Intraocular Pressure In Dogs Research Articles

The effect of intravenous hydromorphone alone or in combination with midazolam or dexmedetomidine on intraocular pressure in dogs

ObjectiveTo evaluate the effect of intravenous (IV) hydromorphone alone or in combination with midazolam or dexmedetomidine on intraocular pressure (IOP) in dogs. Study designProspective, randomized, blinded, crossover study. AnimalsA group of seven healthy, ophthalmologically normal, adult Beagle dogs. MethodsA total of four IV drug combinations were evaluated: hydromorphone 0.1 mg kg–1 (H); hydromorphone 0.1 mg kg–1 and dexmedetomidine 0.001 mg kg–1 (HD); hydromorphone 0.1 mg kg–1 and midazolam 0.2 mg kg–1 (HM2); and hydromorphone 0.1 mg kg–1 and midazolam 0.4 mg kg–1 (HM4). Treatment order was randomized, with a 2 week washout period between treatments. IOP and sedation scores were obtained before (T0) and 3, 30, 60, 240 and 480 minutes after drug injection. To account for repeated measurements for each dog across treatments and time points, mixed models were used to compare IOP at T0 by eye and to describe changes from T0 in IOP (averaged across eyes) and sedation scores. ResultsIn treatment H, IOP increased significantly from baseline levels [predicted mean increase of 5.5 mmHg [95% confidence interval (CI): 3.7–7.3] at T3 (p < 0.001) and 2.7 mmHg (95% CI: 0.9–4.5) at T30 (p = 0.005)]. In treatment HD, mean IOP increased from baseline by 2.3 mmHg (95% CI: 0.5–4.1) at T30 (p = 0.014). In treatment HM2, mean IOP increased by 2.5 mmHg (95% CI: 0.2–4.9) at T30 (p = 0.035). In treatment HM4, IOP did not change significantly from baseline at any time point. Sedation scores over time did not differ significantly between treatments. Conclusions and clinical relevanceInjection of IV hydromorphone alone (0.1 mg kg–1) caused a transient increase in IOP and might not be appropriate if an acute increase in IOP is undesirable. Addition of dexmedetomidine or midazolam to hydromorphone, at the doses studied, appears to attenuate this increase in IOP.

Effects of intracameral tissue plasminogen activator injection on posterior capsular opacification, fibrin formation, and intraocular pressure in dogs after phacoemulsification.

To evaluate whether intracameral tissue plasminogen activator (tPA) injection is effective in regulating posterior capsular opacification (PCO), fibrin formation and intraocular pressure (IOP) after cataract surgery. Prospective study involving 30 eyes of 21 dogs that underwent phacoemulsification. Thirty eyes were randomly divided into two groups of 15 eyes (control and tPA groups). Intracameral tPA (25 μg/0.1 mL) was injected into tPA group eyes before corneal incision closure but not into the eyes of the control group. The grades of anterior fibrin formation and PCO were compared based on slit lamp biomicroscope examination at 1 and 2 weeks, 1 month, and 2-3 months postoperatively. IOP was measured using applanation tonometry every 30 min for 4 h immediately after operation and on the following morning. The IOP of the two groups at each time was compared. The grade of anterior fibrin formation and that of PCO were not significantly different between the two groups at any time point (p > .05). However, the IOP of the tPA group was significantly lower than that of the control group at each point on the day of surgery (p < .05). No complications were observed with tPA injection, except for temporary hyphema (for 3 days) in one eye. Although the intracameral tPA injection did not affect anterior fibrin formation and PCO, it effectively maintained normal IOP immediately after phacoemulsification. Thus, our findings provide valuable insights into the potential benefits of intracameral tPA injection in achieving immediate IOP control after phacoemulsification.

Evaluation of lidocaine for auriculopalpebral nerve block in dogs: Onset, duration, and effects on intraocular pressure and eye examination.

