The lens inside the eye lies behind the colored iris and helps to focus light onto the retina. As the lens ages (or for certain other reasons), it becomes cloudy and cannot focus light very well. The term "cataract" is a general term describing such an opacity or cloudiness within the lens. The cloudy areas inside the natural lens block and scatter some of the light entering the eye, making the vision blurry and hazy. Thus, no matter what is done with glasses, the cataract still causes vision problems.
Cataracts typically occur in the ageing population, but may occur earlier in life. Factors such as family history, diabetes, long term UV exposure, trauma, or certain medications like steroids can also induce cataracts. Rarely, babies may be born with a cataract.
Generally, the ageing cataract changes so slowly that most patients adapt to blurred vision and are surprised by how well they can see after the cataract is repaired. Because an early cataract may change your glasses prescription (making the eye more nearsighted or causing astigmatism), some blur from cataract might be minimized by a change in glasses or contact lens prescription. However, once the cataract begins to interfere with a person's daily tasks despite the best corrective eyewear, surgery is the best option. Most cataracts do not actually harm the eye and do not need to be removed urgently; however, advanced cataracts may be more difficult to manage surgically, and certain cataracts may need to be removed for medical reasons other than causing blurred vision. Your doctor will carefully examine the eyes to make sure that there are no other conditions that are causing vision loss; it is important to understand that cataract surgery cannot fix vision lost by macular degeneration, glaucoma and other unrelated eye diseases.