced images are displayed to the user on a head mounted display using a high saturation colour scheme where each type of object has a different colour, resulting in images which are highly visible and easy to interpret. The object classifier achieves a level of accuracy over 90%. Results from a pilot study conducted using people with a range of visual impairments are presented in which performance on a difficult mobility-related task was improved by over 100% using the system.
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paper_title: Improved content aware scene retargeting for retinitis pigmentosa patients

paper_content:

BackgroundIn this paper we present a novel scene retargeting technique to reduce the visual scene while maintaining the size of the key features. The algorithm is scalable to implementation onto portable devices, and thus, has potential for augmented reality systems to provide visual support for those with tunnel vision. We therefore test the efficacy of our algorithm on shrinking the visual scene into the remaining field of view for those patients.MethodsSimple spatial compression of visual scenes makes objects appear further away. We have therefore developed an algorithm which removes low importance information, maintaining the size of the significant features. Previous approaches in this field have included seam carving, which removes low importance seams from the scene, and shrinkability which dynamically shrinks the scene according to a generated importance map. The former method causes significant artifacts and the latter is inefficient. In this work we have developed a new algorithm, combining the best aspects of both these two previous methods. In particular, our approach is to generate a shrinkability importance map using as seam based approach. We then use it to dynamically shrink the scene in similar fashion to the shrinkability method. Importantly, we have implemented it so that it can be used in real time without prior knowledge of future frames.ResultsWe have evaluated and compared our algorithm to the seam carving and image shrinkability approaches from a content preservation perspective and a compression quality perspective. Also our technique has been evaluated and tested on a trial included 20 participants with simulated tunnel vision. Results show the robustness of our method at reducing scenes up to 50% with minimal distortion. We also demonstrate efficacy in its use for those with simulated tunnel vision of 22 degrees of field of view or less.ConclusionsOur approach allows us to perform content aware video resizing in real time using only information from previous frames to avoid jitter. Also our method has a great benefit over the ordinary resizing method and even over other image retargeting methods. We show that the benefit derived from this algorithm is significant to patients with fields of view 20° or less.
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paper_title: Methods study for the relocation of visual information in central scotoma cases

paper_content:

In this study we test the benefit on the reading performance of different ways to relocating the visual information present under the scotoma. The relocation (or unmasking) allows to compensate the loss of information and avoid the patient developing driving strategies not adapted for the reading. Eight healthy subjects were tested on a reading task, on each a central scotoma of various sizes was simulated. We then evaluate the reading speed (words/min) during three visual information relocation methods: all masked information is relocated - on both side of scotoma, - on the right of scotoma, - and only essentials letters for the word recognition too on the right of scotoma. We compare these reading speeds versus the pathological condition, ie without relocating visual information. Our results show that unmasking strategy improve the reading speed when all the visual information is unmask to the right of scotoma, this only for large scotoma. Taking account the word morphology, the perception of only certain letters outside the scotoma can be sufficient to improve the reading speed. A deepening of reading processes in the presence of a scotoma will then allows a new perspective for visual information unmasking. Multidisciplinary competences brought by engineers, ophtalmologists, linguists, clinicians would allow to optimize the reading benefit brought by the unmasking.
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paper_title: Reading rates with artificial central scotomata with and without spatial remapping of print

paper_content:

ABSTRACTPeople with central field defects resulting from agerelated macular degeneration (ARMD) read very slowly. In this study, oral reading rates were determined for unrelated sequences of words in samples of normal young and old subjects with simulated central scotomata of 20 40 and 80 Scotomata
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paper_title: Testing of remapping for reading enhancement for patients with central visual field losses

paper_content:

Retinal pathology often results in visual field loss. Age related macular degeneration (ARMD) and Stargardt's disease (a congenital disease) typically affects the central macular region of the retina, resulting in visual field loss to the region of the retina with the highest resolution. Due to the central visual field losses, patients with ARMD and Stargardt's disease often experience difficulty in visual tasks, such as reading and facial recognition. NASA Johnson Space Center has developed an electronic remapper that can warp an image from one coordinate system to another on a television screen. The remapper can be used with patients with central visual field loss to redistribute information projecting off of the macular lesion (corresponding to the central scotoma) and onto the still functioning peripheral retina. The purpose of this research project was to investigate whether remapping of text around the central scotoma improved reading performance (increased reading rate) for patients with ARMD or Stargardt's disease. The subjects moved the text on the stage and read aloud random words of equal difficulty viewed on a closed circuit television screen. Reading speeds for normal and remapped text were obtained. Reading rates were determined for both free viewing and with stabilization of the position of the screen relative to the eye rotations. Results of these experiments are discussed.
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paper_title: Image Jitter Enhances Visual Performance when Spatial Resolution Is Impaired

paper_content:

PURPOSE. Visibility of low–spatial frequency stimuli improves when their contrast is modulated at 5 to 10 Hz compared with stationary stimuli. Therefore, temporal modulations of visual objects could enhance the performance of low vision patients who primarily perceive images of low–spatial frequency content. We investigated the effect of retinal-image jitter on word recognition speed and facial emotion recognition in subjects with central visual impairment. METHODS. Word recognition speed and accuracy of facial emotion discrimination were measured in volunteers with AMD under stationary and jittering conditions. Computerdriven and optoelectronic approaches were used to induce retinal-image jitter with duration of 100 or 166 ms and amplitude within the range of 0.5 to 2.68 visual angle. Word recognition speed was also measured for participants with simulated (Bangerter filters) visual impairment. RESULTS. Text jittering markedly enhanced word recognition speed for people with severe visual loss (101 6 25%), while for those with moderate visual impairment, this effect was weaker (19 6 9%). The ability of low vision patients to discriminate the facial emotions of jittering images improved by a factor of 2. A prototype of optoelectronic jitter goggles produced similar improvement in facial emotion discrimination. Word recognition speed in participants with simulated visual impairment was enhanced for interjitter intervals over 100 ms and reduced for shorter intervals. CONCLUSIONS. Results suggest that retinal-image jitter with optimal frequency and amplitude is an effective strategy for enhancing visual information processing in the absence of spatial detail. These findings will enable the development of novel tools to improve the quality of life of low vision patients. (Invest Ophthalmol Vis Sci. 2012;53:6004–6010) DOI:
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paper_title: Repeatability of visual function measures in age-related macular degeneration

paper_content:

