Goniodysgenesis associated with primary glaucoma in an adult European Short-haired cat

Feline Glaucoma

Feline glaucoma is best categorized as either secondary, congenital and anterior segment dysgenesis associated, or primary. More than 90% of all feline glaucoma develops secondary to uveitis or intraocular neoplasia. The uveitis is usually idiopathic and assumed to be immune-mediated, whereas lymphosarcoma and diffuse iridal melanoma account for many of the intraocular neoplastic-induced glaucoma in cats. Several topical and systemic therapies are useful in the control of the inflammation and elevated intraocular pressures associated with feline glaucoma. Enucleation remains the recommended therapy for blind glaucomatous feline eyes. Enucleated globes from cats with chronic glaucoma should be submitted to an appropriate laboratory for histologic confirmation of the type of glaucoma.

Diagnostic Tests Used During the Ocular Examination

This article provides a review of the required ocular tests during the ophthalmologic examinations of canine and feline patients. Knowledge of medications affecting ocular parameters and awareness of available instrumentation and test materials is essential for accurate diagnoses.

The effect of dorzolamide 2% on circadian intraocular pressure in cats with primary congenital glaucoma

OBJECTIVE

To determine the extent of fluctuation in circadian intraocular pressure (IOP) and the efficacy of topical dorzolamide 2% q 8 h in lowering IOP and blunting circadian fluctuation in IOP in glaucomatous cats.

ANIMALS STUDIED

Seven adult cats with primary congenital glaucoma (PCG).

PROCEDURES

Measurements of IOP and pupil diameter were obtained for both eyes (OU) of each cat q 4 h for 12 days. Cats were housed in a laboratory animal facility with a 12-h light:dark cycle. Baseline values were established for 2 days. For the next 5 days, placebo (1.4% polyvinyl alcohol) was administered OU q 8 h. Dorzolamide 2% was then administered OU q 8 h for a further 5 days. A multivariate mixed linear model was fitted to the data, with parameters estimated from a Bayesian perspective. The 4 am time point was selected as the reference for the purposes of comparisons.

RESULTS

Estimated mean IOP for the reference time point pre-treatment was symmetric (about 33 mmHg OU). In all cats, IOP was significantly lower during the diurnal phase, relative to the 4 am measurements, with highest IOP observed 2-6 h after the onset of the dark phase. Circadian fluctuations in IOP were dampened during the treatment period. There was a significant decrease in IOP in all cats during the dorzolamide treatment period (estimated mean for the treatment period reference = 17.9 mmHg OU).

CONCLUSIONS

Topical dorzolamide 2% q 8 h is effective in reducing IOP and IOP fluctuation in cats with PCG.

Feline glaucoma--a comprehensive review

Cats with glaucoma typically present late in the course of disease. It is likely that glaucoma in cats is under-diagnosed due to its insidious onset and gradual progression, as well as limitations of some commonly used tonometers in this species. Treatment of glaucoma in feline patients presents a clinical challenge, particularly as glaucoma is often secondary to other disease processes in cats. In this review, we consider the clinical features, pathophysiology, and classification of the feline glaucomas and provide current evidence to direct selection of appropriate treatment strategies for feline glaucoma patients.