Dictionary of terms relating to
eyesight and vision

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General Binocular Vision Disorder

Inability to efficiently utilize and/or sustain binocular vision. Symptoms include eyestrain, headaches, decreased comprehension, inability to concentrate while reading, excessive tearing, and blurred vision. A patient will have difficulty with both base-in and base-out prisms. Vision therapy is an effective treatment option.

Glare test

This test will help you understand how your vision is affected under night driving situations. You have disability glare when a light source reduces your visual acuity. This means that even if you have close to 20/20 vision under normal conditions, you can become practically blind at night when faced with the headlights of an oncoming vehicle.

Graves' Disease

Graves' Disease is a type of autoimmune disease that causes over-activity of the thyroid gland, causing hyperthyroidism. This over-activity is also sometimes called "toxic diffuse goiter." The thyroid gland helps set the rate of metabolism, which is the rate at which the body uses energy. When the thyroid is too active, it makes more thyroid hormones than the body needs. High levels of thyroid hormones can cause side effects such as weight loss, rapid heart rate and nervousness. This is an uncommon disease


Tendency of the eyes to deviate from their normal position for visual alignment. This condition may be observed when one eye is covered.


The eyes are abnormally turned.

HTS Computerized Binocular Home Vision Therapy System

A computer program which is prescribed by an eye doctor. The computer program is for improving eye tracking, eye teaming, and/or eye focusing.


Farsightedness, an individual will have difficulty seeing clearly up close. Light entering the eye focuses behind the retina when the eye is at rest and is corrected with a plus lens. Vision therapy is not prescribed for hyperopia. Children, up to about the age of 8 years, are often farsighted. For a diagram, please click here.


A condition in which one eye has a tendency to point higher than the other eye, causing eyestrain. Sometimes improved by prisms in glasses.


Strabismus, where one eye is turned in an upward direction. More information.


A condition in which one eye has a tendency to point lower than the other eye. This condition may be observed when one eye is covered.


Strabismus, where one eye is turned in a downward direction. More information.

Hysterical Amblyopia

A non specific visual loss with an unknown cause. Upon examination the doctor is unable to find corroborating objective evidence of this abnormality. The most common symptom is an isolated visual acuity impairment, followed by combined visual acuity impairment and visual field constriction, and whereas an isolated visual field constriction occurred most infrequently. This vision loss may be due to anxiety or emotional repression. (See "Streff Syndrome")