Effect of three treatment protocols on acute ocular hypertension after phacoemulsification and aspiration of cataracts in dogs

Objective  To compare the effect of topical latanoprost, intracameral carbachol, or no adjunctive medical therapy on the development of acute postoperative hypertension (POH) and inflammation after routine phacoemulsification and aspiration (PA) of cataracts in dogs.
Design  Retrospective study.
Procedures  Dogs received either one drop of topical 0.005% latanoprost (21 dogs, 39 eyes), an intracameral injection of 0.3 mL of 0.01% carbachol (15 dogs, 30 eyes), or no adjunctive therapy (46 dogs, 90 eyes) immediately following PA of cataract(s). Intraocular pressure (IOP) was measured in all dogs 2 and 4 h after surgery. IOP was measured and aqueous flare assessed at 8 am the day after surgery.
Results  Carbachol-treated dogs had significantly higher mean IOP (33.2 ± SD 20.8 mmHg) 2 h after surgery than dogs receiving no adjunctive therapy (22.0 ± SD 14.1 mmHg) ( P  =  0 .049). There were no significant differences in IOP among groups at any other time point. There were no significant differences in number of POH episodes between dogs treated with carbachol (47%), latanoprost (29%), or dogs that received no adjunctive therapy (33%). There were no significant differences in mean aqueous flare grade between eyes treated with latanoprost (1.7 ± SD 0.4) or carbachol (1.4 ± SD 0.6), and eyes that received no adjunctive therapy (1.7 ± SD 0.4).
Conclusions  Topical 0.005% latanoprost or intracameral injection of 0.3 mL of 0.01% carbachol after PA in dogs did not reduce POH or increase intraocular inflammation compared to dogs not receiving adjunctive therapy after PA of cataracts.     

The effect of a single dose of topical 0.005% latanoprost and 2% dorzolamide/0.5% timolol combination on the blood-aqueous barrier in dogs: a pilot study

Objective To determine the effects of 0.005% latanoprost and 2% dorzolamide/0.5% timolol on the blood‐aqueous barrier (BAB) in normal dogs. Animals studied Eight mixed‐breed and pure‐breed dogs. Procedures Baseline anterior chamber fluorophotometry was performed on eight normal dogs. Sodium fluorescein was injected and the dogs were scanned 60–90 min post‐injection. Seventy‐two hours following the baseline scan, one eye received one drop of latanoprost. Fluorophotometry was repeated 4 h after drug administration. Following a washout period, the identical procedure was performed 4 h after the administration of dorzolamide/timolol. The degree of BAB breakdown was determined by comparing the concentrations of fluorescein within the anterior chamber before and after drug administration. BAB breakdown was expressed as a percentage increase in the post‐treatment fluorescein concentration over the baseline concentration: %INC [Fl] = {([Fl]_post – [Fl]_baseline)/[Fl]_baseline} × 100. The percentage increase in fluorescein concentration in the treated eye was compared to that in the nontreated eye using a paired t‐test with significance set at P ≤ 0.05. Results Following administration of latanoprost, the fluorescein in the treated eyes increased 49% (± 58%) from baseline compared to 10% (± 31%) in the untreated eyes (P = 0.016). Following administration of dorzolamide/timolol, the fluorescein concentration increased 38% (± 54%) compared to baseline vs. 24% (± 38%) in the untreated eyes (P = 0.22). Conclusions The results of this study show that topical latanoprost may cause BAB disruption in normal dogs while topical dorzolamide/timolol may have no effect on the BAB in normal dogs.     

Effects of travoprost 0.004% compared with latanoprost 0.005% on the intraocular pressure of normal dogs

PURPOSE: To compare the effects of travoprost 0.004% and latanoprost 0.005% on the intraocular pressure (IOP) of normal dogs. METHODS: Twenty mixed breed dogs were randomized to two groups: latanoprost was used in group A and travoprost in group B. The drugs were instilled in the right eye of the dogs, whereas the left eye received placebo. Both drugs were instilled once a day at 8 am during 5 days. IOP measurements were made at 8 am, 10 am, 2 pm and 8 pm during the 5 days of treatment, the 3 days that preceded treatment, and 3 days following treatment. Presence of blepharospasm, miosis, anterior chamber flare, and conjunctival hyperemia were evaluated during the study. RESULTS: Mean IOP was significantly reduced in the eyes treated with both latanoprost and travoprost, when compared with the eyes treated with placebo (P<0.05). There was no statistically significant difference between the mean IOPs of eyes treated with latanoprost and travoprost at all time intervals during baseline, treatment, and recovery (P>0.05). On the fifth day of treatment and on the first day of the recovery period, a severe ocular hypotension was noted with both drugs, resulting in imprecise readings with the tonometer. Miosis and conjunctival hyperemia were observed in the treated eyes of both groups, whereas flare was noticed in one latanoprost-treated eye. CONCLUSION: Travoprost 0.004% significantly reduces the IOP in normal dogs. The hypotensive effect obtained with travoprost 0.004% is comparable to that obtained with latanoprost 0.005%.     

