Interexaminer agreement of gonioscopy examinations in dogs using the European College of Veterinary Ophthalmologists Hereditary Eye Diseases grading scheme.

Objective: Prospective observational study with preregistered study protocol to assess interexaminer agreement using the 2022 European College of Veterinary Ophthalmologists Hereditary Eye Disease (ECVO-HED) gonioscopy grading scheme.

Animals studied: Sixty client-owned dogs presented for gonioscopy as part of the required certification process prior to breeding.

Procedure: Two ECVO diplomates with comparable clinical experience performed gonioscopy with a Koeppe gonioscopy lens and slit-lamp biomicroscope at 10x magnification on all eyes in a randomized fashion.

Results: One hundred and eighteen of 120 eyes (60 dogs) were included. In 110/118 eyes (93%), both examiners provided the same breeding recommendation (yes/no). This translated into an agreement on the final breeding recommendation in 58/60 dogs (97%). Examiners disagreed on pectinate ligament abnormality (PLA) grading in 19/118 eyes and iridocorneal angle width (ICAW) grading in 9/118 eyes. PLA grading disagreement was mostly observed between neighboring grades. Disagreement between PLA and ICAW grading sometimes occurred within the same eye accounting for an observed disagreement in iridocorneal angle abnormality (ICAA) grading in 19/118 eyes in total. Cohen's kappa was Κ = 0.62 (95% TI 0.34-0.89), whereas maximum kappa was maxΚ = 0.82 (95% TI 0.59-1). Mixed model analysis suggested no significant examiner influence on breeding recommendations (OR 0.17; 95% CI 0.02-1.12, p = .09).

Conclusions: Although examiners disagreed on ICAA grading in 19/118 eyes, this resulted in a different breeding recommendation (yes/no) in eight eyes and in two dogs only. Therefore, the use of the 2022 ECVO-HED gonioscopy grading scheme seems to result in examiners providing the same breeding recommendations in most cases.