Accurate intraocular pressure (IOP) measurement is essential for managing glaucoma, requiring tonometry. Local anesthesia is typically used, but nerve blocks may be needed for blepharospasm. This study investigated the efficacy of auriculopalpebral nerve block with lidocaine in achieving eyelid akinesia and its influence on IOP in dogs. In a randomized, blinded trial, 12 healthy adult mixed-breed dogs (24 eyes) received either auriculopalpebral nerve block with 2% lidocaine (n = 12 eyes) or no block (n = 12 eyes). Tetracaine drops were used for topical anesthesia in half of blocked/non-blocked eyes, and the rest of the eyes got artificial tears as control. The impact of nerve block was evaluated through assessments of menace response, palpebral reflex, and IOP before the block, after drop instillation, and at 15-min intervals until block dissipation. Auriculopalpebral nerve block provided effective eyelid akinesia in 58.5% (7/12 eyes) at 15 min, reaching 91.7% (11/12 eyes) at 30 min, indicating peak efficacy. Subsequently, the block gradually diminished, with 66.7% (8/12 eyes) and 33.3% (4/12 eyes) maintaining akinesia at 45 and 60 min, respectively. Importantly, neither auriculopalpebral nerve block nor tetracaine administration significantly affected IOP measurements (p > .05). Auriculopalpebral nerve block using lidocaine demonstrated efficient eyelid akinesia, peaking at 30 min postinjection. This technique proved to be safe with no notable alterations in IOP, suggesting its potential utility in canine ophthalmology for procedures requiring eyelid akinesia, particularly in the management of glaucoma where maintaining accurate IOP measurements is crucial for diagnosis, treatment, and monitoring the disease.

The effect of intravitreal cidofovir injection on end-stage glaucoma in dogs: a retrospective study of 153 eyes.

To evaluate the long-term efficacy, prognostic factors, and complications of intravitreal cidofovir injection in dogs with end-stage glaucoma. 130 client-owned dogs. Medical records of dogs that underwent intravitreal cidofovir injections were reviewed. A minimum follow-up period of 6 months was required as the inclusion criterion. Signalment, type of glaucoma, preinjection intraocular pressure (IOP), types of applied glaucoma eye drop, coexisting ocular diseases, outcomes, and complications were recorded. Success was defined as IOP of ≤ 25 mm Hg at the 2-week recheck that remained to the 6-month recheck. The overall success rate of intravitreal cidofovir injection was 91.5% (140/153). The success rate of a single injection was 69.3% (106/153), of a second injection was 59.5% (25/42), of a third injection was 42.9% (6/14), of a fourth injection was 33.3% (2/6), and of a fifth injection was 50.0% (1/2). Intraocular pressures at 6 months after injection were relatively higher when the injection was repeated, fewer types of glaucoma eye drop were applied prior to the injection, and cataract stages were advanced at the time of injection (P < .05). The most common complications were phthisis bulbi (42.5%), cataract progression (30.1%), and intraocular hemorrhage (16.3%). Six eyes were enucleated, and 3 were enucleated due to corneal perforation. Intravitreal cidofovir injection had a high long-term success rate in lowering IOP in dogs with end-stage glaucoma.

Comparison of Tonovet® and Tonovet plus® tonometers for measuring intraocular pressure in dogs, cats, horses, cattle, and sheep.

Reference ranges for intraocular pressure (IOP) in healthy animals are device-specific; therefore, it is strongly recommended to use appropriate reference values according to the device. Therefore, our aim was to compare IOP readings made by TonoVet® and TonoVet Plus® in healthy dogs, cats, sheep, cattle, and horses. We compared IOP values measured by TonoVet® and TonoVet Plus® tonometers in clinically normal eyes of dogs, cats, horses, cattle, and sheep. Five groups comprising 20 animals each of dogs (various breeds, 9 months-10 years old, 14 females, 6 males), cats (various breeds, 6 months-12 years old, 8 females, 12 males), horses (various breeds, 5-12 years old, 12 females, 8 males), cattle (Holstein, 1-7 lactation, female), and sheep (Latvian Darkhead ewes, 1-8 years old) were included in the study. Both eyes of all animals were subjected to ophthalmic examination, including evaluation of IOP by rebound tonometry using TonoVet® and TonoVet Plus® devices. Normality was determined using the Shapiro-Wilk test. The independent t-test was used to determine differences between IOP values in the right and left eyes and between both tonometers. This study was approved by the Ethical Commission of the Latvia University of Life Sciences and Technologies (Nr. LLU_Dzaep_2022-2-4). No differences in IOP between the right and left eyes were found in all cases (p > 0.05). The mean IOP ± standard deviation values in both eyes for TonoVet® and TonoVet Plus® tonometers were as follows: for dogs, 15.25 ± 2.73 mmHg and 19.65 ± 3.46 mmHg; and in cats, 18.88 ± 3.98 mmHg and 18.78 ± 4.26 mmHg, respectively. In horses, mean IOP was 22.15 ± 3.74 mmHg and 24.28 ± 3.00 mmHg; in cattle, 24.73 ± 2.89 mmHg and 23.28 ± 2.97 mmHg; and in sheep, 18.05 ± 3.54 mmHg and 22.49 ± 4.66 mmHg, respectively. Significant differences in IOP values were observed between the tonometers in sheep, dog, and horse groups (mean difference -4.40, -4.48, and 2.13, respectively). This study showed significantly higher IOP values measured by the TonoVet Plus® tonometer in dogs and sheep.

