The Shih Tzu eye: Ophthalmic findings of 1000 eyes.

PURPOSE: To evaluate the frequency of ophthalmic disorders in Shih Tzus. ANIMALS: Five hundred client-owned Shih Tzu dogs (1000 eyes). PROCEDURES: Medical records of 500 Shih Tzu dogs were reviewed and ophthalmic examination data were collected and analyzed. RESULTS: In total, out of 1000 eyes, 964 (96.4%; OD: 480 eyes, OS: 484 eyes) had at least one ophthalmic abnormality, and only 36 eyes (3.6%; OD: 20 eyes, OS: 16 eyes) were diagnosed as normal. A total of 1375 individual ophthalmic abnormalities were observed in 964 diseased eyes. Fifty-nine different unique diagnoses were made in the study population, and only three conditions [medial canthal entropion (10.4% of eyes; bilateral in 10.2% of dogs), caruncular trichiasis (21.1% of eyes; bilateral in 20.2% of dogs), and reduced tear film breakup time (17.6% of eyes; bilateral in 17.4% of dogs)] affected 49.1% of the eyes. CONCLUSION AND CLINICAL RELEVANCE: Findings suggested that the most prevalent disorders for the Shih Tzus were hairy caruncle, reduced TBUT, medial canthal entropion, keratoconjunctivitis sicca, pigmentary keratitis, lagophthalmos, and mature cataract.

Tear film breakup time and Schirmer tear test in normal dogs: Effects of age, sex, reproductive status, skull type, and nasolacrimal duct patency.

OBJECTIVE: The present study aimed to determine the effects of age, sex, reproductive status, skull type, and nasolacrimal duct (NLD) patency on tear production and tear film breakup time (TBUT) in normal dogs. ANIMALS STUDIED: The ophthalmic data of 82 healthy adult dogs were evaluated in this study. PROCEDURES: Age, sex, breed, and reproductive status were recorded. Schirmer tear test (STT) and TBUT were assessed in all dogs, and interferometry was available for the selected dogs. The Jones test was used to evaluate NLD patency. The cephalic index (CI) was calculated for each dog (skull width/skull length ×100). RESULTS: Mean (SD) values for the STT results for the right (OD) and left (OS) eyes were 20.6 (2.7) and 20.2 (2.7) mm/min, respectively. Mean (SD) TBUT values for OD and OS were 6.5 (2.5) and 6.1 (2.3) mm/min in all dogs, respectively. Sex and reproductive status had no significant effect on STT and TBUT (P[OU] > 0.05). Skull type significantly affected TBUT in both eyes (P(OD)  = 0.01, P(OS)  = 0.003), but had no effect on STT (P[OU] > 0.3). Age had no correlation with STT and TBUT in either eye (P[OU] > 0.05). STT and TBUT had no correlation in either eye (P[OU] > 0.2). NLD patency had no significant effect on STT or TBUT (P[OU] > 0.1). CONCLUSIONS: The results of this study showed lower TBUT values in brachycephalic breeds than in non-brachycephalic breeds. A compensatory increase in STT values was observed in dogs with low TBUT values.

Effects of 0.0015% preservative-free tafluprost on the equine eye.

