Diagnostic Ophthalmology

A 10-year-old spayed female domestic shorthaired cat was examined at the ophthalmology serviceat the Western College of Veterinary Medicine. This cat was presented for evaluation of pigmented lesions in the left iris. The menace responses, and palpebral, occulocephalic, direct and consensual pupillary light reflexes were present bilaterally. Schirmer tear test (Schirmer Tear Test Strips; Alcon Canada, Mississauga, Ontario) values were 16 and 21 mm/min in the right and left eyes, respectively. The intraocular pressures were estimated with a rebound tonometer (Tonvet; Tiolat, Helsinki, Finland) and were 13 and 25 mmHg in the right and left eyes, respectively. Fluorescein staining (Fluorets; Bausch & Lomb Canada, Markham, Ontario) was negative bilaterally. On direct examination there was brown discoloration of the left iris extending approximately 300° and mainly involving the peripheral iris. Biomicroscopic examination (Osram 64222; Carl Zeiss Canada, Don Mills, Ontario) revealed the darkly pigmented areas to be flat and the pigmentation to extend into the iridocorneal angle involving the pectinate ligaments. Examination of the right eye was within normal limits. Following topical application of 0.5% tropicamide (Mydriacyl; Alcon Canada, Mississauga, Ontario) indirect ophthalmoscopic (Heine Omega 200; Heine Instruments Canada, Kitchener, Ontario) examination was completed and did not identify abnormalities in either eye. A photograph of the left eye at presentation is provided for your assessment (Figure 1)