Purpose ::: To assess repeatability of visual function measures in patients with early, intermediate or late age-related macular degeneration (AMD) without active neovascular disease in the study eye, but active neovascular AMD in the fellow eye.
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paper_title: Image enhancement for impaired vision: The challenge of evaluation

paper_content:

With the aging of the population, the prevalence of eye diseases and thus of vision impairment is increasing. The TV watching habits of people with vision impairments are comparable to normally sighted people1, however their vision loss prevents them from fully benefiting from this medium. For over 20 years we have been developing video image-enhancement techniques designed to assist people with visual impairments, particularly those due to central retinal vision loss. A major difficulty in this endeavor is the lack of evaluation techniques to assess and compare the effectiveness of various enhancement methods. This paper reviews our approaches to image enhancement and the results we have obtained, with special emphasis on the difficulties encountered in the evaluation of the benefits of enhancement and the solutions we have developed to date.
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paper_title: Contour Enhancement Benefits Older Adults with Simulated Central Field Loss

paper_content:

Purpose. Age-related macular degeneration is the leading cause of vision loss among Americans aged 65 years. Currently, no effective treatment can reverse the central vision loss associated with most age-related macular degeneration. Digital image-processing techniques have been developed to improve image visibility for peripheral vision; however, both the selection and efficacy of such methods are limited. Progress has been difficult for two reasons: the exact nature of image enhancement that might benefit peripheral vision is not well understood, and efficient methods for testing such techniques have been elusive. The current study aims to develop both an effective image enhancement technique for peripheral vision and an efficient means for validating the technique. Methods. We used a novel contour-detection algorithm to locate shape-defining edges in images based on natural-image statistics. We then enhanced the scene by locally boosting the luminance contrast along such contours. Using a gaze-contingent display, we simulated central visual field loss in normally sighted young (aged 18–30 years) and older adults (aged 58–88 years). Visual search performance was measured as a function of contour enhancement strength [“Original” (unenhanced), “Medium,” and “High”]. For preference task, a separate group of subjects judged which image in a pair “would lead to better search performance.” Results. We found that although contour enhancement had no significant effect on search time and accuracy in young adults, Medium enhancement resulted in significantly shorter search time in older adults (about 13% reduction relative to Original). Both age-groups preferred images with Medium enhancement over Original (2–7 times). Furthermore, across age-groups, image content types, and enhancement strengths, there was a robust correlation between preference and performance. Conclusions. Our findings demonstrate a beneficial role of contour enhancement in peripheral vision for older adults. Our findings further suggest that task-specific preference judgments can be an efficient surrogate for performance testing. (Optom Vis Sci 2012;89:1374–1384)
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Title: High tech aids low vision: A review of image processing for the visually impaired

Section 1: Introduction
Description 1: Provide an overview of the diversity and categorization of low-vision aids, the limitations of traditional aids, and the emergence of advanced image processing techniques to optimize visual experience for the visually impaired.

Section 2: Methods
Description 2: Describe the systematic approach used to search and identify relevant studies in Web of Science and PubMed, including the criteria for inclusion and exclusion of studies.

Section 3: Results
Description 3: Summarize the findings from the literature review, detailing the studies that investigated image processing techniques for text, images, and video, and highlight key results and methodologies.

Section 4: Contrast Enhancement
Description 4: Discuss the basic and advanced techniques for enhancing image contrast and their effectiveness in improving visual performance for the visually impaired.

Section 5: Spatial Frequencies
Description 5: Explain the use of spatial frequency content in image processing to enhance important image features and review studies that have applied these techniques.

Section 6: Edge and Contour Enhancement
Description 6: Explore techniques that enhance edges and contours within images, including wideband enhancement and other edge detection methods, supported by study findings.

Section 7: Background Attenuation and Scene Simplification
Description 7: Outline methods for segmenting images and attenuating backgrounds, simplifying scenes to reduce visual clutter for easier object recognition, supported by research studies.

Section 8: Remapping and Retargeting
Description 8: Describe strategies for overcoming blind spots, such as remapping text and retargeting scenes for individuals with field loss, along with related research outcomes.

Section 9: Jitter
Description 9: Investigate the counterintuitive approach of using image jitter to improve word recognition and emotion identification in individuals with macular degeneration.

Section 10: Discussion Image Distortion Levels
Description 10: Reflect on the trade-offs between image distortion and visual information availability in enhancement techniques, emphasizing the need for adjustable settings for individual users.

Section 11: Experimental Design
Description 11: Critically assess the design and methodology of the reviewed experiments, discussing potential biases, limitations, and the importance of larger, more focused studies on real participants.

Section 12: Methods of Evaluation
Description 12: Explore the challenges in developing appropriate outcome measures for evaluating image processing techniques, including the reliability and validity of different performance metrics.

Section 13: Conclusion
Description 13: Summarize the current state of the field, emphasizing the need for robust clinical studies and multidisciplinary collaboration to translate image processing advancements into practical benefits for patients.