OBJECTIVE: The purpose of this study was to determine the effects and potential side effects of topical preservative-free (PF) tafluprost 0.0015% in ophthalmologically normal horses. ANIMALS: Five adult grade horses. PROCEDURES: One of the eyes of each horse was randomly chosen as the "treatment" eye, and consequently, the contralateral eye served as the "control." A single dose of PF tafluprost 0.0015% (0.2 mL) was instilled in the treated eye of each horse. Intraocular pressure (IOP), Schirmer's tear test (STT) levels of each eye, and an ophthalmic examination were performed at T0 (baseline), T30, T120, T24 h, and T48 h. RESULTS: The mean IOP values of the treated eyes at baseline (T0), T30, T120, T24 h, and T48 h were 25.4 ± 4.8 mmHg, 21.2 ± 1.92 mmHg, 15.20 ± 2.48 mmHg, 18.40 ± 1.51 mmHg, and 24.60 ± 1.94 mmHg, respectively. Significant differences were observed between the mean baseline IOP level and the T120 and T24 h time points (p = .001 and p = .009). The mean STT levels at each time point showed insignificant fluctuations during the study (p = .140). Adverse effects such as chemosis and episcleral injection were observed 30 min after the instillation of tafluprost 0.0015% (T30). Blepharospasm and conjunctival hyperemia were observed 120 min (T120) after the administration of the medication. CONCLUSION AND CLINICAL RELEVANCE: Tafluprost 0.0015% showed potential in reducing IOP, but due to its local side effects, it is not a good candidate for management of glaucoma in horses. Tafluprost did not notably affect STT.

Comparison of conjunctival microbiota of clinically normal Persian cats with and without nasolacrimal duct obstruction.

OBJECTIVE: This study was performed to determine the conjunctival microbiota of Persian cats with and without nasolacrimal duct obstruction (NLDO). ANIMALS STUDIED: Twenty-five Persian cats: 15 with bilateral NLDO (Group A) and 10 with no NLDO (Group B). PROCEDURES: All fifty eyes were assessed. Sterile swab applicators were used for the collection of specimens, which were cultured. PCR was performed on conjunctival swab and blood samples for the detection of Mycoplasma spp. and feline herpesvirus 1(FHV-1), respectively. RESULTS: FHV-1 was detected in two cats in Group A. Twelve eyes from Group A and four from Group B were Mycoplasma spp. positive based on the PCR results. Moreover, fungal culture was positive in six eyes from Group A and three eyes from Group B. The dominant fungus isolated was Aspergillus spp. (6 out of 11 fungal isolates). Other isolated fungi were Alternaria spp. and Cladosporidium spp. Twenty-three eyes had positive bacterial culture in Group A, while twelve eyes were positive in Group B. The most commonly isolated bacteria were Staphylococcus epidermidis (15 out of 38 bacterial isolates). ß-hemolytic Streptococcus spp., Corynebacterium spp., and Staphylococcus aureus were isolated in similar proportions in both groups. Escherichia coli was also present in both groups. CONCLUSIONS: Results of this study revealed same isolated fungal and bacterial spp. and in similar proportions in Persian cats with and without NLDO.

Intraocular Pressure Measurements Using Rebound Tonometry in Eight Different Species of Companion Birds.

The purpose of this study was to determine reference interval intraocular pressure (IOP) values in 8 different species of companion birds. One hundred and nineteen companion birds (238 eyes) from a captive colony were examined: 21 pigeons (Columba livia; 18%), 17 African grey parrots (Psittacus erithacus; 14%), 22 common mynahs (Acridotheres tristis; 18%), 24 cockatiels (Nymphicus hollandicus; 20%), 12 zebra finches (Taeniopygia guttata; 10%), 9 budgerigars (Melopsittacus undulatus; 8%), 6 domestic canaries (Serinus canaria domestica; 5%), and 8 ring-necked parakeets (Psittacula krameri; 7%). Intraocular pressure was measured by rebound tonometry (TonoVet) avoiding induced, undesired pressure on the head, neck, or eyes. Mean IOP values varied by species. Mean (± SD) IOP values determined for each species were pigeon (5.42 ± 2.06 mm Hg), African grey parrot (4.93 ± 1.91 mm Hg), common mynah (6.22 ± 2.04 mm Hg), cockatiel (5.08 ± 1.76 mm Hg), zebra finch (5.90 ± 2.11 mm Hg), budgerigar (5.88 ± 2.31mm Hg), canary (5.83 ± 1.60 mm Hg), and ring-necked parakeet (6.25 ± 1.75 mm Hg). No statistically significant differences were found in IOP values between right and left eyes for the species studied (P > .22), with the exception of the ring-necked parakeet (P = .001). The results of this study provide representative IOP values measured using rebound tonometry in 8 different species of companion birds.

