eye disorders
Cataract
Introduction
A cataract is a congenital or degenerative opacity of the lens. The main symptom is gradual, painless vision blurring. Diagnosis is by ophthalmoscopy and slit-lamp examination. Treatment is surgical removal and placement of an intraocular lens. Cataracts are the leading cause of blindness worldwide ( Reference ). In the United States, almost 20% of people aged 65 to 74 have cataracts that interfere with vision. Almost one in two people older than 75 has cataracts. Lens opacity can develop in several locations: Central lens nucleus (nuclear cataract) Beneath the posterior lens capsule (posterior subcapsular cataract) On the side of the lens (cortical cataract)—these usually do not interfere with central vision (For developmental or congenital cataracts, see Congenital Cataract .) 