A comparison between the effect of topical tafluprost and latanoprost on intraocular pressure in healthy male guinea pigs

This study was aimed to evaluate the effect of 0.0015% preservative-free tafluprost (Zioptan®) and 0.005% preservative containing latanoprost ophthalmic solutions (Lataprost®) on intraocular pressure (IOP) in healthy male guinea pigs (Cavia porcellus). A total of 16 male guinea pigs were randomly assigned to receive one drop of tafluprost or one drop of latanoprost in the right eye. The contralateral eye served as control. IOP was measured using a rebound tonometer at time 0(baseline), after 30 minutes and every 60 minutes for the next three hours and then every three hours for the next 21 hours. Administration of tafluprost and latanoprost was not associated with changes in IOP in the treated eyes. The maximum IOP-lowering effect of the ophthalmic solutions was observed 30 minutes post-instillation in the treated eyes (-1.25 ± 1.50 mmHg, P-value = 0.194 in group A and -1.50 ± 1.29 mmHg, P-value = 0.103 in group B) and returned to normal after 9 and 12 hours in group A and B, respectively. There was no significant difference between the IOP measurements of the right and left eyes in neither groups during the study (repeated measure test and Generalized Linear Mixed Model). The administration of one drop of tafluprost and latanoprost had no significant effect on the IOP of healthy guinea pigs. Further studies are needed in guinea pigs affected by glaucoma to explore the effectiveness of these drugs.     

Effect of different dose schedules of latanoprost on intraocular pressure and pupil size in the glaucomatous Beagle

Objective To evaluate the changes in intraocular pressure and pupil size in glaucomatous dogs after instillation of 0.005% latanoprost (Xalatan, Pharmacia and Upjohn, Kalamazoo, MI, USA) once in the morning, or once in the evening, or twice daily in five‐day multiple‐dose studies. Animals studied Eight Beagles with the moderate stage of inherited primary open‐angle glaucoma. Procedures Applanation tonometry (IOP) and pupil size (PS) measurements were obtained at 8 am, 10 am, 12 noon, 2 pm, and 4 pm in eight glaucoma dogs. Methylcellulose (0.5% as placebo) was instilled in the control eye, and 0.005% latanoprost was instilled in the opposite drug eye. Control and drug eyes were selected using a random table. For these three studies, 0.5% methylcellulose and 0.005% latanoprost were instilled the second through the fifth days with instillations in the morning (8.30 am), or evening (8 pm), or twice daily (8.30 am and 8 pm). Statistical comparisons between drug groups included control, placebo, and treated (0.005% latanoprost) eyes for three multiple‐dose studies. Results In the 8‐am latanoprost study, the mean ± SEM diurnal declines in IOP for the placebo and drug eyes for the first day were 6.5 ± 3.6 mmHg and 8.4 ± 4.0 mmHg, respectively. The mean ± SEM diurnal changes in IOP after 0.005% latanoprost at 8 am once daily for the next four days were 23.3 ± 5.0 mmHg, 25.4 ± 2.1 mmHg, 25.7 ± 1.7 mmHg, and 26.1 ± 1.7 mmHg, respectively, and were significantly different from the control eye. A significant miosis also occurred starting 2 h postdrug instillation, and the resultant mean ± SD pupil size was 1.0 ± 0.1 mm. In the first day of the second latanoprost study, the mean ± SEM diurnal changes in the placebo and drug eye IOPs were 11.6 ± 3.8 mmHg, and 12.0 ± 4.4 mmHg, respectively. For the following four days with latanoprost instilled at 8 pm, the mean ± SEM diurnal changes in IOP in the drug eyes were 24.9 ± 2.1 mmHg, 22.4 ± 1.8 mmHg, 21.6 ± 1.9 mmHg, and 26.6 ± 2.2 mmHg, respectively. Compared to the fellow placebo eyes, the diurnal changes in IOP were significantly different. Significant changes in pupil size were similar to the IOP changes, with miosis throughout the day and return to baseline pupil size the following morning before drug instillation. In the last study, the mean ± SEM diurnal changes in IOP for the placebo and drug eyes for the first day were 6.6 ± 2.1 mmHg and 9.4 ± 2.8 mmHg, respectively. For the four subsequent days with latanoprost instilled twice daily, the mean ± SEM diurnal IOP changes were 19.6 ± 1.5 mmHg, 19.1 ± 1.4 mmHg, 19.9 ± 1.7 mmHg, and 20.3 ± 0.7 mmHg, respectively, and were significantly different from the placebo eyes. The mean changes in PS were 3.1 ± 0.7 mm. Conclusion 0.005% latanoprost instilled once daily (am or pm) as well as twice daily produces significant decreases in IOP and PS in the glaucomatous Beagle. The evening instillation of 0.005% latanoprost produced less daily fluctuations in IOP than when the drug was instilled in the morning. 0.005% latanoprost instilled twice daily produced the greatest decline in IOP with the least daily fluctuations, but longer duration miosis.     

