A cataract is a clouding of the lens of the eye, caused by proteins on the surface. Under normal circumstances, the proteins in the lens allow light to pass through. As we age, the proteins clump together and cloud an area of the lens. Damage and injury can also cause the lens to cloud. There are three different types of cataracts, based on their location and how they affect the lens. A subcapsular cataract begins on the back of the lens and is common in people with diabetes, retinitis pigmentosa and those taking steroids. A nuclear cataract forms in the nucleus of the lens and is most common in the elderly. A cortical cataract occurs in the outer covering of the lens and gradually extends toward the center. Cortical cataracts are also common in diabetics.
Early Symptoms
Cataracts are painless and develop slowly, over time. Initially, the cloudiness may affect a small part of the lens and the patient may not notice any vision loss. Other patients may notice slightly blurred vision and sensitivity to sunlight. Colors may appear dimmed and the patient may notice halos around lights.
Later Symptoms
As the cataract grows larger, it clouds more of the lens and the vision loss is more noticeable. The patient may experience double vision in one eye and greater sensitivity to light. The clouding, from cataracts, affects night vision by blocking available light and creating a glare around supplemental lights, like headlights. Nuclear cataracts are unusual in that they cause a temporary improvement in vision, known as "second sight." The improvement is temporary and the vision worsens as the cataract grows. On the other hand, subcapsular cataracts have no initial symptoms at all, until they are severe enough to cause serious vision problems.
Other Symptoms
As stated before, cataracts are painless. If the patient experiences burning, itching and inflammation, in conjunction with clouding of the eye, it is most likely due to a condition other than cataracts. The only exception is with hypermature cataracts, where the cataract becomes completely white and completely obstructs vision. In those cases there may be pain and inflammation of the eye, as well as headache.
