Featured Article Children's Vision


Vision Diseases, Disorders & Definitions


A Defintions


Increase in focusing power of the eye to maintain a clear image as objects are moved closer. Due to the crystalline lens becoming less flexible as age increases, the result is a natural loss of accommodation (focusing power). This condition is called presbyopia.


Clearness of eyesight. The amount of acuity depends on the sharpness of images and the sensitivity of nerve elements in the retina.


Prescription strength of a plus lens which is used for near vision. A plus lens can be added to another lens such as a minus lens for distance vision.

Age-related macular degeneration or disease (AMD, ARMD):




AMD occurs in two forms: wet and dry.

Where is the Macula?


Macula Image
Image Courtesy: National Eye Institute, National Institutes of Health

What is wet AMD?




What is dry AMD?



Amblyopia or "lazy eye":


How common is amblyopia?


What causes amblyopia?


Learn more about Amblyopia

Anophthalmia and Microphthalmia

Other Names

Anophthalmos and microphthalmos, small eye syndrome.

What are anophthalmia and microphthalmia?

Anophthalmia and microphthalmia are often used interchangeably. Microphthalmia is a disorder in which one or both eyes are abnormally small, while anophthalmia is the absence of one or both eyes. These rare disorders develop during pregnancy and can be associated with other birth defects.

What causes anophthalmia and microphthalmia?

Causes of these conditions may include genetic mutations and abnormal chromosomes. Researchers also believe that environmental factors, such as exposure to X-rays, chemicals, drugs, pesticides, toxins, radiation, or viruses, increase the risk of anophthalmia and microphthalmia, but research is not conclusive. Sometimes the cause in an individual patient cannot be determined.

Learn more about Anophthalmia and Microphthalmia

Aqueous or aqueous humor or aqueous fluid:

Clear, watery fluid that fills the anterior and posterior chambers of the eye. Nourishes the cornea, iris, and lens and maintains intraocular pressure.


A type of refractive error. Optical defect in which refractive power of an eye is not uniform in all directions (meridians). A large amount may result in headache and significant blurring of images. This condition is typically correctible through a cylindrical power included into the lens design.


The alignment of the lens' cylindrical part; used for correcting astigmatism. This measurement is given in degrees. The values are typically from 90 degrees to 180 degrees.