Effects of 0.005% latanoprost solution on intraocular pressure in healthy dogs and cats

OBJECTIVE: To evaluate effects of daily topical ocular administration of latanoprost solution on intraocular pressure (IOP) in healthy cats and dogs. ANIMALS: 9 domestic shorthair cats and 14 dogs. PROCEDURE: Latanoprost solution (0.005%) was administered topically to 1 eye (treated) and vehicle to the other eye (control) of all animals once daily in the morning for 8 days. Intraocular pressure was measured twice daily for the 5 days preceding treatment, and IOP, pupillary diameter, conjunctival hyperemia, and blepharospasm were measured 0, 1, 6, and 12 hours after the first 4 treatments and 0 and 12 hours after the final 4 treatments. Measurements continued twice a day for 5 days after treatment was discontinued. Aqueous flare was measured once daily during and for 5 days after the treatment period. RESULTS: Intraocular pressure and pupillary diameter were significantly decreased in the treated eye of dogs, compared with the control eye. Mild conjunctival hyperemia was also detected, but severity did not differ significantly between eyes. Blepharospasm and aqueous flare were not detected in either eye. Intraocular pressure in cats was not significantly affected by treatment with latanoprost. However, pupillary diameter was significantly decreased in the treated eye, compared with the control eye. Conjunctival hyperemia, aqueous flare, and blepharospasm were not detected in either eye. CONCLUSIONS AND CLINICAL RELEVANCE: Once-daily topical ocular administration of latanoprost solution (0.005%) reduced IOP in healthy dogs without inducing adverse effects but did not affect IOP in healthy cats. Latanoprost may be useful for treating glaucoma in dogs.     

Effects of unilateral topical administration of 0.5% tropicamide on anterior segment morphology and intraocular pressure in normal cats and cats with primary congenital glaucoma

Objective To determine the effects of topical 0.5% tropicamide on anterior segment morphology (ASM) and intraocular pressure (IOP) in normal and glaucomatous cats. Animals used Normal cats and cats with inherited primary congenital glaucoma (PCG). Procedures Control IOP curves were performed in untreated normal and PCG cats. In the first experiment, tropicamide was applied OD in eight normal and nine PCG cats. IOP and pupillary diameter (PD) were measured at 0, 30, and 60 min, then hourly until 8 h post‐treatment. In a second experiment, six normal and seven PCG cats received tropicamide OD. High‐resolution ultrasound images were obtained at 0, 1, 5, and 10 h post‐treatment to measure ASM changes. IOP and PD were measured OD at 0, 1, 2, 3, 5, 7, and 9 h. Results In untreated normal cats IOP OU decreased throughout the day. In PCG cats IOP OU had wide fluctuations over time. In normal cats IOP response varied in the treated eye but did not change significantly in untreated eyes. IOP significantly increased from baseline in both eyes of all treated PCG cats. Increases in IOP were associated with some ASM changes. Cats with PCG had a significantly smaller angle recess areas, diminished ciliary clefts and decreased iris‐lens contact. ASM changes were not strongly correlated with IOP in all cats. Conclusions The ASM of PCG cats is markedly different from normal cats, and clinically significant increases in IOP OU occur in cats with PCG after tropicamide treatment. The mechanism for this increase remains unclear.     

Intraocular pressure,specular microscopy,and prostaglandin E2 concentration in dogs with mature and hypermature cataract