Effects of tiletamine-zolazepam vs. propofol on peri-induction intraocular pressure in dogs: A randomized, masked crossover study.

Anesthesia induction agents have the potential to cause severe ocular side effects, resulting in lasting damage to the eye. The purpose of this study is to determine the effects of tiletamine-zolazepam on IOP compared to propofol when they are used as an induction agent in normal healthy dogs. Twenty healthy adult client owned dogs weighing 22.2 ± 7.6 kg were selected for the study. In a randomized order, all dogs received tiletamine-zolazepam 5 mg/kg IV or propofol 8 mg/kg IV titrated to effect without premedication. Washout between each treatment was at least seven days. IOP measurements were obtained at four time points: baseline, post-induction, post-intubation, and after recovery using applanation tonometry. No additional procedures were performed. After normality of the data was determined, a linear mixed model was built with time, eye, treatment and all interactions of those variables as fixed effects and subject as a random effect. There was no significant difference for age, body weight, drug dose, baseline IOP, and recovery IOP between treatments. Average IOP measurements remained within the normal range of 15-25 mmHg at these time points. However, IOP was significantly less elevated by the tiletamine-zolazepam treatment vs. propofol at the post-induction (mean difference: -4.7 ± 4.6 [95%CI -6.8 to -2.5]) and the post-intubation (mean difference: -4.4 ± 4.6 [95%CI -6.5 to -2.2]) time points. Dogs receiving tiletamine-zolazepam for anesthetic induction had a significantly less elevated IOP at induction and intubation compared to dogs receiving propofol.

Management of canine glaucoma using a combination of dorzolamide and timolol

A study was conducted in twelve glaucomatous dogs to assess the efficacy of the combination of dorzolamide and timolol in the treatment of glaucoma in dogs. The study included twelve dogs with glaucoma of any age, breed, or gender. On the day of presentation, the 14th, 28th and 42nd days, the intraocular pressure (IOP) was monitored with an applanation tonometer. For 42 days, all dogs received topical instillation of a combination of dorzolamide (2%) and timolol (0.5%) eye drops, one drop twice daily. In all the dogs, there was a shift in IOP towards the established normal level within two weeks of therapy. The study revealed that topical use of a combination of dorzolamide and timolol eye drops twice daily was successful in lowering IOP in dogs with glaucoma.

Comparison among TonoVet, TonoVet Plus, Tono-Pen Avia Vet, and Kowa HA-2 portable tonometers for measuring intraocular pressure in dogs.

