Effects of twice daily application of 2% dorzolamide on intraocular pressure in normal cats

The effect of the topical carbonic anhydrase inhibitor, dorzolamide, on intraocular pressure in cats was studied. The intraocular pressure of both eyes of eight healthy cats was measured using applanation tonometery (Tono-Pen) during two phases: control and treatment. Both eyes were treated with 2% dorzolamide twice a day during the treatment phase. Application of dorzolamide resulted in a significant decrease of intraocular pressure over the treatment phase. By the fourth and fifth day of treatment, the mean intraocular pressure (+/- standard deviation) was 9.7 (+/- 1.5) mmHg, whereas the mean (+/- standard deviation) for the last 2 days of the control period was 12.2 (+/- 2.0) mmHg. Based on this study, dorzolamide is a potentially effective treatment for glaucoma in cats, significantly lowering intraocular pressure.     

Effect of topical 1% atropine sulfate on intraocular pressure in normal horses

OBJECTIVE: To determine the effect of topical 1% ophthalmic atropine sulfate on intraocular pressure (IOP) in ocular normotensive horses. Animals Studied Eleven clinically healthy horses. Procedures IOP was measured bilaterally twice daily, at 8 AM and 4 PM, for 5 days. No medication was applied for the first 2 days of the study. Thereafter, one eye of each horse was treated with 0.1 mL of topical 1% atropine sulfate ointment twice daily (7 AM and 7 PM) for 3 days. The contralateral eye served as a control. In eight of the horses, an additional IOP reading was taken 3 days following cessation of the atropine treatment. RESULTS: There was no significant difference in the IOP of control vs. treatment eyes in the pretreatment period, days 1 and 2 (P = 0.97 and 0.55, respectively). During the treatment period, treated eyes of 10 of the horses had significantly lower IOP than control eyes (P = 0.03). The mean IOP reduction in treated eyes, relative to untreated eyes, was 11.2%. One horse had a significant rise in IOP in the treated eye compared to the remaining study animals. The IOP of control eyes did not vary significantly over the observation period (P = 0.27). There was no significant variation in IOP between the 8 AM and 4 PM measurement (P = 0.9). CONCLUSIONS: Topical 1% atropine sulfate causes a small, but significant decline in IOP in most ocular normotensive horses. Because topical atropine may elevate IOP in some horses, it should be used with caution in the treatment of glaucoma in this species.     

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.     

Diode laser endoscopic cyclophotocoagulation in the normal equine eye

Objective To determine the clinical and histologic effects of diode endoscopic cyclophotocoagulation (ECP) in the phakic equine eye. Animals studied Phase I: 10 equine cadaver eyes. Phase II: four normal adult horses. Procedures Phase I: ECP probe angle of reach (AR) was determined. Multiple ECP energy levels: 0.75, 0.90, 1.05, 1.20, 1.35, 1.50 J, and the resulting visible and histologic ciliary process changes were evaluated. Phase II: Ocular quadrants were treated with ECP at 0.90, 1.14, 1.38 J, and a control. The contralateral eye underwent a sham operation. Tissue changes (clinical and histologic) were evaluated. Results Phase I: Mean combined AR was 162 ± 29 degrees. Mean visible tissue scores: 2.60 ± 0.58 (0.75 J) to 5.04 ± 0.30 (1.50 J) from possible total of 6. Tissue ‘popping’ was observed at 1.50 J. Histologic ciliary tissue damage was present at all settings. Phase II: Mean visible tissue scores: 2.90 ± 0.48 (0.90 J), 3.61 ± 0.57 (1.14 J), and 4.52 ± 0.56 (1.38 J). Tissue ‘popping’ was observed at 1.38 J. Histologic ciliary tissue damage was present at all settings. Clinical effects included acute inflammation, intraocular pressure reduction, cataract formation, corneal edema, corneal ulceration, and postoperative ocular hypertension. Conclusions Diode ECP between 0.90 and 1.14 J is a potential treatment option for glaucoma in horses based on visible tissue effects and target ciliary epithelium damage. Iatrogenic cataract development may limit the use of an anterior chamber approach in phakic horses. Supported in part by an ACVO VAF grant.     

Semiconductor diode laser transscleral cyclophotocoagulation for the treatment of glaucoma in horses: a retrospective study of 42 eyes

Objective To evaluate the outcome of diode laser transscleral cyclophotocoagulation (TSCP) for the treatment of glaucoma in horses. Procedure Medical records at The Ohio State University were reviewed. All horses that underwent diode laser TSCP between the years of 1995 and 2007 were included. Preoperative, procedural and clinical follow‐up data were collected, and telephone follow‐up was performed. Results Forty‐two eyes of 36 horses were included. Twenty‐four hours prior to surgery mean intraocular pressure (IOP) was 37.17 ± 13.48 mmHg (42 eyes). Forty‐one of 42 eyes (98%) were sighted and 39 of 39 (100%) of eyes were receiving topical glaucoma medication. At 3–5 weeks postoperatively the average IOP was 19.36 ± 12.04 mmHg (22 eyes). IOP remained significantly lower than pretreatment values at all periods of clinical follow‐up (P < 0.05). There was no significant difference in vision outcome, or the requirement for topical glaucoma medication relative to pretreatment values at any follow‐up period. Hyphema in 5 of 42 eyes was the only complication noted. Of the 27 eyes seen for clinical follow‐up, 2 were enucleated because of refractory elevation of IOP. Mean telephone follow‐up was 49 months. Twenty‐one of 22 owners contacted (95%) reported that the treatment had been of value, 14 of 22 eyes (64%) were receiving topical glaucoma medication, and 13 of 22 eyes (59%) were considered sighted. Conclusions Diode laser TSCP aided in the control of IOP and maintenance of vision but did not eliminate the need for topical glaucoma medication during the period of clinical follow‐up.