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

Topical Ocular Therapeutics in Small Animals

This article reviews the administration of common topical ophthalmic medications, in relation to factors influencing absorption including composition of topical ophthalmic preparations, and potential systemic effects. Commonly prescribed, commercially available topical ophthalmic medications are discussed with respect to pharmacology, their indications for use, and adverse effects. Knowledge of topical ocular pharmacokinetics is essential for the management of veterinary ophthalmic disease.

Surgical outcome of cats treated for aqueous humor misdirection syndrome: a case series

OBJECTIVE

To evaluate the clinical outcome of cats treated surgically for aqueous humor misdirection syndrome.

METHODS

A retrospective analysis of cats treated surgically between January 1, 2006, and January 1, 2013, for aqueous humor misdirection syndrome was performed. Signalment, medical therapy, eyes affected, intraocular pressures prior to and after surgery, surgical procedures performed, postoperative complications, and visual status were evaluated.

RESULTS

Seven cats (nine eyes) fit the inclusion criteria. Six of seven cats were female, and five of seven cats were diagnosed with bilateral aqueous humor misdirection syndrome. Three surgical approaches were evaluated as follows: (i) phacoemulsification and posterior capsulotomy, (ii) phacoemulsification, posterior capsulotomy and anterior vitrectomy, and (iii) phacoemulsification, posterior capsulotomy, anterior vitrectomy, and endocyclophotocoagulation. The mean age at diagnosis was 12.9 years. Seven of nine eyes had controlled intraocular pressure (≤25 mmHg) during the first 6 months postoperatively. All cats were visual with controlled intraocular inflammation at 1 year postoperatively; however, one eye had an elevated intraocular pressure. All cats were continued on topical antiglaucoma and anti-inflammatory medications following surgery with the mean number of drops per day decreasing from 3.9 drops/day prior to surgery to 2.2 drops/day postoperatively.

CONCLUSIONS

Surgical management for feline aqueous humor misdirection syndrome may be a viable option to maintain a visual and normotensive status in cats that no longer have successful control of intraocular pressure with medical therapy.

Effect of topical latanoprost 0.005% on intraocular pressure and pupil diameter in normal and glaucomatous cats

OBJECTIVE

To determine the effects of latanoprost on intraocular pressure (IOP) and pupil diameter (PD) in cats with inherited primary congenital glaucoma (PCG) and normal cats.

ANIMALS STUDIED AND PROCEDURES

IOP and PD were measured in both eyes (OU) of 12 adult cats (six normal, six PCG), three times per week for 3 weeks prior to, for 3 weeks during, and for 2 weeks following twice-daily treatment with 0.005% latanoprost to the right eye (OD) and vehicle to the left (control) eye (OS). IOP and PD were measured hourly, for 8 h, 1 day prior to, and on the first and last days of treatment. Aqueous humor flow rate (AHF) was determined at baseline and at the end of the treatment phase in six normal cats.

RESULTS

Mean IOP was significantly lower in treated vs. control eyes of PCG cats, for up to 8 h following a single latanoprost treatment, and a maximal IOP reduction of 63% occurred in treated eyes at 3 h. Latanoprost acutely lowered IOP in cats with PCG, but this effect appeared to diminish over 3 weeks of treatment. AHF was modestly increased in the treated eyes of normal cats after 3 weeks of latanoprost treatment, although IOP was not significantly affected. Latanoprost caused miosis, with rebound mydriasis at 24 h posttreatment, in the treated eyes of all cats.

CONCLUSIONS

Further research is needed to determine the suitability and efficacy of latanoprost treatment for long-term IOP-lowering in cats with PCG or other forms of glaucoma.

Effects of ocular administration of ophthalmic 2% dorzolamide hydrochloride solution on aqueous humor flow rate and intraocular pressure in clinically normal cats

OBJECTIVE

To determine the effects of ocular administration of ophthalmic 2% dorzolamide hydrochloride solution on aqueous humor flow rate (AHFR) and intraocular pressure (IOP) in clinically normal cats.

ANIMALS

20 clinically normal domestic shorthair cats.

PROCEDURES

Following an acclimation period, IOP was measured in each eye of all cats 5 times daily for 3 days to determine baseline values. Fifteen cats received 1 drop of 2% dorzolamide solution and 5 cats received 1 drop of control solution in each eye every 8 hours for 5 days (treatment phase). The IOP of each eye was measured 5 times during each day of the treatment phase. Prior to and after the treatment phase, AHFR in both eyes of each cat was measured via fluorophotometry.

RESULTS

Prior to treatment, AHFR or IOP did not differ between the treatment and control groups. In dorzolamide-treated cats, mean AHFR after the treatment phase (3.47 ± 1.5 μL/min) was significantly lower than the value prior to treatment (5.90 ± 2.2 μL/min) and mean IOP during the treatment phase (11.1 ± 1.0 mm Hg) was significantly lower than the baseline mean IOP (14.9 ± 1.0 mm Hg). In the control group, IOP values did not differ before or during the treatment phase and AHFRs did not differ before and after the treatment phase.

