Anophthalmia and Retinal Degeneration Associated with Stenosis of the Optic Foramen in Fischer 344 Rats

Bilateral anophthalmia was discovered in a male rat (No. 1) and unilateral anophthalmia was found in the left eye of two female rats (Nos. 2 and 3) derived from a Fischer 344 inbred colony. One male rat (No. 4), a littermate of No. 3, had externally normal eyes, but his left eye had severe retinal atrophy, which was detected by ophthalmoscopy. The eyelids in both eyes of No. 1 and in the left eyes of Nos. 2 and 3 were present. Radiography of the skull revealed small optic foramina on both sides of No. 1 and on the affected side of Nos. 2, 3, and 4. Histologically, both globes and optic nerves (ONs) of No. 1 and the left globe and ONs of Nos. 2 and 3 were completely missing. Diffuse retinal degeneration in the left globe and axonal degeneration in the left ON and the right optic tract were observed in No. 4. Dysplasia of the sphenoid bone associated with stenosis of the optic foramen was detected on the affected side of all rats. Thus, ON aplasia in anophthalmic rats and atrophic ON in a rat with retinal degeneration seem to be closely related to stenosis of the optic foramen.