A cataract is present when the transparency of the lens is reduced to the point that the patient’s vision is impaired. The term cataract comes from the Greek word katarraktes (downrushing; waterfall) because earlier it was thought that the cataract was a congealed fluid from the brain that had flowed in front of the lens.
Development of the cataract and its symptoms is gen-erally an occult process. Patients experience the various symptoms such as seeing only shades of gray, visual impairment, blurred vision, distorted vision, glare or star bursts, monocular diplopia, altered color perception, etc. to varying degrees, and these symptoms will vary with the specific type of cataract (see Table 7.3 and Figs. 7.7a and b).
Diagnosis of a cataract is generally very unsettling for patients, who immediately associate it with surgery. One should therefore refer only to a cataract when it has been established that surgery is indicated. If the cataract has not progressed to an advanced stage or the patient can cope well with the visual impairment, one should refer instead to a “lens opacity.”
Cataracts may be classified according to several different cri-teria.
❖ Time of occurrence (acquired or congenital cataracts).❖ Maturity.
No one classification system is completely satisfactory. We prefer the system in Table 7.1.