Background and Aim:Tonometers are an important instrument for measuring intraocular pressure (IOP) in the diagnosis of glaucoma or uveitis. This study aimed to compare the accuracy of the main types of tonometers with different IOP measurement methodologies in dogs: TonoVet and TonoVet Plus (rebound), Tono-Pen Avia Vet (applanation), and Kowa HA-2 (Goldmann applanation).Materials and Methods:IOP was measured in 152 eyes of 76 dogs. A postmortem study was performed by comparing manometry and tonometry values and calculating the correlation coefficient (r2), in vivo real IOP (manometry) among the tonometers was compared, and an outpatient study was conducted with healthy eyes and eyes with signs of glaucoma and uveitis.Results:In the postmortem study, the values of r2 in descending order were Kowa (0.989), TonoVet Plus (0.984), TonoVet (0.981), and Tono-Pen Avia Vet (0.847). The IOP values in mmHg in the in vivo study were as follows: Aneroid manometer (16.8±2.5.7), TonoVet (18.1±2.9), TonoVet Plus (20.6±2.3), Tono-Pen Avia Vet (17.1±2.5), and Kowa (16.1±1.7); in outpatient clinics: TonoVet (16.8±3.8), TonoVet Plus (19.2±2.9), Tono-Pen Avia Vet (16.2±2.4), and Kowa (15.0±1.3); glaucoma: TonoVet (30.2±3.5), TonoVet Plus (35.0±6.1), Tono-Pen Avia Vet (29.5±4.2), and Kowa (23.9±5.0); and uveitis: TonoVet (14.2±1.4), TonoVet Plus (17.6±1.9), Tono-Pen Avia Vet (13.7±2.1), and Kowa (12.6±1.7).Conclusion:There was a strong correlation between IOP values and manometry in all the tonometers. The highest values were obtained with TonoVet Plus and the lowest with Kowa HA-2. All tonometers accurately measured IOP in dogs, including the latest TonoVet Plus, which showed an excellent correlation coefficient.

Evaluation of the applanation tonometer Tono-Pen Avia® Vet™ for the measurement of the canine and feline intraocular pressure

Using tonometers, intraocular pressure (IOP) is merely measured indirectly leading to measurement inaccuracies. All available technical devices are designed for humans, hence a calibration via comparison to manometric measurements is necessary for their use in veterinary medicine. In this study, the applanation tonometer Tono-Pen Avia® Vet™ (TPA) was to be calibrated for use in dogs and cats resulting in the calculation of a correction factor. Additional objectives were the determination of reference values for TPA-derived IOP and the evaluation of possible influence of patient characteristics on measurements results. For the manometric study, 10 enucleated eyes from cats and dogs were subject to IOP measurement with a manometer and the TPA covering the range of 5-60 mmHg. The mean percentage of difference between manometer and TPA was used to calculate correction factors. Subsequently, the TPA was employed to measure the IOP in healthy animals without signs of ocular disease for the determination of reference values. The effect of the patient characteristics age, body weight, and gender on the IOP measurement results was examined using statistical mixed models. With rising intraocular pressure, the TPA underestimated IOP to an increasing degree. Multiplication of the TPA-derived IOP with the factor of 1.5 for dogs and cats resulted in values well in accordance with the manometrically-derived, actual IOP. In the second part of the study, a total of 94 dogs (188 eyes) and 64 cats (128 eyes) were examined. Reference values for the IOP measured with the TPA are 9-18 mmHg for dogs and 9-20 mmHg for cats. For both species, age exhibited a significant influence (dog, p = 0.001 and cat, p = 0.008) on the IOP measurement results in that the IOP-values displayed a decrease with increasing age. The TPA underestimated the actual IOP with increasing intraocular pressure. The calculated correction factor of 1.5 is suitable for the conversion of tonometric IOP results into actual pressure values. The TPA is suitable for the measurement of the IOP in dogs and cats.

Effect of intra-abdominal hypertension on the intraocular pressure of the conscious dogs.

This study was performed to evaluate the effect of intra‐abdominal pressure (IAP) on intraocular pressure (IOP) in conscious dog models using a balloon technique to generate intra‐abdominal hypertension. Six healthy dogs without ocular abnormalities were evaluated in this study. A balloon device was placed in the intra‐abdominal cavity. The abdomen was insufflated to IAP levels of 15 and 25 mmHg using the balloon device. Intraocular pressure was measured at baseline, at IAP levels of 15 and 25 mmHg, and after decompression. In comparison with the mean baseline IOP (15.1 ± 2.0 mmHg), there was a significant increase in IOP at IAP levels of 15 mmHg (20.0 ± 2.1 mmHg) and 25 mmHg (19.9 ± 2.2 mmHg), corresponding to a 32.4% and 31.7% increase from baseline IOP, respectively. The mean IOP after decompression (14.8 ± 1.7 mmHg) was significantly lower compared to those at IAP levels of 15 and 25 mmHg. The present findings demonstrate that increased IAP has a clinically significant effect on IOP in dogs under conscious conditions. Although more research is needed to determine of increased IAP on IOP, these findings suggest that increased IAP leads to mild and reversible increase in IOP.

