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Topical 1, 2, and 4 percent pilocarpine were evaluated in the normotensive and glaucomatous beagles, comparing intraocular pressure (IOP), pupillary size, and time. In normotensive beagles pilocarpine produced maximal decreases of 25 percent (5.5 mm. Hg) at 1 percent concentration; 34 percent (7.26 mm. Hg) at 2 percent concentration; and 25 percent (6.9 mm. Hg) at 4 percent concentration. The maximum reductions in IOP after pilocarpine instillation in the glaucomatous beagle were 30 percent (9.1 mm. Hg) at 1 percent concentration; 44 percent (14.92 mm. Hg) at 2 percent concentration; and 31 percent (10.89 mm. Hg) at 4 percent concentration. The glaucomatous beagles responded with a greater reduction of IOP than did the normotensive beagles.

Fifty-nine normal dogs, ranging in age from 6 weeks to 132 months were examined with contact specular microscopy to determine the relationship of age to corneal endothelial cell density, morphology, and corneal thickness. Canine corneal endothelial cells appear quite similar to those of other species studied, including man. The hexagonally shaped canine endothelial cells tend to enlarge with age, with the population in young animals averaging around 2500 cells/mm2 and the number of cells in older dogs being frequently below 2100 cells/mm2. A significant increase in corneal thickness was observed with age. Healthy canine corneal endothelial cells appear to maintain a functional monolayer by enlargement and migration and represent a reasonable model for future endothelial cell study.

Twenty-one dogs were used to study the effects of phacoemulsification and extracapsular lens removal on corneal endothelium and corneal thickness. Specular microscopy revealed preoperative cell morphology and cell densities similar to man. After surgery endothelial cell counts significantly decreased 22% (central) and 13% (periphery) with phacoemulsification and 34% (central) and 31% (periphery) with extracapsular lens removal. Corneal thickness increased with both procedures. Endothelial cell pathology included cellular enlargement, increased pleomorphism, and focal cellular degeneration. Phacoemulsification time did not correlate with the degree of cell loss. Dog corneal endothelium responds to surgical trauma in a manner similar to man and maintains a functional monolayer via cellular enlargement and migration. The dog, therefore, represents a good animal model for the study of corneal endothelial disease in man.

Inherited glaucoma was exhibited in 55 beagles. The glaucomatous process was divided into early (6 to 12 months of age), moderate (13 to 30 months of age), and advanced (31 months of age). In early glaucoma the tridocorneal angles, as judged by gonioscopy, were open and without anomalies, intraocular pressure was elevated, and the tonographic facility of aqueous outflow was decreased. With moderate glaucoma, the tridocorneal angles were typically open; intraocular pressure was elevated, facility of aqueous outflow was decreased; and variable optic disc cupping and focal disinsertion of the zonules from the lens were seen. Advanced glaucoma exhibited narrow to closed tridocorneal angles, decreased facility of aqueous outflow, elevated intraocular pressure, lens dislocation, optic disc atrophy, and finally phthisis bulbi. The beagle in the early and moderate stages of glaucoma, before angle closure and lens dislocation, is an animal model for studies in open-angle glaucoma.

The Mackay-Marg, pneumatonograph, TonAir, and EMT-20 tonometers were evaluated in the normal dog eye. Tonometric scale readings were compared to the manometric recordings from the anterior chamber. The Mackay-Marg tonometer evaluated in open and closed systems was the most reliable (goodness of fit [r2] = 0.96) with intraocular pressure up to 100 mm. Hg. The pneumatonograph also exhibited high reliability (r2 = 0.92) but tended to underestimate intraocular pressures above 40 to 50 mm. Hg. The TonAir and EMT-20 tonometers were the least satisfactory for the dog, with r2 of 0.77 and 0.66 to 0.81, respectively. The Mackay-Marg is the most satisfactory tonometer for the dog.