Cataract: Types and Symptoms

Cataract means the opacity of the eye lens or its capsule. It is the single largest cause of blindness all over the world. Cataracts are usually bilateral, though unilateral cases also occur. The cause is generally hereditary but other unidentified factors may also be the reason for its development.

There are a variety of types of cataracts that may develop.

According to Causes:

Congenital (or Developmental) cataract occurs at the time of birth and rarely interferes with the vision. Senile type occurs in old age and is the commonest variety of cataract. Most of the people over the age of 60 years have some degree of lens opacity. The toxic type occurs after the administration of drugs such as steroids.

Systemic disease associated cataract occurs with some systemic disease such as atopic dermatitis whereas Metabolic cataract occurs with diseases such as diabetes, hypocalcemia, galactosemia or Wilson’s disease.

Secondary cataract is a complicated condition, which occurs secondary to certain eye diseases like uveitis or occult tumour (retinoblastoma). Traumatic cataract occurs after trauma such as heat, electric shock, radiation or perforation.

According to Stage of Progression:

In immature cataract, some transparent fibres are still present and the vision gets reduced. In intumescent variety, the lens swells up due to the collection of fluid between the lens fibres.

In mature cataract, the entire lens becomes opaque whereas in hyper-mature variety of cataract, the lens protein leaks out followed by fluid secretion, thereby leading to the shrinkage of the lens.

According to Morphology:

As per the part involved, the cataract can be capsular, sub-capsular, cortical, supra nuclear, nuclear or zonular.

Symptoms of Cataract

The symptoms are slowly progressive and depend upon the location and density of lens opacity. These include visual loss (over months or years) without pain or redness, vision blurs at distance more than near, reading difficulty in people over 50 years of age, glare while driving at night and reduced colour perception.