Vision Disorders Glossary

Amblyopia (often called "lazy eye") is a unilateral (occasionally bilateral) condition in which the best-corrected vision is poorer than 20/20 (6/6) in the absence of any obvious structural anomalies or ocular disease.

Astigmatism is another common vision disorder that usually occurs in conjunction with myopia. Astigmatism may also occur independently or with farsightedness when the cornea is unevenly shaped-somewhat like a football instead of a more rounded basketball. Astigmatism occurs when light passing through the uneven cornea is focused at more than one point within the eye. This causes people to experience blurry or uneven vision.

Cataract is a change in the structure of the crystalline lens which results in loss of light and therefore image transmission to the retina.

Conjunctivitis is an inflammation of the conjunctiva, a thin, transparent layer covering the surface of the inner eyelid and the front of the eye. It affects people of all ages.

Allergic Conjunctivitis Seasonal (hay fever conjunctivitis) accounts for the majority of allergic conjunctivitis cases. As its name suggests, it is related to specific pollens that spore during specific seasons. Symptoms generally include red, itchy, and watery eyes. People affected by hay fever and other seasonal allergies also experience symptoms involving the nose and throat.

Allergic Conjunctivitis Perennial a year-round allergic condition. These allergic responses are often related to animal dander, dust, or other allergens that are present in the environment year round. Symptoms are similar to seasonal allergic conjunctivitis: however, they tend to be milder.

Cytomegalovirus (CMV) is an opportunistic infection. About 50% of the general population and 90% of people with HIV carry CMV. A healthy immune system keeps this virus in check. When HIV or another disease weakens immune defenses, CMV can attack several parts of the body. The most common illness caused by CMV is retinitis.

Retinitis is the death of cells in the retina, the back of the eye. It can quickly cause blindness unless treated. CMV can spread throughout the body and infect several organs at once. The first signs of CMV retinitis are vision problems such as moving black spots. These are called "floaters." They may indicate an inflammation of the retina.

Diplopia (double vision) is a condition in which a single object is perceived as two.

Dry Eye is a common condition that occurs when the eyes do not produce enough tears to keep the eye wet and comfortable. Common symptoms of Dry Eye include feelings of stinging, burning, or scratchiness of the eyes, production of stringy mucus in the eyes and extreme irritation from smoke. Dry Eye can make it difficult or impossible to wear contact lenses. Dry Eye is normally associated with aging, because tear production decreases with age. Women after menopause are most afflicted. Dry Eye can also be associated with arthritis and accompanied by a dry mouth.

Endophthalmitis is an inflammation within the eye. Inflammations may be caused by organisms such as bacteria or may be sterile as in immune disorders. Endophthamistis usually is used to indicate an infectious disease as occasionally occurs as a complication of surgery.

Glaucoma is abnormally increased intraocular pressure resulting in optic nerve damage and loss of visual field.

Hyperopia (Farsightedness) is caused when the surface of the eye (or the eye itself) is either too flat or too short to properly focus incoming light rays on the retina. When this occurs, light is actually focused on a point behind the retina. Persons with hyperopia can see well at a distance, but nearby objects appear blurry.

Keratoconus is an abnormality of the eye where the cornea becomes deformed in the shape of a cone. This condition is a contraindication to (or strong reason against having) refractive surgery such as PRK or RK.

Macular Degeneration There are several types of macular degeneration, but the fastest growing form is age-related macular degeneration (AMD). Although it rarely causes total blindness, age-related macular degeneration robs those affected of their sharp central vision and can dim contrast sensitivity and color perception. It destroys the clear, "straight ahead" central vision.

Myopia (Nearsightedness) is one of the most common vision disorders in the U.S. It is estimated that 25% of the general population is nearsighted. Myopia occurs when the cornea (or surface of the eye) is too steep or elongated. This causes light rays to focus in front of the retina (or back portion of the eye). Persons with myopia experience blurred or fuzzy vision at a distance, but can see well at near distances, thus the term nearsighted.

Presbyopia "Old eye" is a condition in which the ability to accommodate for near vision falls off because of loss of elasticity of the crystalline lens of the eye and weakness of the ciliary muscle. The individual is no longer able to read clearly and requires reading glasses.

Ptygeria is a growth of scar tissue on the cornea. These lesions like pinguecula are caused by an ultraviolet burn to the surface layer or epithelium.

Spots and Floaters are small clumps of gel that form in the vitreous - the clear jelly-like fluid that fills the inside cavity of the eye. Although they appear to be in front of the eye, they are actually floating in the fluid inside the eye and are seen as shadows by the retina. They may appear as little dots, circles, lines or cobwebs and are normally caused by the aging process. Normally they are no cause for concern, but if they develop suddenly, you should consult your optometrist.