This study aimed to evaluate and correlate intraocular pressure (IOP), endothelial cell density (CD), and hexagonality (HEX), and the aqueous humor prostaglandin E₂ (PGE₂) concentration in dogs with mature (MG, n = 8) and hypermature (HG, n = 8) cataracts. Eight laboratory beagles with no ocular abnormalities were included as a control group (CG). The IOP was measured using a digital applanation tonometer. Noncontact specular microscopy was used to evaluate CD and HEX. Samples of aqueous humor were used to determine prostaglandin E₂ concentration using enzyme‐linked immunoassay. Data were compared by anova and Bonferroni's multiple comparison test, and possible correlations among the PGE₂ aqueous concentration and corneal endothelium cell parameters were assessed by Person′s test (P < 0.05). Average values of IOP (P = 0.45) and CD (P = 0.39) were not significantly different between MG, HM, and CG. Average values of HEX were lower, and PGE₂ concentration was increased in the MG and HG in comparison with CG (P < 0.05); however, such parameters did not change significantly between MG and HG (P > 0.05). PGE₂ values did not correlate with IOP, CD, and HEX in any group (P > 0.05). Although there were a small number of dogs studied, our results demonstrated that cataract progression from mature to hypermature did not have a significant change in PGE2 aqueous concentration, IOP, corneal endothelial cell count, or morphology. In addition, PGE₂ concentration was not correlated with parameters of the corneal endothelium or IOP in dogs with mature or hypermature cataracts.     

Effect of topical 0.03% flurbiprofen and 0.005% latanoprost, alone and in combination, on normal canine eyes

Objective Evaluate the influence of topically applied flurbiprofen 0.03% and latanoprost 0.005%, alone or in combination, in normal canines. Animals studied 10 Normal Beagles. Procedures Intraocular pressure (IOP), pupil size, aqueous flare, conjunctival hyperemia, and blepharospasm were evaluated bilaterally five times daily (8 am , 11 am , 2 pm , 5 pm, and 8 pm ). The study consisted of a training and acclimation period, followed by 3, 1‐week experiment periods. A 2‐week washout period occurred between each experiment period. During period 1, all dogs received flurbiprofen (three doses 6‐h apart) in the treated eye, whereas in period 2, all dogs received latanoprost (one dose 24‐h apart). During period 3, both latanoprost (one dose 24‐h apart) and flurbiprofen (three doses 6‐h apart) were administered in the treated eye. Results Flurbiprofen resulted in a mean IOP elevation of 1.1 mmHg (8.65%) in the treated eye, as compared with the control eye. No effect on pupil size, conjunctival hyperemia, or aqueous flare was noted. Latanoprost resulted in a mean IOP reduction of 3.4 mmHg (30.19%). Combined latanoprost and flurbiprofen resulted in a mean IOP reduction of 2.7 mmHg (24.56%). Miosis was noted in the treated eyes during both latanoprost periods, with maximal pupil constriction 3‐h post‐dose. This was followed by relative mydriasis 24‐h post‐dose, persisting 48 h after the last dose. The degree of conjunctival hyperemia varied between individuals. Neither blepharospasm nor aqueous flare was noted at any time point. Conclusion Concurrent administration of latanoprost and flurbiprofen resulted in a 20.41% reduction in the ocular hypotensive effect relative to latanoprost therapy alone.     

Effects of topical 0.5% tropicamide on intraocular pressure in normal cats

The objective of the study was to determine the effect of topical 0.5% tropicamide on intraocular pressure (IOP) in normotensive feline eyes. IOP was measured bilaterally in 70 clinically healthy cats and gonioscopy (and goniophotography) was performed. Thereafter, 50 cats were treated unilaterally with one drop of 0.5% tropicamide. The contralateral, left eye served as a control. In the placebo group consisting of 20 cats, one drop of physiologic saline solution was administered to the right eye. In all cats, IOP of both eyes was measured 30, 60 and 90 min after topical administration. After unilateral tropicamide application, IOP increased significantly both in the right and in the left eye. Maximum average IOP increase was observed at the control measurement performed 90 min after treatment, with an elevation of 3.8 +/- 4.2 mmHg in the right eye and 3.5 +/- 3.6 mmHg in the left eye. Maximum IOP increase after treatment was 18.0 mmHg in the treated eye and 17.0 mmHg in the left eye. Measurements made at 60 min after treatment revealed a significantly higher increase in IOP in the right eye as compared to the left eye (P60 < 0.05), whereas the differences between right and left eye in IOP increase were not significant at 30 and 90 min after mydriatic application (P30 = 0.123; P90 = 0.305). Although tropicamide-induced mydriasis was observed in the treated eye, the contralateral eye did not show any changes in pupillary function at any time. With increasing age of the cats, IOP increase was found to be more moderate, whereas the gender of the cats did not have any significant influence on IOP changes. In the 20 cats in the placebo group, no significant changes in IOP were observed. We conclude that topical 0.5% tropicamide causes a significant elevation of IOP in the treated and untreated eye in normal cats.     

Comparison of Force Plate Gait Analysis and Owner Assessment of Pain Using the Canine Brief Pain Inventory in Dogs with Osteoarthritis

Background

Lameness assessment using force plate gait analysis (FPGA) and owner assessment of chronic pain using the Canine Brief Pain Inventory (CBPI) are valid and reliable methods of evaluating canine osteoarthritis. There are no studies comparing these 2 outcome measures.

