Quantifying refractive error in companion dogs with and without nuclear sclerosis: 229 eyes from 118 dogs.

OBJECTIVE: To evaluate the relationship between nuclear sclerosis (NS) and refractive error in companion dogs. ANIMALS STUDIED: One hundred and eighteen companion dogs. PROCEDURES: Dogs were examined and found to be free of significant ocular abnormalities aside from NS. NS was graded from 0 (absent) to 3 (severe) using a scale developed by the investigators. Manual refraction was performed. The effect of NS grade on refractive error was measured using a linear mixed effects analysis adjusted for age. The proportion of eyes with >1.5 D myopia in each NS grade was evaluated using a chi-square test. Visual impairment score (VIS) was obtained for a subset of dogs and compared against age, refractive error, and NS grade. RESULTS: Age was strongly correlated with NS grade (p < .0001). Age-adjusted analysis of NS grade relative to refraction showed a mild but not statistically significant increase in myopia with increasing NS grade, with eyes with grade 3 NS averaging 0.58-0.88 D greater myopia than eyes without NS. However, the myopia of >1.5 D was documented in 4/58 (6.9%) eyes with grade 0 NS, 12/91 (13.2%) eyes with grade 1 NS, 13/57 (22.8%) eyes with grade 2 NS, and 7/23 (30.4%) eyes with grade 3 NS. Risk of myopia >1.5 D was significantly associated with increasing NS grade (p = .02). VIS was associated weakly with refractive error, moderately with age, and significantly with NS grade. CONCLUSIONS: NS is associated with visual deficits in some dogs but is only weakly associated with myopia. More work is needed to characterize vision in aging dogs.

Duration of Mydriasis Produced by 0.5% and 1% Tropicamide in Sprague-Dawley Rats.

Ophthalmic examination (OE) is a common part of preclinical studies. Pupillary dilation to facilitate OE may affect results of other planned testing. The purpose of this study was to determine the duration of mydriasis produced by commercially available 0.5% and 1% tropicamide in ophthalmologically normal albino rats. Twelve female Sprague-Dawley rats were used. A single drop of 1% tropicamide was applied to one eye of each rat. A single drop of balanced salt solution (BSS) was applied to the contralateral eye. Measurements of pupillary diameter (PD) were obtained using a digital caliper at 0, 20, 40, 60, 120, 180, 240, 300, and 360 min after application. After a 3-wk washout period, the procedure was repeated using 0.5% tropicamide. Pupillary dilation sufficient to allow posterior segment evaluation was achieved with 0.5% and 1% tropicamide. Maximum PD after treatment with 0.5% tropicamide was 4.17 ± 0.22 mm at 40 min; maximum PD after treatment with 1% tropicamide was not significantly different (4.28 mm at both 20 and 40 min (±0.43 mm and 0.23 mm, respectively)). Mean PD remained above 3.5 mm in treated eyes for 60 min. In eyes treated with 0.5% tropicamide, mean PD was significantly different from baseline mean PD for that eye up to 300 min. In eyes treated with 1% tropicamide, mean PD was significantly different than baseline mean PD for that eye at all timepoints. Both concentrations of tropicamide produced a transient mild to moderate mydriasis in the contralateral eye. Duration of action is at least 5 h for 0.5% tropicamide and 6 h for 1% tropicamide. Results of this study support use of 0.5% tropicamide for OE in albino rats, with administration performed no more than 60 min prior to examination.