The explanation of such abnormalities as the following is undoubtedly to be found in interference with complete closure of the fetal ocular cleft, located at the lower side of the secondary ocular vesicle, and designed for admission of the mesoderm. There is no agreement of opinion as to the cause of the interference with the normal closure of this cleft. By some it is attributed to abnormal persistence of the mesodermic tissue; by others, to fetal inflammation in the region of the cleft. The influence of heredity has also been noted. Lang and Collins prefer to ascribe the defect in chorioidal coloboma to an abnormal adhesion of the retina to the mesoblast. When this occurs before the retinal fissure closes, the coloboma is devoid of retinal elements; but when it occurs later, the retina is present and there is no scotoma corresponding to the colobomatous area.
In some cases of
PYLE WL. MICROPHTHALMUSWITH EXTENSIVE COLOBOMATA AND OTHER CONGENITAL DEFECTS IN BOTH EYES.. JAMA. 1908;L(10):765–766. doi:10.1001/jama.1908.25310360027002a