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SUMMARY

Objective

To compare in vitro opening pressures (OP) and closing pressures (CP) of the Ahmed VS-1 and VS-2 glaucoma valves with those of several selfconstructed valve ‘prototypes,’ and to assess their ability to maintain perfusion pressures between 6 and 21 mm of Hg.

Sample Population

Ahmed VS-1 (n = 6), 2 groups of Ahmed VS-2 (group 1: n = 12; group 2: n = 14), and self-constructed valves with linear incisions in the long axis of the tube wall (n = 6) or X-shaped incisions in the tube walls (n = 2).

Procedure

Valves were perfused with deionized water, lactated Ringer's solution (LRS), Dulbecco's modified Eagle's medium (DMEM), DMEM plus 50% equine serum (ES), and 100% ES. Flow rates of 2.85, 4.2, 6.0, 9.0, and 12.0 μl/min were used for each perfusate. Valves were tested 3 times for reproducibility, and OP/CP were compared for each system.

Results

OP/CP of the VS-1, VS-2 (group 1), VS-2 (group 2), and linear 1.0-cm incisional valves with thick tubing consistently increased with increasing perfusion rate. Linear 0.5-cm (thick tubing) and 1.0-cm (thin tubing) incisional valves had increasing OP/CP with increasing perfusion rate in all but a few instances. Mean OP/CP decreased with increasing perfusate osmolarity for all perfusates except LRS, using the VS-1 and V-2 (group 2) valves. Mean OP/CP were consistently lower for VS-1 than VS-2 (group 1) valves at any given flow rate and for any given perfusate. Mean OP/CP were consistently lower for VS-2 (group 1) than VS-2 (group 2) valves at any given flow rate and for any given perfusate. The linear 0.5-cm incisional valves with thick and thin tubing induced the highest mean OP/CP, maximizing at > 30 mm of Hg.

Conclusions

Only the VS-2 (group 2) valves consistently had mean OP/CP between 6 and 21 mm of Hg for all perfusates and at all flow rates.

Clinical Relevance

Anterior chamber shunts, although imperfect, appear to offer a physiologically sound alternative for glaucoma management. (Am J Vet Res 1997;58:1332–1337)

Free access
in American Journal of Veterinary Research

SUMMARY

Topically applied 4% timolol, 4% timolol combined with 2% pilocarpine, 6% timolol, and 6% timolol combined with 2% pilocarpine were evaluated in clinically normal Beagles and Beagles with glaucoma. The drugs were instilled twice daily for 5 days. Changes in intraocular pressure (iop), pupil size, and heart rate were recorded on days 1, 3, and 5 at 0, 2, 5, and 8 hours, starting at 8:30 am. In clinically normal dogs, 4 and 6% topically administered timolol did not cause consistent reductions in iop; however, with addition of 2% pilocarpine, iop was consistently lower. In the Beagles with glaucoma, 4 and 6% timolol and, to a greater extent, 4 and 6% timolol combined with 2% pilocarpine lowered iop. The combinations lowered iop and reduced pupil size consistently. In all test groups, either 4 or 6% topically applied timolol caused approximately 10% decrease in mean heart rate.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To examine postoperative ocular hypertension (POH) and other variables as predictors of the risk of developing glaucoma after cataract surgery in dogs.

Design—Retrospective study.

Animals—220 dogs that had cataract surgery.

Procedure—Medical records of 220 dogs (346 eyes) that had extracapsular cataract removal or phacoemulsification of cataracts were reviewed. With respect to glaucoma development, 8 variables were analyzed, which included development of POH, breed, sex, age at time of surgery, eye (right vs left), phacoemulsification time, intraocular lens (IOL) placement (yes or no), and stage of cataract development. Eyes developed glaucoma within 6 or 12 months of surgery or did not have signs of glaucoma at least 6 or 12 months after cataract surgery.

Results—Of 346 eyes, 58 (16.8%) developed glaucoma after surgery. At 6 months, 32 of 206 (15.5%) eyes examined had glaucoma; at 12 months, 44 of 153 (28.8%) eyes examined had glaucoma. Median follow-up time was 5.8 months (range, 0.1 to 48 months). Mixed-breed dogs were at a significantly lower risk for glaucoma, compared with other breeds. Eyes with IOL placement were at a significantly lower risk for glaucoma, compared with eyes without IOL placement. Eyes with hypermature cataracts were at a significantly higher risk for glaucoma, compared with eyes with mature or immature cataracts.

Conclusions and Clinical Relevance—Multiple factors appear to contribute to the onset of glaucoma in dogs after cataract surgery. Complications prohibiting IOL placement during cataract surgery may lead to a high risk of glaucoma development. (J Am Vet Med Assoc 2000;216:1780–1786)

Full access
in Journal of the American Veterinary Medical Association