OBJECTIVE: To assess changes in pupil size and intraocular pressure (IOP) following topical application of a 0.5% tropicamide solution in the eyes of healthy butorphanol-sedated dogs. ANIMALS: 12 healthy adult Beagles. PROCEDURES: In a randomized crossover study consisting of 2 treatment periods with a 1-week washout between periods, dogs received an IM injection of butorphanol (0.2 mg/kg) or an equal volume of sterile saline (0.9% NaCl) solution. For each dog, 1 drop of 0.5% tropicamide ophthalmic solution was topically instilled in one eye and 1 drop of artificial tear solution was topically instilled in the other eye 10 minutes after the IM injection and again 5 minutes later. Extent of sedation, pupil size, and IOP were evaluated from 20 minutes before to 80 minutes after the IM injection and compared among treatment combinations. RESULTS: Butorphanol induced mild (n = 9) or moderate (3) sedation in all dogs and slightly delayed the onset of, but did not prevent, tropicamide-induced mydriasis. Butorphanol caused a significant increase in IOP, which was not exacerbated by tropicamide-induced mydriasis; however, that increase was generally not sufficient to exceed the upper limit of the IOP reference range. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that butorphanol did not prevent tropicamide-induced mydriasis but did increase the IOP in ophthalmologically normal Beagles. Although the butorphanol-induced increase in IOP did not appear clinically relevant for the dogs of this study, that may not be true for dogs with glaucoma, and care should be taken when butorphanol is administered to such dogs.

OBJECTIVE To determine the intraocular pressure (IOP) in healthy dromedary camels (Camelus dromedarius). ANIMALS 24 clinically normal dromedary camels. PROCEDURES For each camel, the IOP of both eyes was measured with applanation tonometry. Three measurements with < 5% variance were obtained for each eye on the same day of the week for 3 consecutive weeks. Mean IOP was calculated for each eye on each day for comparison purposes. RESULTS Mean ± SD IOPs for the right (31.1 ± 2.1 mm Hg) and left (30.8 ± 1.9 mm Hg) eyes of immature camels were significantly higher than those for the right (27.1 ± 1.2 mm Hg) and left (28.2 ± 1.2 mm Hg) eyes of mature camels. Intra-assay and interassay coefficients of variation (CVs) for IOP measurements of the right and left eyes did not differ significantly between immature and mature camels. Interassay CVs of IOP measurements for the right and left eyes ranged from 1.5% to 12.1% and 1.2% to 10.3%, respectively, for immature camels and from 1.2% to 17.2% and 1.7% to 18.8%, respectively, for mature camels. Intra-assay CVs of IOP measurements for the right and left eyes ranged from 1.5% to 10.6% and 1.9% to 9.6%, respectively, for immature camels and from 2.8% to 16.9% and 2.7% to 12.4%, respectively, for mature camels. Age was negatively correlated (r = −0.403) with IOP. CONCLUSIONS AND CLINICAL RELEVANCE Results provided a reference and might aid in the diagnosis of glaucoma and uveitis during complete ophthalmic examinations of dromedary camels.

The effects of mitomycin-C on intraocular pressure (IOP), facility of outflow (C), and Tenon's capsule fibrosis were studied over 60 days in 10 clinically normal dogs. A 1-piece, silicone glaucoma implant was surgically implanted into both eyes; the filtration site of one eye was treated with a single, 5-minute intraoperative application of mitomycin (0.5 mg/ml), and the fellow eye was treated in a similar manner with balanced salt solution. There were no significant differences in preoperative IOP or C-values between treatment groups. Mean IOP in eyes of both groups initially decreased from the preoperative value, but returned to the baseline value by day 21. Mean facility of aqueous outflow (C-value) increased in all eyes during the first 14 days (mitomycin-C-value = 2.26 +/- 0.72; control C-value = 2.38 +/- 0.81), then reached a plateau that was significantly higher than the baseline value in mitomycin (P = 0.039) and control (P = 0.041) eyes. Histologic evaluation revealed all implants surrounded by a connective tissue capsule composed of regular dense collagen and fibroblasts that was significantly (P = 0.003) thinner in the mitomycin-treated (scleral side = 167 +/- 62 micrometer; conjunctival side = 122 +/- 41 micrometer) than the control (scleral side = 261 +/- 92 micrometer; conjunctival side = 180 +/- 48 micrometer) group. There were, however, no significant differences in IOP or C-values between groups at any postoperative time interval. Results of this study indicate that intraoperative treatment with mitomycin suppresses, but does not prevent fibrosis around silicone filtering implants.

