Unilateral Colobomata Nervus Opticus in Young Slc: Wistar Rats

Abstract

Unilateral colobomata nervus opticus was observed in two 6-week-old Slc: Wistar rats. A fixed pupil was found in one rat, and aplasia of the optic disk and the central retinal arteries and veins was detected in both animals. At necropsy, the left optic nerve was completely absent from the posterior pole of the eye to the optic chiasma, and the right optic tract was barely visible in both rats. The eyes appeared normal in size.

Histologically aplasia of the optic disk, retinal atrophy, rosette formation of the retina, and hypoplasia of the ciliary body were observed in both cases.

One of the rats had subretinal hemorrhage and nodular hyperplasia of connective tissues in the choroid. The inner layer of the retina was markedly atrophied, resulting in a definite decrease in the ratio of brain layer to whole layer of the retina.

Although the right optic tract was markedly reduced in volume, there were neither degenerative changes nor inflammatory reaction in the tract. The two cases were histopathologically diagnosed as congenital unilateral aplasia of the optic nerve, accompanied by hypoplasia of the retina.