Pilot evaluation of the circadian rhythm of tear production in a population of healthy adult cats.

OBJECTIVES: The purpose of this study was to determine if a circadian rhythm exists in Schirmer's tear test (STT-1) values in a group of healthy adult cats. ANIMALS STUDIED: Twenty adult neutered Domestic Short-haired cats (DSH) were used in the study. PROCEDURES: Tear production was measured with the Schirmer tear test (STT-1) at 12 different time points over a 48-hour period. RESULTS: A significant difference (approximately 4.3 mm/min) was noted between STT-1 values measured between 4 pm (lowest) and 12 am (highest) on both day 1 (P = 0.02) and day 2 (P = 0.01), and substantial variation in STT-1 values was observed at different times during the 48-hour period. CONCLUSIONS: Significant variation in mean STT-1 values demonstrates that there is a circadian rhythm in tear production in cats and thus shows the importance of taking the time of day into account when measuring STT-1 in cats.

Effect of body position, eyelid manipulation, and manual jugular compression on intraocular pressure in clinically normal cats.

OBJECTIVE: To determine the effect of body position, eyelid manipulation, and manual jugular compression on intraocular pressure (IOP) in clinically normal cats. ANIMAL STUDIED: TWENTY-ONE ADULT CLIENT-OWNED DOMESTIC SHORTHAIR CATS: PROCEDURES: The IOP was measured by means of rebound tonometer. A baseline IOP was measured in all cats in ventral recumbency with normal head position (horizontal to the ground) with no pressure on the neck or eyelids. To measure the IOP in dorsal recumbency, each cat was held in the dorsal recumbency position for 5 min. Four different manipulations were used, including maximal dorsoventral extension of the eyelids, lateral eyelid extension, manual compression of the ipsilateral jugular vein, and manual compression of both jugular veins. IOP after all the manipulations was measured in ventral recumbency. RESULTS: Overall the mean ± SD IOP values of all eyes in ventral recumbency, dorsal recumbency, maximal dorsoventral extension of the eyelids, lateral eyelid extension, compression of the right jugular vein, compression of the left jugular vein, and compression of the both jugular veins were 16.1 ± 2.9 mmHg, 17.1 ± 5.0 mmHg, 21.7 ± 5.8 mmHg, 22.4 ± 5.6 mmHg, 15.0 ± 3.7 mmHg, 14.9 ± 3.7 mmHg, and 16.1 ± 4.6 mmHg, respectively. IOP was increased significantly in maximal dorsoventral extension of the eyelids (P = 0.001) and lateral eyelid extension (P = 0.001) compared to baseline. CONCLUSIONS: Results of this study may be beneficial for clinicians to be aware of the effects of body position, traction, and compression of the eyelids and neck on IOP during ophthalmic examination in cats.

Strip meniscometry in dogs, cats, and rabbits.

OBJECTIVE: The purpose of this study was to establish the normal values of strip meniscometry (SM) as a lacrimal function test and to compare the results with Schirmer tear test I (STT I) in dogs, cats, and rabbits. ANIMALS STUDIED: Sixty healthy adult dogs from twelve different breeds (120 eyes), twenty adult healthy domestic shorthair cats (40 eyes) and eighteen adult healthy New Zealand white rabbits (36 eyes) were used in this study. PROCEDURES: Lacrimal function was tested by SM tube in all animals. After 24 h at the same time of day, tear production was measured using STT I. RESULTS: Mean SM and STT I values for all of the dogs, cats, and rabbits were 9.66 ± 2.15 mm/5 s and 15.10 ± 3.06 mm/min; 10.50 ± 0.7 mm/5 s and 11.00 ± 1.41 mm/min; 4.72 ± 1.20 mm/5 s and 4.22 ± 2.47 mm/min, respectively. There was a correlation (r = 0.281; P = 0.018) between SM and STT I values in dogs, but no correlation was observed in cats and rabbits (P = 0.61, P = 0.06). No correlation was found between age of animals and obtained SM values in each species (P > 0.29). Sex had no effect on SM values in each species (P > 0.08). CONCLUSIONS: The result of this study provided the normal clinical values of strip meniscometry as lacrimal function test in three species.

