This report presents a study of cataracts seen in a random-bred strain of Swiss mice with Balb/c mice used as a control group. The embryonic development, and histological and slit lamp observations of the lenses in the two groups, of animals are contrasted.
The cataract is dominant in its inheritance (Tissot, '62). It appears either unilaterally or bilaterally as a dense white opacity in the lens substance. The earliest sign of abnormal formation occurs at 14 days of embryonic development. This is associated with a defect in the primary lens fibers formation. Progressive degeneration of these fibers occurs until they are reduced to a mass of cellular debris seen at the last day of gestation. The secondary fibers are also laid down in a n abnormal manner. The normal lamellar arrangement of the secondary fibers is not seen in cataractous lenses.
The abnormal lens fiber development leads to progressive vacuolization. The mature cataract seen in the adult is filled with many vacuoles, the largest ones occurring at the equatorial region. The nuclear region consists of a clumpy eosinophilic mass with scattered calcified areas. The rate of growth of the secondary fibers is different from that of the normal group. Most of the mature cataracts in the adult contain a vascularized epithelium.
There are three possible areas of primary involvement which may lead to the development of the cataract. This are: (1) A defect in the development of the primary lens fibers;
( 2 ) A defect in the development of the secondary lens fibers; (3) A n abnormal lens epithelium which may interfere with nutrition of the lens and thus initiate cataract formation.
LITERATURE CITED Bard, P. 1961 Medical Physiology. The C. V.