Objective

Evaluate the relationship between CBPI pain severity (PS) and interference (PI) scores with the vertical forces of FPGA as efficacy measures in canine osteoarthritis.

Animals

Sixty‐eight client‐owned dogs with osteoarthritis (50 hind limb and 18 forelimb).

Methods

Double‐blind, randomized. Owners completed the CBPI, and dogs underwent FPGA on days 0 and 14. Dogs received carprofen or placebo on days 1 through 14. The change in PS and PI scores from day 0 to 14 were compared to the change in peak vertical force (PVF) and vertical impulse (VI).

Results

PS and PI scores significantly decreased in carprofen‐ compared with placebo‐treated dogs (P = .002 and P = .03, respectively). PVF and VI significantly increased in carprofen‐ compared with placebo‐treated dogs (P = .006 and P = .02, respectively). There was no correlation or concordance between the PS or PI score changes and change in PVF or VI.

Conclusions and Clinical Importance

In these dogs with hind limb or forelimb osteoarthritis, owner assessment of chronic pain using the CBPI and assessment of lameness using FPGA detected significant improvement in dogs treated with carprofen. The lack of correlation or concordance between the change in owner scores and vertical forces suggests that owners were focused on behaviors other than lameness when making efficacy evaluations in their dogs.     

Effect of topical 1% tropicamide on Schirmer tear test results in clinically normal horses

Objective  To observe the effect of topical 1% tropicamide on equine tear production as measured by Schirmer I tear test.
Materials and methods  Fourteen adult horses received one drop of 1% tropicamide ophthalmic solution in one eye and the opposite eye served as the control. The tear production in both eyes was tested at 1, 2, 4, 6, and 24 h after 1% tropicamide administration.
Results  Measurements made 1 h after treatment revealed a significant reduction in Schirmer tear test values in tropicamide treated eyes ( P  = 0.002). The observed decrease in tear production was maintained up to 4 h after treatment ( P  = 0.002). Although tropicamide-induced decrease in STT values was observed in the treated eyes, the contralateral eyes did not show significant changes in Schirmer tear test results.
Conclusion  Single dose of topical 1% tropicamide resulted in statistically significant reduction in Schirmer tear test values in clinically normal horses.     

Normal ocular features, conjunctival microflora and intraocular pressure in the Canadian beaver (Castor canadensis)

Objective The aim of the study was to assess the ocular features, normal conjunctival bacterial and fungal flora, and intraocular pressure (IOP) in the Canadian beaver (Castor canadensis). Sample population Sixteen, apparently healthy beavers with no evidence of ocular disease, and live‐trapped in regions throughout Prince Edward Island. Procedures The beavers were sedated with intramuscular ketamine (12–15 mg/kg). Two culture specimens were obtained from the ventral conjunctival sac of both eyes of 10/16 beavers for aerobic and anaerobic bacterial and fungal identifications. The anterior ocular structures of all beavers were evaluated using a transilluminator and slit lamp biomicroscope. Palpebral fissure length (11/16 beavers), and horizontal and vertical corneal diameters (10/16 beavers) were measured. IOPs were measured in both eyes of 11/16 beavers using applanation tonometry. Both eyes of 3/16 beavers and one eye of 1/16 beavers were dilated using topical tropicamide prior to sedation to effect timely maximal dilation. Culture specimens and IOPs were not evaluated in these four animals. Indirect ophthalmoscopy was performed on 7/8 eyes of these four beavers. Results Conjunctival specimens from all eyes cultured positively for one or more isolates of aerobic bacteria. The most common isolate was Micrococcus spp. (five beavers; 9/20 eyes). Other isolates included a Gram‐positive coccobacilli‐like organism (four beavers; 7/20 eyes), Aeromonas hydrophila (three beavers; 4/20 eyes), Staphylococcus spp. (three beavers; 4/20 eyes), Gram positive bacilli (one beaver; 2/20 eyes), Enterobacter spp. (two beavers; 2/20 eyes), Streptococcus spp. (two beavers; 2/20 eyes), aerobic diphtheroids (one beaver; 1/20 eyes), and Pseudomonas spp. (one beaver; 1/20 eyes). Clostridium sordellii (one beaver; 1/20 eyes) and Peptostreptococcus spp. (one beaver; 1/20 eyes) were the sole anaerobic bacteria isolated. All conjunctival specimens were negative for growth of fungi. Ophthalmic examinations revealed the normal beaver eye and ocular adnexa included dorsal and ventral puncta, a vestigial third eyelid, and a circular pupil. Average palpebral fissure length was 9.36 mm (SD = 1.00) for both eyes. Mean horizontal and vertical corneal diameters of both eyes were 9.05 mm (SD = 0.64) and 8.45 mm (SD = 0.69), respectively. Mean IOP for the right and left eyes were 17.11 mmHg (SD = 6.39) and 18.79 mmHg (SD = 5.63), respectively. Indirect ophthalmoscopic examinations revealed normal anangiotic retinas. Conclusions Gram‐positive aerobes were most commonly cultured from the conjunctival sac of normal beavers, with Micrococcus spp. predominating. The overall mean IOP in ketamine‐sedated beavers was 17.95 mmHg. The beaver, an amphibious rodent, has an anangiotic retina.     

