A congenital cataract is an opacity of the lens of the eye that is present at birth or develops shortly after. It can be unilateral or bilateral. Some of the causes of congenital cataract include inherited disorders, metabolic diseases, infections, drug reactions and trauma. In most patients no cause can be find. Congenital cataracts are rare, but are one of the most common causes of visual impairment in children. The eye lens focuses light onto the retina, allowing a clear image to be formed. A cataract blocks the image that would normally reach the retina. During the first years of life, a clear image is required in order for the vision pathways in the brain to develop normally. Some congenital cataracts impair visual development only to a small degree and may never require surgery. If the cataract is larger, it can affect visual development in a significant way and in some cases can lead to an irreversible vision loss if not treated. In most cases, removal of the lens by surgery is the most effective treatment. Once the lens is removed, optical correction with a contact lens or glasses is usually necessary. Intraocular lenses are becoming more common in young children.