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Eye Health Glossary

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saccade

Rapid eye movement that occurs when fixation is moved from one target to another.

schlemm's canal

See Canal of Schlemm.

sclera

White part of the eye. The sclera is opaque and made of very tough fibrous tissue, providing a supportive function to the structure of the eyeball.

scotoma

See Blind spot.

sign

Objective observation that is noted upon examination of the eye for eye disease. A combination of signs and symptoms is used to diagnose disease.

sjogren's syndrome

Chronic eye disease in which white blood cells attack the moisture-producing glands (eg. tear glands and salivary glands), resulting in severe dry eye symptoms. Classic symptoms of Sjogren's are dry eyes and a dry mouth. Learn more about Sjogren's and dry eye syndrome.

slit lamp

Specialized biomicroscope used by eyecare professionals to view the structures of the eye under variable magnification and illumination. Using different techniques, all layers of the cornea can be examined.

snellen eye chart

Standardized eye chart for measuring visual acuity. Since Hermann Snellen developed the eye chart in 1862, many new eye charts have been developed, but his measuring system for visual acuity is still in place today.

stereogram

A graphic image that is specially designed to give the illusion of three dimensions. Having difficulty seeing the picture in a stereogram? Learn different techniques for viewing stereograms.

stereopsis

Ability to see objects as three-dimensional objects. See Depth Perception for more information.

strabismus

A binocular vision problem in which the eyes are not aligned correctly. When one eye is turned out, it is called exotropia, and when one eye is turned in, it is called esotropia. Hypertropia, hypotropia, and cyclotropia are all examples of less common examples of strabismus.

stroma

The layer below the epithelium in the cornea. The stroma is a thick supportive layer made up mostly of collagen.

stye

Red nodule localized on either the upper or lower eyelid. A stye can be either a non-infectious chalazion, or a painful and infectious hordeolum.

superior oblique

The extraocular muscle (EOM) responsible for rotating the top of the eye towards the nose as well as turning the eye downward.

superior rectus

The extraocular muscle (EOM) responsible for turning the eye upward as well as rotating the top of the eye towards to nose.

symptom

Any self-perceived sensation that indicates abnormal processes occurring within the body. Examples of symptoms are: headache, vision loss, eye strain, and dry eyes. Symptoms are different than signs.

systemic lupus erythematosus

Chronic autoimmune disorder that can have a widespread effect on all organs of the body, but mainly the kidney and joints. One of the classic signs of SLE is a butterfly rash across the cheeks of the face.

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