Changes in intraocular pressure and horizontal pupil diameter during use of topical mydriatics in the canine eye

Abstract

The objective of this study was to determine the effects of topical 0.5% tropicamide, 1% atropine sulphate and 10% phenylephrine hydrochloride ophthalmic solutions on intraocular pressure (IOP) and horizontal pupil diameter (HPD) in the dog during the first hour after treatment. Forty clinically and ophthalmologically normal canine patients (between the ages of 2 and 6 years) of varying breed and sex were used in this study. Animals were randomly divided into four groups of ten and given one drop of tropicamide, atropine, phenylephrine or saline into one eye. IOP and HPD were measured in both eyes every 5 minutes for 60 minutes. Tropicamide increased IOP by 8.8±4.0 mmHg 35 minutes post-treatment compared to pre-treatment (P<0.01) only in treated eye. IOP in the contralateral eye did not increase. With atropine the maximum increase in IOP was 2.6±2.8 mmHg at 20 minutes post treatment in the treated eye (P<0.01). IOP in the contralateral eye did not increase. Phenylephrine increased IOP by 2.3±2.1 mmHg (P<0.05) 10 minutes after treatment. Also in the untreated eye IOP increased by 2.3±2.1 mmHg, 20 minutes post-treatment. Maximum HPD in eyes treated with tropicamide occurred at 55 minutes and with atropine at 60 minutes. There were no HPD changes in the contralateral, untreated eye. Topical 10% phenylephrine showed maximal pupil dilation 60 minutes after treatment, but the HPD of the -untreated eye slightly decreased at 15 minutes, but this change only reached statistical significance at 40 min post-treatment (P<0.05). Normal saline showed no influence on IOP or HPD. The drugs investigated here show a significant increase in IOP after mydriatics.

Normal reference ranges of ocular physiology and sonographic biometry of Latvian Hunting dogs

“…In Latvian Hunting dogs, we calculated the normal range of IOP as 11.3-24.1 mmHg (mean±SD of 17.7±3.2 mmHg in both eyes). These values are slightly higher than in a previous study of mixed dog breeds, where IOP ranged from 12.8±1.8 mmHg to 17.7±3.1 mmHg [30] and similar to other author reported values -from 16.7±4.0 mmHg to 18.7±5.5 mmHg [7,31].…”

The effect of central corneal thickness on intraocular pressure values using various tonometers in the dog

“…In addition to sample size, another potential limitation of the study is the use of tropicamide and proparacaine prior to the measurement of IOP, which may have influenced the IOP readings 1 . One recent study showed that tropicamide increased IOP in dogs by 8.8 ± 4.0 mmHg by 35 minutes post‐treatment compared to pre‐treatment, 31 while another study showed that the majority (60%) of dogs displayed 5 mmHg or less in IOP change post‐mydriasis 32 . Topical anesthetics, on the other hand, tend to reduce IOP readings 27,33,34 .…”

Clinical ophthalmological diagnostic description of 10 healthy sugar gliders (Petaurus breviceps) and prevalence of ocular‐related presentations in a larger hospital population

“…Structures posterior to the iris were successfully evaluated with the use of tropicamide 1% eye drops once the pupil was 50%‐60% dilated. Tropicamide‐induced mydriatic induction occurred faster in sugar gliders (7.2 ± 2.7 minutes with a range of 5 to 14 minutes) than in dogs (20 minutes), 12 or another marsupial, the red kangaroo (mean of 16.7 ± 3.34 minutes) 13 . The rapidity of dilation in sugar gliders is convenient for minimizing anesthetic time associated with ophthalmic examination.…”