Vision Disorders

Vision disorders are irregularities or abnormalities either of the eye, visual pathway, or brain, which affect one's ability to see. In healthy vision, visual acuity—often referred to as "20/20 vision"—develops rapidly by three to six months of age and generally decreases rapidly as people approach 45. Poor visual acuity is often correctable with glasses or contact lenses. However, many other factors affect human's ability to see—some preventable or correctable and others not. Vision disorders may manifest from refractive errors, defective eye muscles, cataracts, lens displacement, glaucoma, fundus conditions, color vision deficits, eyelid conditions, orbital diseases, eye injuries, and optic nerve and visual pathway damage.

When the axial length is longer than normal, distant objects appear blurry. This error is called myopia, or short-sightedness. Myopia can also be caused by irregular curvature of the cornea or lens, and is correctable with concave or negative lenses.

Astigmatism, irregular curvature of the cornea, causes blurred vision of objects both near and far. It may be regular, which means light rays fall on the retina in two different areas, or irregular, resulting from corneal damage which projects light onto many different points on the retina. The former is correctable with lenses, the latter is not. Sometimes the faulty component is the crystalline lens and in these instances the error is called lenticular astigmatism.

Glaucoma is a serious condition which, left undiagnosed and treated, will cause permanent blindness. Glaucoma is the unrelieved increase of intraocular pressure which acts like air in a tire. In a normal eye, pressure is maintained by the continuous production of aqueous humor, its movement through the pupil into the anterior chamber, and its drainage out of the chamber. When drainage is decreased or prevented, pressure inside the chamber increases.

These are complications commonly caused by other eye diseases such as iritis, injury, blockage to the retinal vein, or long-term use of steroid eye drops for other disorders.

This is primarily an age-related disorder resulting in deterioration and often distortion of vision. It is one of the leading causes of blindness in developed countries. There is no treatment; however, if detected early, laser treatment may prevent further degeneration.

Retinitis pigmentosa and macular dystrophy are degenerative disorders which appear to be hereditary, generally affect young children and adolescents, and cause night blindness, tunnel vision, slow deterioration of central vision, and increasing loss of sight. As yet, effective treatment has not been found.