CONCLUSIONS AND CLINICAL RELEVANCE

Ocular administration of 2% dorzolamide solution significantly decreased AHFR and IOP in clinically normal cats. Application of 2% dorzolamide solution may be an effective treatment in cats with glaucoma.

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.

Feline glaucoma--a comprehensive review

Cats with glaucoma typically present late in the course of disease. It is likely that glaucoma in cats is under-diagnosed due to its insidious onset and gradual progression, as well as limitations of some commonly used tonometers in this species. Treatment of glaucoma in feline patients presents a clinical challenge, particularly as glaucoma is often secondary to other disease processes in cats. In this review, we consider the clinical features, pathophysiology, and classification of the feline glaucomas and provide current evidence to direct selection of appropriate treatment strategies for feline glaucoma patients.

Effects of topical levobunolol or fixed combination of dorzolamide-timolol or association of dorzolamide-levobunolol on intraocular pressure, pupil size, and heart rate in healthy cats

The effects of topical levobunolol with the fixed combination of 2% dorzolamide-0.5% timolol and the association of 2% dorzolamide with 0.5% levobunolol on intraocular pressure (IOP), pupil size (PS), heart rate (HR), and conjunctival hyperemia in eighteen halthy cats were investigated and compared. IOP, PS, HR, and conjuntival hyperemia were daily recorded at three times (9a.m., 2p.m., and 6p.m.). Three groups were formed (n=6), and one eye of each animal was randomly selected and treated with topical levobunolol (L), or commercial combination of dorzolamide-timolol (DT), or the association of dorzolamide with levobunolol (DL). The first day (0) consisted of recording of baseline values. On the next four consecutive days, drugs were instilled at 8a.m. and 8p.m. and measurements were taken at the same times fore cited. Comparing with the baseline values, all evaluated parameters significantly decreased (P<0.001). Conjuntival hyperemia was not seen. Levobunolol significantly declined IOP, PS, and HR in normal cats, and showed a stronger effect in lowering HR, when compared to dorzolamide-timolol effect. No synergistic effect in IOP declining was noted when levobunolol dorzolamide was added to levobunolol.

Feline primary open angle glaucoma

OBJECTIVES

We have documented the histomorphological features of feline primary open angle glaucoma.

DESIGN

A retrospective morphologic study of eight affected eyes from eight cats, from 1992 to 2006 extracted from a pathology collection, which includes 4000 feline submissions and 1100 cases of feline glaucoma.

PROCEDURE

Sections of affected globes, stained with H&E or with alcian blue were examined with a light microscope. Eyes that did not fulfill the criteria for primary open angle glaucoma were excluded from the study.

RESULTS

The mean age was 9.1 years. Five cats were female and three cats were male. The breeds included five DSH, two Burmese, and one DLH cat. Significant histomorphological findings included an open irido-corneal angle with an open ciliary cleft in all cases, loss of ganglion cells in eight of eight cases, cupping and gliosis of the optic nerve head in four of four cases in which the optic nerve was adequately sampled, and myxomatous changes of the stroma surrounding the vortex veins in seven of eight cases.

CONCLUSIONS

Primary open angle glaucoma in cats is a rare disease that should be taken into consideration when investigating cases of feline glaucoma. The pathogenesis of aqueous outflow obstruction in these cases is not known. This study describes eight additional cases of feline primary open angle glaucoma in cats without an identified cause.

Effects of topical 2% dorzolamide hydrochloride alone and in combination with 0.5% timolol maleate on intraocular pressure in normal feline eyes

OBJECTIVE

To evaluate the effect of topical 2% dorzolamide alone, and in combination with topical 0.5% timolol, on intraocular pressure (IOP) in normal cats.

ANIMALS

Twenty-four healthy Domestic Short-haired cats.

PROCEDURE

Baseline values of IOP were established at 7 am, 10 am, 1 pm, 5 pm and 9 pm during pretreatment phase (days 1-2). During treatment phase (days 3-10) cats received 2% dorzolamide HCl q 12 h in group A (n = 6), q 8 h in group B (n = 6), and combined with 0.5% timolol maleate q 12 h in group C (n = 6). Cats in control group D (n = 6) received artificial tears q 8 h. During treatment phase IOP measurements were continued at the same time-points as in the pretreatment phase.

RESULTS

Mean pretreatment IOP in all cats was 18.46 +/- 2.99 mmHg. Mean IOP decreased significantly (P < 0.0086) in all treatment groups compared to pretreatment values (group A: 16.40 +/- 0.49 mmHg, group B: 16.04 +/- 0.49 mmHg, group C: 17.76 +/- 0.49 mmHg). IOP did not decrease in control group D (18.55 +/- 0.49 mmHg). The difference in IOP between treatment groups (A, B, C) was not statistically significant, but comparison of IOP between each treatment group and the control group was statistically significant (A-D; P = 0.0057; B-D, P = 0.0012; C-D, P = 0.0212).

