Cataract is caused by the opacification and degeneration of the lens fibres in the eye. Symptoms include blurred vision, problems with glare when driving at night, and changes in color vision. Cataracts are classified based on their morphology, age of onset, maturity, and etiology. Some of the main types include nuclear, cortical, and posterior subcapsular cataracts. Cataracts are also classified as congenital, juvenile, pre-senile, or senile depending on the age at which they develop.