EVALUATION OF CONJUNCTIVAL MICROBIOTA IN CLINICALLY NORMAL PERSIAN SQUIRRELS ( SCIURUS ANOMALUS).

This study aimed to evaluate the bacterial flora in the conjunctival fornix of clinically normal Persian squirrels ( Sciurus anomalus). Forty healthy Persian squirrels of equal gender distribution with similar ages (approximately 2 yr) were used for this study. A total of 80 conjunctival swabs were taken from both the right and left eyes of each squirrel for aerobic and anaerobic bacterial identification. A slit-lamp examination was conducted and no external ocular disease was identified. From 80 normal eyes, Staphylococcus spp. comprised the most frequently isolated organism (83%), while Corynebacterium spp. were the second most frequently isolated bacteria (56%), followed by Streptococcus spp. (53%), Chlamydia spp. (33%). Mycoplasma spp. (30%), Pseudomonas spp. (23%), Escherichia coli spp. (12.5%), Enterococcus spp. (7%), and Micrococcus spp. (4%) were also isolated. The most frequently isolated bacteria from the conjunctival fornix of healthy Persian squirrels were Staphylococcus spp. followed by Corynebacterium spp.

Measurement of tear production and intraocular pressure in ducks and geese.

OBJECTIVES: The purpose of this study was to establish a reference value of tear production and intraocular pressure in clinically normal ducks and geese. ANIMAL STUDIED: The study population consisted of forty-eight ducks (24 males and 24 females) and fifty-two geese (26 males and 26 females). PROCEDURES: Birds were gently physically restrained in dorsoventral position without any pressure to the head and neck. Tear secretion and intraocular pressure were measured using 5-mm-wide Schirmer tear test strips and TonoVet® rebound tonometer, respectively. RESULTS: Overall mean ± 2SD STT and IOP values of all eyes were 6.2 ± 2.2 mm/min and 10.2 ± 2.2 mmHg, respectively, for the ducks; 5.5 ± 2.6 mm/min and 9.1 ± 2.0 mmHg, respectively, for the geese. There was no statistically significant difference in IOP between left eye and right eye or between males and females in ducks (P = 0.56, P = 0.63) and geese (P = 0.23, P = 0.22). Analysis of variance revealed that there were no significant differences in the STT and IOP between the breeds in ducks (P = 0.49, P = 0.68) and geese (P = 0.14, P = 0.26). CONCLUSIONS: Results of this study may be beneficial for the diagnosis and therapeutic monitoring of ducks and geese affected with Keratoconjunctivitis sicca, glaucoma, and uveitis.

Effects of oral administration of trimethoprim-sulfamethoxazole on tear production in clinically normal guinea pigs.

OBJECTIVE: To determine the effects of short-term oral administration of trimethoprim-sulfamethoxazole on tear production in clinically normal guinea pigs. ANIMAL STUDIED: Thirty-two healthy adult Abyssinian guinea pigs were used in this study. PROCEDURE: One day before the start of the trial, the pretreatment baseline phenol red thread test (PRTT) values were recorded. Sixteen guinea pigs in the treated group received 25 mg/kg trimethoprim-sulfamethoxazole orally twice a day for 14 days. The other sixteen guinea pigs were used as untreated controls and received a placebo during the study. All the ophthalmic tests were performed without chemical restraint. PRTT values were evaluated in both eyes of all the guinea pigs using a commercial PRTT strip of a single lot number on days 0 (baseline), 15, and 21 after starting the trial. RESULTS: The pretreatment baseline mean ± SD PRTT values for the treatment and control groups were 11.12 ± 3.82 mm/15 s and 11.93 ± 2.73 mm/15 s, respectively. After 14 days of drug administration, the mean ± SD PRTT values for the treatment and control groups were 10.87 ± 3.11 mm/15 s and 13.00 ± 2.47 mm/15 s, respectively. On Day 21, the mean ± SD PRTT values for the treatment and control groups were 12.62 ± 4.05 mm/15 s and 12.87 ± 2.99 mm/15 s, respectively. Significant decreases in the PRTT values, compared with the pretreatment baseline values, were not observed in the treatment group on Day 15 (P = 0.14) and Day 21 (P = 0.31). CONCLUSIONS: Trimethoprim-sulfamethoxazole did not decrease tear production in the guinea pigs in this study.

