Accuracy of hand-held autorefractometer for refractive examination of dog's eye, and influence of accommodative palsy

Abstract

In veterinary ophthalmology, the retinoscope is primarily used for refractive examination, and reports of the examination with an autorefractometer are rare. In this study, we investigated the accuracy of a hand-held autorefractometer and the influence of accommodative palsy for results of refractive examination for dogs' eyes.
Forty six eyes of 23 laboratory Beagles were assessed. Refractive error (sphere error) was examined with a retinoscope and an autorefractometer (Retinomax K-plus; Nikon) before and after instillation of cycloplegic agent. To evaluate the consistency between retinoscopy and autorefractometry, Student's t-test, Pearson product-moment correlation coefficient, and Bland-Altman analysis were carried out. Student's t-test was also used to evaluate the influence of accommodative palsy.
The values with autorefractometry were significant lower and toward myopia than those with retinoscopy in subject's eyes with and without cycloplegia. In regression analysis, a weak correlation was found in non-cycloplegic eyes. Bland-Altman analysis showed that 45.7% of plotted points were within acceptable clinical range (±0.5 D) in non-cycloplegic eyes, versus 52.2% in cycloplegic eyes, and the autorefractometer was evaluated as being insufficient for a clinical alternative. In comparisons of the refractive values between non-cycloplegic and cycloplegic eyes, those values in cycloplegic eyes were significant higher and toward hyperopia than those of non-cycloplegic eyes on both methods.
It is cleared that hand-held autorefractometers like the Retinomax K-plus should be used with great cautions when the refractive error of dog's eyes is evaluated accurately. It is considered that autorefractometry after cycloplegic agent is an ideal way to minimize the changes of refractive value by accommodation.