Circulatory problems associated with diabetes mellitus eventually cause changes in the retina referred to as diabetic retinopathy. In addition to vascular damage, there is a yellowish, waxy exudate high in lipoproteins. With time, new blood vessels form and penetrate the vitreous humor, causing hemorrhage, detachment of the retina, and blindness.

Cataract

A cataract is an opacity (cloudiness) of the lens. Causes of cataract include disease, injury, chemicals, and exposure to physical forces, especially the ultraviolet radiation in sunlight. The cataracts that frequently appear with age may result from exposure to environmental factors in combination with degeneration attributable to aging. To prevent blindness, the cloudy lens must be removed surgically. Commonly, the anterior capsule of the lens is removed along with the cataract, leaving the posterior capsule in place (Fig. 2). In phacoemulsification, the lens is fragmented with high-frequency ultrasound and extracted through a small incision. Often, after cataract removal, an artificial intraocular lens (IOL) is implanted to compensate for the missing lens. Alternatively, the person can wear a contact lens or special glasses.

FIGURE 2. Cataract extraction surgeries. (A) Cross-section of normal eye anatomy. (B) Extracapsular lens extraction involves removing the lens but leaving the posterior capsule intact to receive a synthetic intraocular lens. (C) Intracapsular lens extraction involves removing the lens and lens capsule and implanting a synthetic intraocular lens in the anterior chamber.

Glaucoma

Glaucoma is an abnormal increase in pressure within the eyeball. It occurs when more aqueous humor is produced than can be drained away from the eye. There is pressure on blood vessels in the eye and on the optic nerve, leading to blindness. There are many causes of glaucoma, and screening for glaucoma should be a part of every routine eye examination. Fetal infection with German measles (rubella) early in pregnancy can cause glaucoma, as well as cataracts and hearing impairment. Glaucoma is usually treated with medication to reduce pressure in the eye and occasionally is treated with surgery.

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