How does a cataract affect vision?

A cataract acts like a filter that reduces the amount of light that reaches the retina, the light-sensitive tissue at the back of the eye. Common symptoms include colors appearing dull, general blurring, and glare, particularly with night driving. Cataracts may also cause a change in prescription, typically an increase in nearsightedness and astigmatism. In fact, a lens update may be all that is necessary to address an early cataract.