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Vision Diseases, Disorders & Definitions

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D Definitions

Diabetic retinopathy

Retinal changes accompanying long-standing diabetes mellitus. Early stage is background retinopathy. May advance to proliferative retinopathy, which includes the growth of abnormal new blood vessels (neovascularization). Leading cause of visual impairment among working-age Americans. Diabetes also can cause cataracts.

Dilated pupil

Enlarged pupil, resulting from contraction of the dilator muscle or relaxation of the iris sphincter. Occurs normally in dim illumination, or may be produced by eye-drops containing drugs (mydriatics) during an eye exam.


Unit designating the refractive power of a lens.

Diplopia, double vision

Perception of two images from one object.

Dry eye syndrome or dry eye

Corneal and conjunctival dryness due to deficient tear production, predominantly in older women. Can cause foreign body sensation, burning eyes, and erosion of conjunctival and corneal epithelium.


Portions of this page are excerpted from Dictionary of Eye Terminology, copyright 1990-2006 by Barbara Cassin and Triad Communications. Reprinted with permission.

Some of the information above is reprinted from the National Eye Institute, National Institutes of Health, and is for educational purposes only. Superior Vision strongly recommends eye exams as the best way to diagnose eye conditions and learn more about potential vision problems.