Time-specific intraocular pressure curves in Rhesus macaques (Macaca mulatta) with laser-induced ocular hypertension

Objective To detect and categorize time‐specific variations in daytime intraocular pressure (IOP) found in Rhesus monkeys with laser‐induced ocular hypertension. Procedures Ten male monkeys with argon laser‐induced ocular hypertension in one eye were anesthetized with ketamine hydrochloride, and the IOP measured in both eyes at 7 a.m., 7.30 a.m., and then hourly until 1 p.m. with a Tonopen? XL applanation tonometer. Intraocular pressure time profiles for both eyes in each animal were developed. The means ± SD of the IOPs for both eyes were calculated for the whole 6‐h study period, and the values compared statistically. The difference between the lasered eye mean IOP standard deviation and the normal eye mean IOP standard deviation for each animal during the 6‐h follow‐up was also calculated and compared. Results Mean IOP (± SD) in the glaucoma and normal eyes for the 10 animals during the 6‐h study was 32.6 ± 2.5 and 14.9 ± 2.5 mmHg, respectively. The IOP was significantly higher in the experimental eye than in the normal eye (P = 0.0008). The mean IOP in the lasered eye did not significantly change during the study period, whereas a slight but significant increase in IOP of the normal eye over the study period was recorded (P = 0.003). The variance in IOP in the hypertensive eyes was considerably greater than that in the untreated control eyes. From 7 a.m. to 1 p.m. the IOP declined in five eyes and increased in the other five eyes with laser‐induced ocular hypertension. Conclusions The time‐specific IOP variation pattern in the daytime in the laser treated eyes is significantly greater than the variation in the normotensive eyes. This shows that in order to detect statistical differences between IOP variations induced by an IOP‐reducing drug, and the exaggerated spontaneous IOP variations present in the laser‐induced hypertensive eye, sufficient animals should be included in any study. Understanding the time‐specific IOP variation present in a group of monkeys with laser‐induced ocular hypertension is essential prior to using the model for the evaluation of IOP‐reducing drugs.     

Effects of topical administration of 1% brinzolamide on intraocular pressure in clinically normal horses

Reasons for performing study: Only few drugs with limited efficacy are available for topical treatment of equine glaucoma. Objective: To evaluate the effect of topical administration of 1% brinzolamide on intraocular pressure (IOP) in clinically normal horses. Methods: Healthy mature horses (n = 20) with normal ocular findings, were studied. The IOP was measured 5 times daily (07.00, 11.00, 15.00, 19.00 and 23.00 h) over 10 days. On Days 1 and 2, baseline values were established. On Days 3–5 one eye of each horse was treated with one drop of 1% brinzolamide every 24 h immediately following the 07.00 h measurement. On Days 6–8 the same eye was treated with 1% brinzolamide every 12 h (07.00 and 19.00 h). Measurements on Days 9 and 10 documented the return of IOP to baseline values. Statistical analysis of the data was performed. Results: In the treated eye a significant decrease in IOP compared to baseline values was noted during both the 24 and 12 h dosing periods (P<0.001). During the once‐daily treatment protocol an IOP reduction of 3.1 ±1.3 mmHg (14%) from baseline was recorded. During the twice‐daily protocol a total IOP reduction of 5.0 ± 1.5 mmHg (21%) was achieved. Conclusion: Intraocular pressure was significantly decreased by 1% brinzolamide in a once‐daily and a twice‐daily treatment protocol in normotensive eyes. These findings suggest that brinzolamide might also be effective in horses with an elevated IOP. Potential relevance: This drug may be useful for treatment of equine glaucoma.     

