Microphthalmia with multiple ocular abnormalities in a foal

Objective: The aim of this report was to provide a clinical description and clinical, ultrasonographic, and histologic images of a foal with microphthalmia and multiple ocular abnormalities.

Animals studied: A 12-h old Friesian-American Paint Horse crossbred filly presented for blindness, microphthalmia and marked ventral strabismus in both eyes.

Procedure: A complete ophthalmic examination was performed. Ultrasound biomicroscopy and B-mode ultrasonography were performed. The globes were submitted for histopathology.

Results: Ultrasound biomicroscopy demonstrated a hyperechoic cornea void of the typical epithelium, stroma, and Descemet's membrane layers. The anterior chamber was spanned by thick strands of hyperechoic tissue extending from the iris to the cornea. The lens was not visualized. B-mode ultrasound showed aphakia and mild, mottled echogenicity within the vitreous with no evidence of retinal detachment. On histopathology, both globes were microphthalmic with poorly defined corneal tissue. The anterior chambers were poorly formed and contained lacrimal glandular tissue. Portions of iridal tissue were present, but no lenses were noted. The retinas were segmentally detached and markedly atrophied with areas of retina dysplasia noted.

Conclusions: This report provides a clinical, ultrasonographic and histologic description of a rare, congenital condition in a foal characterized by microphthalmia, aphakia, poorly defined corneal tissue, choristomatous differentiation of the anterior segment and retinal dysplasia.