Effects of orally administered gabapentin, tramadol, and meloxicam on ocular variables in healthy dogs.

To determine the effects of gabapentin, tramadol, and meloxicam on tear production, intraocular pressure (IOP), pupillary diameter, tear break-up time, and corneal touch threshold in healthy dogs when given orally for 3 days. 9 healthy research Beagles. A randomized, blinded, case-crossover study with a 6-sequence, 3-treatment, and 3-period design was performed. A 7-day acclimation period was followed by 3 treatment phases, each with a 3-day treatment period followed by a 7-day washout period for 3 different drugs. Block randomization was used to group dogs for treatments with drug A (gabapentin), B (tramadol), or C (meloxicam). Measurements of tear production, IOP, pupillary diameter, tear break-up time, and corneal touch threshold were performed on a schedule. A generalized mixed-effects linear regression model was created for each ocular variable, accounting for repeated measures within individuals. Intraocular pressure was the only variable to have differed substantially between the first 5 and last 2 days of the acclimation period. When treatment phase, day, time of day, dog identification, baseline value, and eye were accounted for, the mean IOP was lower for dogs during treatment phases with gabapentin or tramadol, compared with meloxicam, but this difference was not considered clinically meaningful. Results indicated that a minimum 5-day acclimation period is necessary for IOP measurements to return to baseline in dogs. The statistically identified effect of gabapentin and tramadol on IOP in dogs of the present study warrants further investigation. It is possible that at higher dosages, or in dogs with glaucoma, this effect may become clinically significant.

Effect of topical administration of 0.1% diclofenac sodium ophthalmic solution at four frequencies on intraocular pressure in healthy Beagles.

To evaluate effects of topical ophthalmic administration of diclofenac on intraocular pressure (IOP) when applied at 4 frequencies to eyes of Beagles. 8 ophthalmologically normal Beagles. The study involved four 5-day experimental periods each separated by a 16-day washout period. During each period, 1 drop of 0.1% diclofenac sodium ophthalmic solution was administered to the right eye at 4 treatment frequencies (1, 2, 3, or 4 times/d); 1 drop of eyewash was administered to the left eye as a control treatment. A complete ophthalmic examination was performed on days 0 (day before first treatment) and 5 of each experimental period. Gonioscopy was performed on day 0 of the first period. The IOPs were measured at 7 am and 7 pm on days 1 through 5. No abnormalities were detected during neuro-ophthalmic and ophthalmic examinations on day 0 of each experimental period. No adverse reactions to administration of diclofenac or eyewash were observed at any time point. No abnormalities were detected during ophthalmic examinations performed on day 5, and IOPs remained < 25 mm Hg in all 4 periods. No significant differences were identified between the treated and control eyes or among the 4 treatment frequencies. Topical ophthalmic administration of diclofenac up to 4 times/d in dogs with no ophthalmic abnormalities did not significantly increase the IOP. Additional research is needed to evaluate the effect of topical ophthalmic administration of diclofenac on IOP in dogs with anterior uveitis.

Comparison of Intraocular Pressure Measurement with Schiotz Tonometer and Tono-Pen Vet Tonometer in Healthy Dogs.

