Mature cataract due to eczema affecting a person's right eye. Cataract is a general term that describes the denaturation of proteins in the eye's lens that produces an opacity which may vary in severity from insignificance to severe loss of sight. This mature cataract appears as a light blue opaque mass behind the iris. Cataracts caused by disease (as in this case due to severe eczema) are relatively rare. The most common cause is ageing, with the cataract developing over a number of years. Congenital cataracts are rare. Surgery is the only effective form of treatment.