MEASUREMENT OF INTRAOCULAR PRESSURE IN THE DOMESTIC PIGEON (COLUMBIA LIVIA).

The purpose of this study was to establish intraocular pressure values in clinically normal pigeons. One hundred (52 male and 48 female) healthy pigeons ( Columbia livia ) of six different breeds, ranging in age from 20 to 51 mo were used in the study. Pigeons were gently physically restrained in a dorsoventral position without any pressure or extension to the head and neck. A rebound tonometer with a disposable probe was held horizontally and 4-5 mm from the central corneal surface. Calibration of the device was set to "P." Overall, the mean ± SD intraocular pressure values of all eyes were 6.1 ± 0.9 mmHg (ranging from 3 to 9 mmHg). Mean ± SD values for left and right eyes were 6.1 ± 1.0 and 6.0 ± 1.2 mmHg, respectively. There was no statistically significant difference in IOP between the left eye and right eye or between males and females (P = 0.49; P = 0.74). Analysis of variance revealed that there were no significant differences in the IOP between the breeds (P = 0.22).

Measurement of Tear Production and Intraocular Pressure in Healthy Captive Helmeted Guinea Fowl ( Numida meleagris ).

We establish reference values of tear production by the phenol red thread test (PRTT) and intraocular pressure (IOP) by rebound tonometry in helmeted guinea fowl ( Numida meleagris ). Aqueous tear production and IOP were measured in 44 (22 males, 22 females) clinically normal captive helmeted guinea fowl. Birds were gently physically restrained in the sitting position without any pressure to the head or neck. In each bird, aqueous tear production was measured by placing phenol red threads in the superior conjunctival fornix, and IOP was measured by using a Tonovet rebound tonometer. Overall mean ± standard deviation (SD) values of PRTT and IOP of all eyes were 16.5 ± 1.3 mm/15 s (ranging from 14-18 mm/15 s) and 9.1 ± 0.9 mm Hg (ranging from 7-10 mm Hg), respectively. No significant differences were found in IOP or PRTT between males and females (P = .76; P = .83, respectively) or between the left and right eyes (P = .34 and .66, respectively) in the guinea fowl. Results of this study may be beneficial for the diagnosis and therapy of keratoconjunctivitis sicca, glaucoma, and uveitis in helmeted guinea fowl.

Effects of short-term oral administration of trimethoprim-sulfamethoxazole on tear production in clinically normal Syrian hamsters.

OBJECTIVE: To determine effects of 14 days of oral administration of trimethoprim-sulfamethoxazole on aqueous tear production in clinically normal Syrian hamsters. ANIMAL STUDIED: Fifteen healthy adult Syrian hamsters. PROCEDURE: Baseline phenol red thread test (PRTT) values were recorded 1 day prior to treatment. Eight hamsters in treated group received 15 mg/kg trimethoprim-sulfamethoxazole orally twice a day for 14 days. The remaining seven hamsters were used as untreated controls and received a placebo. All ophthalmic tests were performed without chemical restraint. PRTT values were evaluated in both eyes of all Syrian hamsters using a commercial PRTT strip of a single lot number. RESULTS: The mean ± SD baseline PRTT values for treatment group and control group were 7.25 ± 1.3 mm/15 s and 5.42 ± 1.13 mm/15 s, respectively. After 14 days of drug administration, the mean ± SD PRTT values for treatment group and control group were 5.62 ± 1.5 and 5.64 ± 0.74, respectively. Significant decreases in the PRTT values, compared with baseline values, were observed in the treatment group on day 15 (P = 0.042). CONCLUSIONS: Trimethoprim-sulfamethoxazole decreased tear production in the hamster in this study.