IntroductionMeasurement of intraocular pressure (IOP) in dogs has high diagnostic value because of the possibility of detecting ocular and systemic diseases. Various types of tonometers are available for this measurement in small animal practice. The aim of the study was to compare the IOP values measured with Schiotz and Tono-Pen Vet tonometers in healthy dogs. Clinical diagnostic usefulness of both models was also evaluated.Material and MethodsThe examination was performed in 62 eyes in 31 clinically healthy dogs of different races, gender, and ages.ResultsThe values for intraocular pressure obtained with Schiotz tonometer were in the range of 12 to 24 mmHg, with the mean of 16.3 ± 2.1 mmHg. The intraocular pressure measured with Tono-Pen Vet tonometer was in the range of 11–25 mmHg, with a mean of 18.1 ± 3.8 mmHg. The mean results of measurements taken using the two tonometers differed statistically significantly, the difference being 1.79 mmHg and the higher values being read from the Tono-Pen Vet tonometer.ConclusionCorrelation coefficients calculated for the results obtained in the right and left eyes using two tonometers indicated highly correlative relationships between the results. The study shows that both tonometers can be advantageously used in clinical practice to measure intraocular pressure in dogs.

A review of the pharmacology of osmotic agents for the treatment of glaucoma in dogs

At present, the only proven way to treat glaucoma is to lower intraocular pressure (IOP). Osmotic agents constitute an important class of ocular hypotensive agents. These medications are used for the rapid reduction of IOP, typically in emergency situations, in which IOP is severely elevated and there is a high risk of permanent and irreversible damage of the optic nerve. This paper summarizes the current state of knowledge on the mechanism of action of osmotic agents and their effect on IOP in dogs. Moreover, it discusses the possible undesirable side effects of these medications and presents the current ideas about their role and status in the medical management of canine glaucoma.

Ex vivo and in vivo study of Kowa HA-2 applanation tonometer in the measurement of intraocular pressure in dogs

The objective of this study was to evaluate the use of the Kowa HA-2 applanation tonometer in measuring intraocular pressure (IOP) in dogs. Twenty eyes were used in an ex vivo study in which the calibration curve for manometry vs. tonometry was determined by artificially raising the IOP in 5 mmHg increments up to 60 mmHg (10-60 mmHg). Both eyes of 10 anesthetized dogs were studied in vivo to compare manometry vs. tonometry. In the ambulatory study, 168 healthy eyes, 74 eyes with glaucoma and 60 eyes with uveitis were evaluated by tonometry, which was performed with topical anesthesia and 1% fluorescein eye drops for the formation of fluorescein semicircles. The ex vivo study showed an excellent correlation coefficient (r2= 0.993) between the aneroid manometer and the Kowa HA-2 tonometer. In the in vivo study, there was no significant difference (P&gt;0.05) between the IOP values by manometry and tonometry, showing the excellent accuracy of the Kowa HA-2 tonometer. In the ambulatory study using the Kowa HA-2 tonometer, the IOP values (mean±SD, in mmHg) were 15.1±1.8 (12.0 – 20.0) for the healthy eyes, 25.2±4.0 (20.0 – 38.0) for glaucomatous eyes and 10.1±2.3 (5.0 – 13.7) for eyes with uveitis. There was a strong correlation between the IOP values obtained by direct ocular manometry and those from the Kowa HA-2 tonometer. In the ambulatory study, the IOP values measured by the tonometer were compatible for healthy eyes and for eyes with glaucoma or uveitis. We conclude that Kowa HA-2 applanation tonometer is accurate and practical for IOP measurement in dogs.

A review of the pharmacology of carbonic anhydrase inhibitors for the treatment of glaucoma in dogs and cats

Glaucoma is a heterogeneous group of disorders usually associated with elevated intraocular pressure (IOP), leading to optic nerve damage, retinal ganglion cell death and irreversible vision loss. Therefore, medications that lower IOP are the mainstay of glaucoma therapy. Carbonic anhydrase inhibitors (CAIs) are some of the principal drugs used in the management of canine and feline glaucoma. This paper summarises current knowledge of the mechanism of action of these agents and their effect on IOP in dogs and cats. It also discusses potential harmful side effects of CAIs and presents current opinions about their role and place in the medical management of glaucoma in small animals.

