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. 18-10). In

Posterior Capsule Cataract



Artificial lens implanted in posterior capsule

What Posterior Cataract

Artificial lens implanted in anterior chamber

FIGURE 18-10. 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.

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.

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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