Congenital cataracts cause 10 to 30% of all blindness in children, with one-third of cases estimated to have a genetic cause (summary by Bu et al., 2002). Mutations in the HSF4 gene have been found to cause multiple types of cataract, which have been described as infantile, lamellar, zonular, nuclear, anterior polar, stellate, and Marner-type. The preferred title for this entry was formerly 'Lamellar Cataract,' with 'Cataract, Marner Type; CAM; CTM' an included title.

A congenital abnormality of the cornea in which the cornea and the anterior segment of the eye are smaller than normal. The horizontal diameter of the cornea does not reach 10 mm even in adulthood.

A nuclear cataract is an opacity or clouding that develops in the lens nucleus. That is, a nuclear cataract is one that is located in the center of the lens. The nucleus tends to darken changing from clear to yellow and sometimes brown.