Intraocular pressure, specular microscopy, and prostaglandinE2concentration 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 application of tetracaine on intraocular pressure in dogs: Preliminary results

To evaluate the effect of topical application of tetracaine on intraocular pressure (IOP) measurement by Tonopen in dogs. Six healthy male Epagneul Bretons (group 1) and six healthy male black Labrador Retrievers (group 2) were examined. IOP was measured in the right eye (OD) prior to (IOP1) and 1 minute following instillation of one drop of topical tetracaine (IOP 2), and the left eye (OS) (control) prior to (IOP 3) and 1 minute following instillation of one drop of isotonic saline solution (IOP 4). Measurements were performed on two occasions: at 8:00 AM and 3:00 PM. For both groups, IOP measurements were higher in the morning than in the afternoon. For group 1, IOP1 mean (SD), IOP2 mean (SD), IOP3 mean (SD) and IOP4 mean (SD) were 14.6 (2.2) mmHg, 11.3 (3.2) mmHg, 14.4 (2.2) mmHg and 13.5 (3.9) mmHg respectively, while in group 2, IOP1 mean (SD), IOP2 mean (SD), IOP3 mean (SD) and IOP4 mean (SD) were 14.2 (3.8) mmHg, 9.5 (3.7) mmHg, 13.5 (2.8) mmHg and 13.0 (3.8) mmHg respectively. For both groups at each time point, IOP 2 values were significantly lower (P<0.007) than IOP 1 values, whereas IOP 3 and 4 values were not significantly different (P>0.27). This study demonstrates that topical application of tetracaine significantly lowers IOP measured by Tonopen due to a possible interaction with melanin. The potential effect of topical anesthetics should be taken in consideration when performing applanation tonometry for clinical, pharmacological and toxicological studies.

Effects of oral propranolol or atenolol administration on intraocular pressure in clinically normal dogs

The objective of this study was to determine the effects of oral propranolol or atenolol on intraocular pressure (IOP) in clinically normal dogs. Ten clinically normal dogs with no evidence of ocular disease were randomly allocated into two equal groups. Pretreatment IOPs (T0) were obtained 1 day prior to starting oral propranolol or atenolol in both groups, respectively. Five dogs received oral propranolol (1 mg/kg, q12h) for 2 weeks, while dogs in the other group received oral atenolol (1 mg/kg, q12h) in the same treatment period. Once-a-day measurements of IOP (10:00 AM) were recorded on days 1 (T1), 3 (T3), 5 (T5), 7 (T7), and 14 (T14) in both treatment groups. IOP in dogs, measured by applanation tonometry, was not significantly different between treatment groups throughout the study. In conclusions, orally administered β-adrenergic blocking agents such as propranolol or atenolol have no significant effect on IOP values in clinically normal dogs over a 2-week duration.

Effects of an unfixed combination of latanoprost and pilocarpine on the intraocular pressure and pupil size of normal dogs

To assess changes in intraocular pressure (IOP) and pupil diameter (PD) induced by daily application of an unfixed combination of latanoprost and pilocarpine in normal dogs. Fifteen mixed breed clinically normal dogs of both sexes. Three groups of five dogs each were administered in the right eye, one drop of 0.005% latanoprost (group L), 2% pilocarpine (group P), and 0.005% latanoprost with 2% pilocarpine (group LP), respectively. The left eyes received placebo. Drugs were administered once a day at 8 a.m. over a period of 5 days. IOP and PD measurements were conducted daily at 8 a.m., 10 a.m., 12 noon, 2 p.m., and 4 p.m. from 1 day preceding treatment to 7 days following treatment, and the presence of blepharospasm and/or conjunctival hyperemia was noted. Compared to baseline values, mean diurnal IOPs significantly decreased during the treatment period, by 4.4 (24.4%), 5.8 (31.4%), and 6.1 mmHg (35%) in the L, P, and LP groups, respectively. Compared to placebo-treated eyes, reductions of 2.1(14.1%), 3.2 (20.1%), and 4.1 mmHg (26.6%) were observed for the L, P, and LP groups, respectively. Although mean IOPs in the LP group decreased slightly more than the other two groups, these differences were not statistically significant. Miosis and conjunctival hyperemia were observed in the treated eyes of all three groups of animals during the treatment period. Although both 0.005% latanoprost and 2% pilocarpine individually produced significant decrease in IOP, the topical administration of a combination of latanoprost (0.005%) and pilocarpine (2%) was not associated with a statistically significant synergistic reduction in IOP in dogs; and miosis was the most frequent side effect observed during treatment.