Cataract Definition

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.

General symptoms: Development of the cataract and its symptoms is generally 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. 7.7 a and b).

H 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 orthe patient can cope well with the visual impairment, one should refer instead to a "lens opacity."

Cataract symptoms.

Cataract symptoms.

Fig. 7.7 a Visual image without a cataract.

b Visual image with a cataract: gray areas and partial loss of image perception.

Fig. 7.7 a Visual image without a cataract.

b Visual image with a cataract: gray areas and partial loss of image perception.

Classification: Cataracts may be classified according to several different criteria.

❖ Time of occurrence (acquired or congenital cataracts).

No one classification system is completely satisfactory. We prefer the system in Table 7.1.

Table 7.1 Classification of cataracts according to time of occurrence

Acquired cataracts

Senile cataract (over 90% of all cataracts)

(over 99% of all cataracts)

Cataract with systemic disease

- Diabetes mellitus

- Galactosemia

- Renal insufficiency

- Mannosidosis

- Fabry's disease

- Lowe's syndrome

- Wilson's disease

- Myotonic dystrophy

- Tetany

- Skin disorders

Secondary and complicated cataracts

- Cataract with heterochromia

- Cataract with chronic iridocyclitis

- Cataract with retinal vasculitis

- Cataract with retinitis pigmentosa

Postoperative cataracts

- Most frequently following vitrectomy and

silicone oil retinal tamponade

- Following filtering operations

Traumatic cataracts

- Contusion or perforation rosette

- Infrared radiation (glassblower's cataract)

- Electrical injury

- Ionizing radiation

Toxic cataract

- Corticosteroid-induced cataract (most

frequent)

- Less frequently from chlorpromazine, miotic

agents, or busulfan

Congenital cataracts

Hereditary cataracts

(less than 1 % of all cataracts)

- Autosomal dominant

- Recessive

- Sporadic

- X-linked

Cataracts due to early embryonic (trans-

placental) damage

- Rubella (40-60%)

- Mumps (10-22%)

- Hepatitis (16%)

- Toxoplasmosis (5%)

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