Ocular biometry, using A-scan ultrasonography and ultrasonographic pachymetry, was performed in 52 Samoyeds, 2 months to 13 years old, without intraocular or systemic diseases. Furthermore, the relative depth of the opening of the ciliary cleft was estimated from goniophotographs. The values were analyzed, and statistical models of changes in ocular distances with increasing age were identified. It was found that the changes in corneal thickness, axial anterior chamber depth, lens thickness, relative lens position, length of the vitreous body, and axial length could best be described by 1 of the 2 nonlinear models (...). The course began with a period of rapid increase, after which the ocular distance either increased at a progressively slower rate toward infinity (corneal and lens thickness) or to a finite limit (relative lens position and axial length), or ceased to grow and finally started to decrease toward minus infinity (axial anterior chamber depth and length of the vitreous body). However, suitable model for determining relative depth of the opening of the ciliary cleft could not be established. Results indicated that age-related changes, mainly in lens thickness, cause a shallow anterior chamber, and it was suggested that this may be of importance for development of a relative pupillary block and, thus, primary angle-closure glaucoma, at least in preconditioned eyes of Samoyeds.

The anterior chambers in 16 dogs with normotensive eyes and 3 Beagles with glaucomatous eyes were treated with 0, 25, 50, or 100 IU of bovine testicular hyaluronidase. Aqueous outflow resistance was then determined by constant-pressure perfusion of 0.9% NaCl solution for 30 or 60 minutes. In normotensive eyes, 25, 50, or 100 IU of hyaluronidase significantly (P < 0.02) increased the rate of constant-pressure perfusion compared with that of untreated eyes during 30- or 60-minute perfusions. Treatment of glaucomatous eyes with 25, 50, or 100 IU of hyaluronidase did not significantly increase the rate of constant-pressure perfusion over controls during a 30-minute perfusion. Bovine testicular hyaluronidase at all doses removed the staining of colloidal iron from the trabecular meshwork in normotensive eyes. In Beagles with glaucoma, the trabecular meshworks remained stained with colloidal iron when treated with the hyaluronidase, which suggested that some glycosaminoglycans were resistant to this enzyme's action.

Numbers of mast cells in the cornea, sclera, choroid, ciliary body, iris, and retina of sections of globes from 35 clinically normal dogs and 34 dogs with secondary glaucoma was determined. Fixed globes were trimmed along a vertical midsagittal plane and embedded in paraffin. Tissue sections, approximately 6 micrometer thick, were stained with toluidine blue for identification of mast cells. In normal globes, most of the mast cells were observed in the anterior portion of the uvea, and fewer mast cells were seen in the choroid and sclera. Mast cells were not observed in the retina and were seldom observed in the cornea of dogs with or without glaucoma. In sections of glaucomatous globes, mast cells were distributed evenly in the uvea and sclera, and fewer mast cells were present than in normal globes, regardless of the cause of glaucoma.

This study was aimed to evaluate the prophylactic anti-glaucoma effect of topical 5% betaxolol (BTX) and 2% dorzolamide (DRZ) on the second eye in dogs with unilateral primary angle closure glaucoma (PACG). Medical records of 60 dogs with unilateral PACG who received prophylactic anti-glaucoma eyedrops in the second eye, from 2016 to 2021, were reviewed. The prophylactic effects of BTX were maintained on 28/60 (46.7%) eyes until last visit and BTX failure was observed on median 510 (range, 53-1,927) days in 32/60 (53.3%) eyes. After DRZ instillation in BTX failure eyes, the prophylactic effects were extended at median 610 (range, 157-2,270) days in 21/32 (65.6%) eyes. DRZ failure eyes (17/21, 81.0%) eyes required chemical ablation or surgical intervention due to uncontrolled intraocular pressure. The duration of prophylactic effects was decreased with aging (R2 = 0.334, p = 0.006). The predominant breeds were Shih-Tzu (41.9%) and American Cocker Spaniel (30.6%) with no significant differences in survival curves (p = 0.210). The average prophylactic effects of BTX persisted more than 1.5 year and could be selected the first prophylactic eye drop in unilateral PACG. Also, early surgical intervention should be considered in prophylactic medications failure cases.

