Glaucoma
What the test examines Eye drops used Physical contact with the eye Procedure
Tonometry Inner eye pressure Maybe Maybe Eye drops may be used to numb the eye . The examiner then uses a tonometer to measure the inner pressure of the eye through pressure applied by a puff of warm air or a tiny tool
Ophthalmoscopy ( dilated eye examination ) Shape and color of the optic nerve Yes No Eye drops are used to dilate the pupil . Using a small magnification device with a light on the end , the examiner can examine the magnified optic nerve
Perimetry ( visual field test ) Complete field of vision No No The patient looks straight ahead and is asked to indicate when light passes the patient 's peripheral field of vision . This allows the examiner to map the patient 's field of vision
Gonioscopy Angle in the eye where the iris meets the cornea Yes Yes Eye drops are used to numb the eye . A hand-held contact lens with a mirror is placed gently on the eye to allow the examiner to see the angle between the cornea and the iris
Pachymetry Thickness of the cornea No Yes The examiner places a pachymeter gently on the front of the eye to measure its thickness
Nerve fiber analysis Thickness of the nerve fiber layer Maybe Maybe Using one of several techniques , the nerve fibers are examined
Diagnosis
Optic nerve in advanced glaucoma disease Screening for glaucoma is usually performed as part of a standard eye examination performed by optometrists and ophthalmologists . Testing for glaucoma should include measurements of the intraocular pressure via tonometry , [ 42 ] anterior chamber angle examination or gonioscopy , and examination of the optic nerve to look for any visible damage to it , or change in the cup-to-disc ratio and also rim appearance and vascular change . A formal visual field test should be performed . The retinal nerve fiber layer can be assessed with imaging techniques such as optical coherence tomography , scanning laser polarimetry , and/or scanning laser ophthalmoscopy ( Heidelberg retinal tomogram ) . [ 43 ] [ 44 ] [ 45 ] Visual field loss is the most specific sign of the condition ; however , it occurs later in the condition . [ 46 ] Owing to the sensitivity of all methods of tonometry to corneal thickness , methods such as Goldmann tonometry should be augmented with pachymetry to measure the central corneal thickness ( CCT ) . A thicker-than-average cornea can result in a pressure reading higher than the 'true ' pressure whereas a thinner-than-average cornea can produce a pressure reading lower than the 'true ' pressure . Because pressure measurement error can be caused by more than just CCT ( i.e. , corneal hydration , elastic properties , etc . ) , it is impossible to 'adjust ' pressure measurements based only on CCT measurements . The frequency doubling illusion can also be used to detect glaucoma with the use of a frequency doubling technology perimeter . [ 47 ] Examination for glaucoma also could be assessed with more attention given to sex , race , history of drug use , refraction , inheritance and family history . [ 43 ]
Glaucoma is a group of eye diseases which result in damage to the optic nerve and cause vision loss. The most common type is open-angle glaucoma, in which the drainage angle for fluid within the eye remains open, with less common types including closed-angle glaucoma and normal-tension glaucoma. Open-angle glaucoma develops slowly over time and there is no pain. Peripheral vision may begin to decrease, followed by central vision, resulting in blindness if not treated. Closed-angle glaucoma can present gradually or suddenly. The sudden presentation may involve severe eye pain, blurred vision, mid-dilated pupil, redness of the eye, and nausea. Vision loss from glaucoma, once it has occurred, is permanent. Risk factors for glaucoma include increased pressure in the eye, a family history of the condition, and high blood pressure. For eye pressures, a value of greater than is often used, with higher pressures leading to a greater risk. However, some may have high eye pressure for years and never develop damage. Conversely, optic nerve damage may occur with normal pressure, known as normal-tension glaucoma. The mechanism of open-angle glaucoma is believed to be slow exit of aqueous humor through the trabecular meshwork, while in closed-angle glaucoma the iris blocks the trabecular meshwork.