MEASUREMENT OF INTRAOCULAR PRESSURE USING TONOVET® IN EUROPEAN POND TURTLE (EMYS ORBICULARIS).

Twenty-two captive adult European pond turtles (12 males and 10 females) were unrestrained without sedation while intraocular pressure (IOP) was measured by means of a Tonovet®. Mean±SD IOP values between 8 and 10 am for all turtles were 5.42±0.96 mm Hg (range, 3-9 mm Hg). IOP between the right and left eye and between males and females was not significantly different. There was no correlation between IOP and body weight or body length of animals.

Measurement of Tear Production Using the Phenol Red Thread Test in the Common Mynah ( Acridotheres tristis ).

To evaluate tear production in the common mynah ( Acridotheres tristis ) using the phenol red thread test (PRTT) and to make a comparison of measurements with the PRTT placed in the fornices of lower and upper eyelids, tear production of both eyes in 22 healthy adult captive mynah birds was evaluated. After positioning of threads in the fornices of upper and lower eyelids, the PRTT values of the birds were 17.5 ± 3.1 mm/15 s and 19.2 ± 2.5 mm/15 s, respectively. A significant difference was found between PRTT values for upper eyelids and lower eyelids (P = 0.01). This study provides novel data for normal reference ranges of PRTT values in healthy common mynah birds and shows that a difference is found depending on where the PRTT thread is placed.

Measurement of tear production using phenol red thread and standardized endodontic absorbent paper points in European pond turtles (Emys orbicularis).

The objective of this study was to determine the aqueous fraction of the tear film using the phenol red thread test (PRTT) and paper point tear test (PPTT) in healthy adult European pond turtles (Emys orbicularis). Twenty-four healthy adult European pond turtles were studied. Measurement of tear secretion was performed using the PRTT and standardized endodontic absorbent PPTT. Horizontal palpebral fissure length (HPFL) was measured using digital calipers and was correlated with the weight of the animal. The mean ± SD PRTT, PPTT, and HPFL values for the left and right eyes were 5.12 ± 1.54 mm/15 sec and 4.62 ± 1.76 mm/15 sec; 4.50 ± 1.25 mm/1 min and 4.20 ± 1.53 mm/1 min; and 8.4 ± 0.6 mm and 8.3 ± 0.6 mm, respectively. No significant differences were detected between right and left eyes of individual turtles or between males and females in all tests. This study represents reference values of tear production in European pond turtles obtained from PRTT and PPTT methods and forms an important baseline study in defining the healthy chelonian ocular surface.

Results of phenol red thread test in clinically normal Syrian hamsters (Mesocricetus auratus).

OBJECTIVE: To determine the normal reference range for phenol red thread test (PRTT) values in clinically normal Syrian hamsters (Mesocricetus auratus). ANIMALS: Sixteen healthy adult Syrian hamsters (eight males and eight females) were used in this study. PROCEDURE: Ophthalmic examinations were performed without chemical restraint. PRTT values were evaluated in both eyes of all Syrian hamsters using a commercial PRTT strip of a single lot number. RESULTS: No statistically significant differences between right and left eyes were found for any of the results. The mean ± SD PRTT values for the study population were 6.8 ± 2.5 mm/15 s with a range from 3 to 11.5 mm/15 s. Mean PRTTs in male animals were 5.1 ± 1.2 mm/15 s, whereas mean PRTTs in female hamsters were 8.5 ± 2.3 mm/15 s. Comparison between mean PRTT values in males and females showed a significant difference (P = 0.004). Mean weights for males and females were 80.9 ± 4.8 and 90.6 ± 8.5 g, respectively. No linear relationship between mean PRTT and body weight was found in female (P = 0.46) and male (P = 0.92) hamsters. CONCLUSION: This study provides novel data for normal reference ranges of PRTT values in healthy Syrian hamsters. Results of this study may assist veterinarians in the diagnosis of ocular surface disease and syndromes affecting the tear film in these species.

