A cataract means a cloudy or opacified lens. The lens is the middle window which separates the front (anterior) and back (posterior) segments of the eye. In a normal eye, it focuses the image entering the eye onto the retina. The retina is the innermost layer of the eye which converts the images into biochemical signals which are subsequently transmitted to the brain.
As you age, your lens becomes gradually more opaque. This affects the amount of light that enters the eye and the ability for images to be focused onto the retina. Your eyesight gradually becomes more blurry and your visual acuity decreases. The more severe the lens opacity, the less light enters the eye and the less the eye sees. Another disabling effect is glare, especially at night. An increase in myopia may occur when the lens becomes denser and thicker. Sometimes, it may also cause the perception of double vision even with the other eye closed.
Unfortunately, age is the most common culprit. This means that your lens will gradually become cloudy as you grow older, despite how much you may want to protest against it. As you age, the lens tissues no longer function as efficiently, leading to buildup of oxidants and insoluble proteins in the lens. The combination of oxidation damage and protein accumulation is thought to cause the lens to become cloudy and opaque.
Aging is not the only cause of lens opacities. You can be born with congenital cataract. It can also occur with other eye diseases or general health conditions. Associated eye diseases include acute angle closure glaucoma, keratoconus, and uveitis. General health conditions linked with lens clouding include diabetes mellitus, high blood pressure and genetic conditions such as Down syndrome.
Essentially, anything that can disrupt the local lens environment will likely cause the lens to become hazy. Eye surgery, such as glaucoma surgery and retinal detachment surgery, usually results in cataract development within 1 to 2 years. Steroids (even in creams, inhalers and nasal sprays) and contraceptive pills are also associated with opacification of the lens.
There are various types of lens opacities depending on how they look on examination. However, the principle for the treatment of all types is the same. There may be slight differences in technique, but these are minor and do not affect the outcome of surgery.