CONCLUSION

Topical 2% dorzolamide significantly lowers IOP in normal cats but the effect is mild. Concomitant application of 2% dorzolamide and 0.5% timolol does significantly decrease IOP, but the effect is not significantly greater than q 8 h administration of dorzolamide alone.

Goniodysgenesis associated with primary glaucoma in an adult European Short-haired cat

A 9.5-year-old, male castrated European Short-haired (ESH) cat was presented with bilateral glaucoma associated with pectinate ligament dysplasia and an open iridocorneal angle (ICA) upon gonioscopy. The right eye (OD) was avisual and slightly enlarged; the left eye (OS) was still visual. Intraocular pressure (IOP) had been controlled with medical therapy over a 1.5 year-period in both eyes (OU). Eventually IOP could not be adequately controlled medically and the painful and blind right eye was enucleated and transscleral diode laser cyclophotocoagulation was performed twice in the left eye with less than optimal results and progressive loss of vision. Histopathology of the right eye showed goniodysgenesis characterized by failure of differentiation of the pectinate ligament, which existed as a solid sheet of uveal tissue at the entrance of a hypoplastic ciliary cleft, which contained loose mucoid mesenchymal tissue. The trabecular meshwork was hypoplastic and the scleral venous plexus could not be identified. Other findings of chronic glaucoma were inner retinal atrophy, optic nerve atrophy with disc cupping, scleral thinning, peripheral corneal vascularization and pigmentation, and mild focal iridal mononuclear inflammatory cell infiltrate.

Circadian rhythm of intraocular pressure in cats

OBJECTIVE

To evaluate the rhythm of intraocular pressure (IOP) in healthy domestic cats with no evidence of ocular disease and to analyze the influence of photoperiod, age, gender and ocular diseases on diurnal-nocturnal variations of cat IOP.

ANIMALS

All animals were Domestic Short-haired cats; 30 were without systemic or ocular diseases, classified as follows: 12 male intact adult cats, five intact adult female, five adult spayed female, and eight male cats; the latter were less than 1 year of age. In addition, five adult cats with uveitis and three adult cats with secondary glaucoma were included.

PROCEDURE

IOP was assessed with a Tono-Pen XL at 3-h intervals over a 24-h period in 12 healthy adult male cats kept under a photoperiod of 12-h light/12-h darkness for 2 weeks. Eight animals from the same group were then kept under constant darkness for 48 h, and IOP was measured at 3-h intervals for the following 24 h. In addition, IOP was assessed at 3 p.m. and 9 p.m. in five intact females, five spayed females, and in eight young cats, as well as in five adult cats with uveitis and three glaucomatous cats.

RESULTS

Consistent, daily variations in IOP were observed in animals exposed to a light-dark cycle, with maximal values during the night. In cats exposed to constant darkness, maximal values of IOP were observed at subjective night. Differences of IOP values between 3 p.m. and 9 p.m. (diurnal-nocturnal variations) persisted in intact females, spayed females, and young animals, as well as in uveitic and glaucomatous eyes.

CONCLUSIONS

The present results indicate a daily rhythm of cat IOP, which appears to persist in constant darkness, suggesting some level of endogenous circadian control. In addition, daily variations of cat IOP seem to be independent of gender, age, or ocular diseases (particularly uveitis and glaucoma).

Feline glaucomas

Cats are usually presented at a very late stage in the course of glaucoma when the eye is already blind. Secondary glaucoma because of another underlying ocular lesion is the most common form of glaucoma in the cat and is frequently associated with chronic anterior uveitis or intraocular neoplasia. Chronic stages of glaucoma in the cat are characterized by buphthalmus, anterior lens luxation, and exposure keratitis secondary to the enlarged globe. Ophthalmoscopic signs of glaucomatous retinal degeneration are only noticed in very advanced stages. Treatment of glaucoma in cats is usually aimed to keep the eye comfortable and within a normal intraocular pressure range. However, many antiglaucoma medications that are successfully used in humans and dogs are not very well tolerated by cats and, therefore, the selection of recommended drugs is limited in this species.

Ophthalmic emergencies

Ophthalmic emergencies are common presenting complaints in an emergency room. Most ophthalmic emergencies can be treated and stabilized until an ophthalmologist can be consulted. Most ocular emergencies involve loss of vision, compromised globe integrity, or severe ocular pain. Delay in treating true emergencies may result ina blind eye or loss of an eye. This article discusses the clinical signs,diagnosis, and treatment as well as the prognosis of some of the more common ophthalmic emergencies.

Ocular hypotensive drugs

The glaucomas are vision-threatening diseases that commonly result in blindness. In addition to knowledge of the at-risk breeds and predisposing factors for glaucoma as well as the clinical signs of the disease, regular IOP screening with tonometry is required to confirm glaucoma and to monitor the status of the eye. Early intervention with a combination of medications that are capable, in a given species, of reducing aqueous production and increasing aqueous outflow as well as potentially reducing progressive neurosensory degeneration is key to the medical management of this disease.