Pulmonary vasculature in dogs assessed by three‐dimensional fractal analysis and chemometrics

Fractal analysis of canine pulmonary vessels could allow quantification of their space‐filling properties. Aims of this prospective, analytical, cross‐sectional study were to describe methods for reconstructing three dimensional pulmonary arterial vascular trees from computed tomographic pulmonary angiogram, applying fractal analyses of these vascular trees in dogs with and without diseases that are known to predispose to thromboembolism, and testing the hypothesis that diseased dogs would have a different fractal dimension than healthy dogs. A total of 34 dogs were sampled. Based on computed tomographic pulmonary angiograms findings, dogs were divided in three groups: diseased with pulmonary thromboembolism (n = 7), diseased but without pulmonary thromboembolism (n = 21), and healthy (n = 6). An observer who was aware of group status created three‐dimensional pulmonary artery vascular trees for each dog using a semiautomated segmentation technique. Vascular three‐dimensional reconstructions were then evaluated using fractal analysis. Fractal dimensions were analyzed, by group, using analysis of variance and principal component analysis. Fractal dimensions were significantly different among the three groups taken together (P = 0.001), but not between the diseased dogs alone (P = 0.203). The principal component analysis showed a tendency of separation between healthy control and diseased groups, but not between groups of dogs with and without pulmonary thromboembolism. Findings indicated that computed tomographic pulmonary angiogram images can be used to reconstruct three‐dimensional pulmonary arterial vascular trees in dogs and that fractal analysis of these three‐dimensional vascular trees is a feasible method for quantifying the spatial relationships of pulmonary arteries. These methods could be applied in further research studies on pulmonary and vascular diseases in dogs.     

Effect of topical tropicamide on tear production as measured by Schirmer's tear test in normal dogs and cats

Objective To evaluate the effect of a single dose of topical 1% tropicamide on tear production as measured by the Schirmer tear test (STT) in the normal dog and cat. Material and methods Twenty‐eight dogs and 32 cats received 50 µl : l of 1% tropicamide in one eye and the opposite eye served as the control. STTs were performed immediately before instillation of tropicamide and then at 1, 4, 8 and 24 h post drug instillation. STT results were compared between the control and treated eyes at the different times. Results Aqueous tear production in dogs, measured by STT, was not significantly reduced. The mean ± SEM STTs for the baseline time for control and tropicamide‐treated eyes were 19.9 ± 0.8 and 20.3 ± 0.8 mm wetting/min, respectively. For the control eyes, the subsequent mean ± SEM STT levels were 20.3 ± 0.9 (1 h), 21.1 ± 0.8 (4 h), 20.1 ± 0.9 (8 h), and 18.7 ± 0.7 (24 h). For the tropicamide‐treated eyes, the subsequent mean ± SEM STT levels were 19.4 ± 0.9 (1 h), 19.3 ± 0.9 (4 h), 20.0 ± 0.9 (8 h), and 18.4 ± 0.8 (24 h). Aqueous tear production of both eyes was significantly reduced in cats at 1 h but returned to baseline by 4 h post tropicamide instillation. The mean ± SEM STT levels for the baseline time in cats for control and tropicamide‐treated eyes were 14.9 ± 0.8 and 14.7 ± 0.8 mm wetting/min, respectively. Subsequent mean ± SEM STT levels for the control eyes were 6.4 ± 1.1 (1 h), 11.9 ± 1.0 (4 h), 13.9 ± 0.8 (8 h), and 16.4 ± 1.0 (24 h). For the tropicamide‐treated eyes, the subsequent mean ± SEM STT levels were 5.3 ± 0.8 (1 h), 10.2 ± 0.8 (4 h), 14.7 ± 1.0 (8 h), and 16.6 ± 1.0 (24 h). Conclusion Single dose 1% tropicamide does not significantly lower tear production rates, as measured by the STT, in normal dogs. However, in normal cats single doses of 1% tropicamide in one eye cause significant reductions in tear production of both eyes at 1 h that recovered to baseline levels by 4 h.     

Effect of Coherin™ on intraocular pressure,pupil size and heart rate in the glaucomatous Beagle: a pilot study

Objective To evaluate effects of Coherin? on intraocular pressure (IOP), pupil size (PS), and heart rate (HR) in glaucomatous Beagles in single‐dose studies in a pilot study. Materials and methods Intraocular pressure, PS, and HR were measured in eight glaucomatous Beagles. One randomly chosen eye received single 50 μL doses of differing concentrations of Coherin? (treated eye) or vehicle (placebo‐treated eye), and the fellow eye served as the untreated control. After the first measurements, a single dose of either Coherin? or sterile water vehicle was instilled in the drug and placebo eyes, respectively. Results The mean ± SEM diurnal changes in IOP after 0.005%, 0.01%, 0.2%, 0.284%, 1%, 2%, and 4% topical Coherin? once daily were 7.6 ± 3.2 mmHg, 15.5 ± 5.3 mmHg, 11.2 ± 4.4 mmHg, 11.8 ± 4.4 mmHg, 19.1 ± 3.8 mmHg, 5.0 ± 1.8 mmHg, and 8.8 ± 2.8 mmHg, respectively. The declines in IOP were significantly different (P < 0.05) from the untreated control eyes with the 0.2% and 0.284% Coherin?‐treated eyes and suggestive for 1% Coherin? concentrations. No signs of irritation, significant PS, and HR changes were detected in the Coherin?‐treated eyes. Conclusion Of seven different concentrations, 2% and 0.248% Coherin? produced significant declines in IOP in the glaucomatous beagle in single‐dose studies when compared to both untreated control and placebo‐treated eyes. One percent Coherin? solution produced significant IOP decreases compared with the placebo‐treated eye but not the untreated control eyes. No local ocular irritation, PS and HR changes were observed in Coherin?‐treated eyes. This pilot study suggests that topical Coherin? has potential as an ocular hypotensive agent.     

