Corneal diagnostic procedures.

The cornea is the anterior, transparent portion of the fibrous tunic of the eye. It is continuous with the sclera at a transition called the limbus. In healthy conditions, the transparency of the cornea is maintained by the smooth, nonkeratinized, squamous epithelium, which is further enhanced by the precorneal tear film, the lack of corneal vascularization or pigmentation, the size and regular arrangement of the collagen fibrils that make up the corneal stroma, and the relative dehydration of the cornea (which is maintained by the endothelium and epithelium). The cornea can respond to adverse stimuli through vascularization, pigmentation, fibrosis, accumulation of cellular or noncellular infiltrate, and/or edema. Because of these limited responses, routine diagnostic procedures are critical in the diagnosis and treatment of corneal disorders. This article discusses tests of the precorneal tear film, corneal staining procedures, culture and sensitivity, cytology, and a few other procedures that are performed less commonly or require specialized instrumentation.

Histologic effect of semiconductor diode laser transscleral cyclophotocoagulation on the normal equine eye.

OBJECTIVE: To determine the acute histologic effects of semiconductor diode laser transscleral cyclophotocoagulation (TSCP) on the normal equine eye. ANIMAL STUDIED: Part 1: eight eyes of four horses. Part 2: 10 eyes of five horses. MATERIALS AND METHODS: Part 1: TSCP was performed on four eyes at 4 mm and four eyes at 6 mm posterior to the limbus with 15 sites treated in four quadrants at 1800 mW for 1500 ms. The globes were sectioned transversely or sagitally to examine all quadrants and histologic sections were taken every 1 mm for the entire globe. Part 2: Based on the results from Part 1, TSCP was performed at 20 sites 4 mm posterior to the dorsotemporal limbus with a constant energy varying from 0.75 to 4 J/site. Histologic sections were taken every 1 mm for a total of 10 sections per eye and 20 sections per energy level group. RESULTS: Part 1: At 4 mm posterior to the limbus, coagulation of the nonpigmented epithelium (NPE) of the pars plicata was observed in the temporal (14%) and dorsal quadrants (12%). Retinal detachment was observed in the nasal quadrant (12%). Hemorrhage was common in the nasal (19%) and temporal (12%) quadrants. At 6 mm posterior to the limbus, coagulation of the NPE of the pars plicata was observed in the dorsal (14%), ventral (16%), nasal (2%), and temporal (2%) quadrants. Retinal detachment was observed in the dorsal (8%), ventral (18%), nasal (20%) and temporal (2%) quadrants. Part 2: Settings of 0.75 J/site were ineffective; 1.5, 2.25 and 3 J/site damaged the pars plicata without disruption of anatomy; and 4 J/site caused disruption of normal architecture. CONCLUSIONS: The most appropriate site for equine TSCP appears to be 4 mm posterior to the dorso- and ventrotemporal limbus avoiding the 3 and 9 o'clock positions and using an initial energy setting of 2.25 J/site. This results in effective damage to the pars plicata while minimizing surgical complications such as retinal detachment and hemorrhage.

Unilateral exophthalmia in a European hedgehog (Erinaceus europaeus) caused by a lacrimal ductal carcinoma.

A 5-year-old European hedgehog was examined because of exophthalmos of the left eye. A retrobulbar mass in the ventromedial orbit was suspected and confirmed by a computed tomography scan. Exophthalmos progressed despite systemic broad-spectrum antibiotic therapy. The left orbit was exenterated and the mass was partially removed. The histopathologic diagnosis was lacrimal ductal carcinoma. Lacrimal ductal carcinoma is rare in humans and animals. The long-term prognosis is guarded to poor.