Evaluation of Refractive Measurements Using a Handheld Autorefractor (Retinomax K+ Screen) Versus Streak Retinoscopy in Dogs

Abstract

Objective: To evaluate the accuracy and clinical applicability of the handheld autorefractor Retinomax K+ Screen in comparison to manual streak retinoscopy in non-cyclopleged dogs. Methods: Thirty-four dogs (68 eyes) of 15 different breeds underwent comprehensive ophthalmic examination and refractive assessment using streak retinoscopy and handheld autorefraction. Statistical analyses included the Wilcoxon signed-rank test, Bland–Altman analysis, and Spearman's rank correlation (α = 0.05). Results: Autorefraction was successfully performed in 57 of 68 eyes; 11 eyes were excluded due to insufficient measurement quality. Retinoscopy yielded a mean spherical equivalent of 0.13 ± 1.04 diopters (D), while autorefraction produced significantly more hyperopic values (mean 0.98 ± 1.66 D; p < 0.001). Bland–Altman analysis demonstrated wide limits of agreement (−2.52 to +4.10 D), indicating substantial variability. A moderate positive correlation was found between methods (ρ = 0.49; p < 0.001). Conclusions: The Retinomax K+ Screen provides rapid, non-invasive refractive measurements but systematically overestimates hyperopia and exhibits considerable variability compared to retinoscopy. Despite fast acquisition, inconsistent results and reduced reliability under suboptimal conditions limit the clinical precision of the autorefractor and its use as a screening tool appears questionable under clinical conditions.