Effect of Topically Applied 0.5% Apraclonidine Versus 0.5% Timolol Maleate on Intraocular Pressure of Healthy Horses.

This study aims to assess the effect of topical 0.5% apraclonidine on Intraocular pressure (IOP) in horses and compare the effects of timolol maleate 0.5% with 0.5% apraclonidine in the equine eye. Twenty healthy female thoroughbred horses were used. Horses were divided into two groups. Ten horses received single dose of 0.2 mL of 0.5% apraclonidine in one randomly selected eye and the contralateral eye received single dose of 0.2 mL of artificial tears. In the second group, 10 horses received single dose of 0.2 mL of 0.5% timolol maleate in one eye and the opposite eye received single dose of placebo (0.2 mL of artificial tears). Intraocular pressure was measured using rebound tonometer at the baseline and 30, 60, 120, 240, 360 minutes, and 24 hours after topical ophthalmic drops instillation. Any ocular side effects were recorded at each time point. Mean (SD) baseline IOPs of the treated and placebo eyes were 26.2(3.1) and 23.5(3.4) in apraclonidine group, and 25.7(2.6) and 23.2(3.3) in timolol group. In the apraclonidine group, significant reduction in the mean IOP started after 60 minutes (P= .005) and was still present after 24 hours (P < .001). In timolol group, IOP was reduced in the treated eyes, but this reduction was only significant in the treated eyes at T24h (P= .03). The highest reduction in IOP in timolol group was observed at T360 (21.0(2.2); 14.7%). Mean IOP was decreased prominently by apraclonidine compared to timolol in treated eyes. In conclusion, single dose of topical 0.5% apraclonidine reduced IOP significantly among normal horses in the present study. Further investigations are necessary for evaluating efficacy and safety of apraclonidine in horses.

Effect of topical 0.5% tetracaine hydrochloride on intraocular pressure in ophthalmologically normal cats.

OBJECTIVES: The aim of this study was to assess the effect of topical tetracaine hydrochloride 0.5% on intraocular pressure (IOP) in ophthalmologically normal cats. METHODS: Twenty domestic shorthair cats (40 eyes) were used in this study. Each cat was randomly allocated to one of two groups (treatment or control). Baseline IOP (T0) was measured in each cat, and then one drop of tetracaine hydrochloride 0.5% or artificial tears was administered into a randomly chosen eye of each cat in the treatment and control groups, respectively. Repeat IOP measurements were performed at 2 mins (T2), 5 mins (T5), 15 mins (T15) and 30 mins (T30) with a rebound tonometer. RESULTS: Mean baseline IOP in all eyes was 20.6 ± 2.5 mmHg. After the unilateral administration of tetracaine, mean IOP decreased significantly in the treated eye at T2 (P = 0.01). Mean IOP returned to baseline values at T15. The mean IOPs in the treated eyes at T0, T2, T5, T15 and T30 were 20.6 ± 3.3 mmHg, 18.2 ± 2.5 mmHg, 18.2 ± 3.4 mmHg, 20.2 ± 3.2 mmHg and 19.8 ± 2.7 mmHg, respectively. A significant difference in IOP was found at all time points between the tetracaine and control groups (P <0.03). CONCLUSIONS AND RELEVANCE: The results of the present study showed a statistically significant reduction in mean IOP 2 mins after the administration of tetracaine hydrochloride 0.5% in the treated eyes of the cats.