Unilateral lens capsule rupture with anterior nuclear extrusion in a North American river otter (Lontra canadensis).

Abstract

A 10-year-old intact male North American river otter (Lontra canadensis) was evaluated under general anesthesia by a zoo veterinarian and 2 Board-certified ophthalmologists concerning a white opacity in the anterior chamber of the right eye (OD). Ophthalmic examination of OD revealed ventral keratitis, a hypermature cataract, equatorial lens capsule rupture, and anterior luxation of the lens nucleus. The right eye lacked a dazzle, direct, and indirect pupillary reflexes. No ocular anomalies were noted in the left eye. Enucleation of OD was conducted due to vision loss, the anticipation of constant need for medication to control uveitis, and the increased risk for secondary glaucoma. Histologic examination of OD confirmed a cataract, phacolytic uveitis, and lens epithelium migration and proliferation, consistent with lens capsule rupture. The extrusion of the cataractous nucleus could have been due to the powerful ciliary body muscles in otters. The contraction of these muscles may have increased the curvature of the anterior portion of the lens, causing the weakened lens capsule to rupture and extrude the nucleus into the anterior chamber.