OBJECTIVE To evaluate the effectiveness of a novel fluorescence tracer agent, MB-102, for conducting ocular angiography in dogs. ANIMALS 10 ophthalmologically normal dogs (2 to 4 years old) and 10 dogs with retinal degeneration or primary open-angle glaucoma (< 6 years old). PROCEDURES While anesthetized, all dogs received sodium fluorescein (20 mg/kg, IV) or MB-102 (20 or 40 mg/kg, IV) first and then the other dye in a second treatment session 2 days later in a randomized crossover design. Anterior fluorescence angiography was performed on one eye and posterior fluorescence angiography on the other. Imaging was performed with a full-spectrum camera and camera adaptor system. Filter sets that were tailored to match the excitation and emission characteristics of each angiographic fluorescent agent were used. RESULTS All phases and phase intervals during anterior and posterior segment angiography were identified, regardless of the dye used. However, agent fluorescence and visualization of the iridal blood vessels were hindered in some dogs, irrespective of agent, owing to the degree of iridal pigmentation present. No significant difference was noted between the 2 dyes in any phase or phase interval, and slight improvement in image contrast was observed with MB-102 during the venous phases owing to a reduction of vessel wall staining in both normal and diseased eyes. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that MB-102 would be useful for conducting ocular angiography in dogs.

OBJECTIVE To determine whether 2- or 3-times-daily application of topical ophthalmic 0.005% latanoprost solution is more effective at lowering intraocular pressure (IOP) in clinically normal dogs. ANIMALS 9 clinically normal dogs. PROCEDURES For each dog, I drop of latanoprost 0.005% solution was applied to 1 eye every 8 or 12 hours each day for 5 days; the contralateral eye received topical ophthalmic treatment with 1 drop of saline (0.9% NaCl) solution at the times of latanoprost application. Ocular examinations of both eyes were performed every 6 hours starting 48 hours prior to and ending 42 hours after the treatment period. Following a 5-week washout interval, the procedures were repeated but the previously latanoprost-treated eye of each dog received latanoprost application at the alternate frequency. RESULTS Mean ± SD IOP reduction in the latanoprost-treated eyes was 31 ± 6.9% with 2-times-daily application and 33 ± 8.2% with 3-times-daily application. A 2-way repeated-measures ANOVA revealed significant differences in IOP with contributions by treatment (2 or 3 times daily), time of day (diurnal variation), and individual dog. The maximum mean daily IOP reduction in latanoprost-treated eyes was detected on day 3 of latanoprost treatment in each group. Eyes treated 3 times daily had significantly smaller pupil diameter and greater conjunctival hyperemia than eyes treated 2 times daily. CONCLUSIONS AND CLINICAL RELEVANCE The clinical importance of the ocular hypotensive effects of 3-times-daily topical ophthalmic application of 0.005% latanoprost solution in dogs with glaucoma warrants investigation.

Objective: To evaluate the effects of oral administration of diphenhydramine on pupil diameter, intraocular pressure (IOP), tear production, tear film quality, corneal sensitivity, and conjunctival goblet cell density (GCD) in clinically normal adult dogs. Animals: 12 healthy adult dogs. Procedures: All dogs received diphenhydramine (2.2 mg/kg, PO, q 12 h) for 21 days. Conjunctival biopsy samples were obtained immediately before (day 1) and after (day 21) treatment with diphenhydramine and conjunctival GCDs were determined. Gross ophthalmic examinations and fluorescein staining of corneas were performed, and pupil diameter, corneal sensitivity, IOP, tear production, and tear film breakup time were determined prior to administration of diphenhydramine on days 1 through 5 and on day 21; pupil diameter and IOP measurements were repeated on each of those days at 20 and 40 minutes and 1, 3, 6, and 8 hours after administration of diphenhydramine. Data were analyzed to detect differences among values for dogs. Results: Clinically important increases in pupil diameter were not detected after administration of diphenhydramine to dogs. Day 1 corneal sensitivity and tear film breakup time for dogs were significantly higher than day 21 values for those variables. Conclusions and Clinical Relevance: Results of this study suggested that oral administration of diphenhydramine to healthy adult dogs was not likely to acutely induce glaucoma or keratoconjunctivitis sicca. However, effects of diphenhydramine in dogs with keratoconjunctivitis sicca or primary glaucoma or dogs genetically predisposed to development of those conditions were not determined. Administration of diphenhydramine to dogs decreased corneal sensitivity and tear film breakup time, although these effects were not clinically important.