Changes in intraocular pressure associated with topical dorzolamide and oral methazolamide in glaucomatous dogs

Objective To compare the reduction in intraocular pressure (IOP) by topical 2% dorzolamide to oral methazolamide (5 mg/kg) in dogs, and determine if the combination of both drugs would reduce IOP more than either drug administered alone. Animals studied Thirteen glaucomatous beagles. Procedures Measurements, including applanation tonometry, pupil size and heart rate, were obtained at 8 am, 12 noon, and 5 pm on days 1, 3 and 5. The 5‐day drug studies included placebo (0.5% methylcellulose); 2% dorzolamide administered in one eye twice daily (8 am and 5 pm), and repeated again in one eye three times (8 am, 12 noon and 5 pm) daily; methazolamide (5 mg/kg per os administered at 8 am and 5 pm); 2% dorzolamide instilled twice daily (5 days) combined with oral methazolamide on the last 3 days, and methazolamide (5 days) combined with 2% dorzolamide on the last 3 days and instilled twice daily. Statistical comparisons between drug groups included control (nondrug) eye and treated (placebo/drug) eyes for days 1, day 3 and 5. Results Topical 2% dorzolamide, administered twice and three times daily, significantly decreased IOP (mean ± SEM) in glaucomatous dogs on the first day (twice daily 7.6 ± 2.4 mmHg, and three times daily 16.4 ± 3.6 mmHg) that was even greater by day 5 (twice daily 10.4 ± 2.0 mmHg, and three times daily 13.9 ± 2.7). Oral methazolamide also significantly lowered IOP in both eyes. Oral methazolamide (administered from day 1 through to day 5) combined with 2% topical dorzolamide (instilled in the drug eye for day 3 through to day 5) also significantly lowered IOP of both eyes for all days, and for day 5 the mean ± SEM IOP was decreased by 7.9 ± 1.7 mmHg (methazolamide plus dorzolamide) and 7.5 ± 2.6 mmHg (methazolamide only). Topical dorzolamide (instilled in the drug eye for day 1 through to day 5) combined with oral methazolamide (administered from day 3 through to day 5) significantly lowered IOP in the drug eye on day 1 (5 pm: 9.6 ± 1.9 mmHg), for day 3 (11 am and 5 pm) and for all of day 5 for both eyes (5 pm: control eye 9.5 ± 1.8 mmHg; drug eye 9.2 ± 1.9 mmHg). Topical dorzolamide (2%) instilled three times daily produces similar IOP declines compared to the combination of oral methazolamide and 2% dorzolamide administered twice daily. Conclusions Dorzolamide (2%) instilled twice or three times daily causes significant decreases in IOP in glaucomatous dogs. Twice daily instillations caused progressive declines in IOP from day 1 to day 5. Dorzolamide (2%) combined with oral methazolamide (5 mg/kg per os twice daily) produces similar but not additional declines in IOP.     

Effect of oral administration of carprofen on intraocular pressure in normal dogs

The aim of this study was to determine the effect of oral administration of carprofen on intraocular pressure in normal dogs. Twelve young adult beagle dogs were randomly assigned to treatment (n = 6) or control (n = 6) groups. After an 11‐day acclimation period, the treatment group received approximately 2.2 mg/kg carprofen per os every 12 h for 7 days, and the control group received a placebo gel capsule containing no drug per os every 12 h for 7 days. Intraocular pressure (IOP) was measured by a rebound tonometer at three time points per day (8 am, 2 pm, and 8 pm) during the acclimation (days 1–11) and treatment (days 12–18) phases and for 48 h (days 19–20) after the completion of treatment. There was no statistically significant change in IOP for either eye in the dogs receiving oral carprofen during the treatment phase (days 12–18). After day 4, no significant daily IOP changes were seen in control group dogs. Carprofen administered orally every 12 h for 7 days had no effect on IOP in normal beagle dogs. An acclimation period to frequent IOP measurements of at least 5 days is necessary to establish baseline IOP values and minimize possible anxiety‐related effects on IOP measurements.