Gonioscopic findings in 69 Leonberger dogs in Switzerland from 2019 to 2023

The present study provides an overview of gonioscopic findings in Leonberger dogs in Switzerland and describes glaucoma cases within this sample population. Purebred Leonberger dogs participated in this prospective, multicenter, cross-sectional study. A full hereditary eye disease (HED) examination including gonioscopy was performed in all dogs according to the European College of Veterinary Ophthalmologists (ECVO) HED scheme. The morphology of the pectinate ligament and the width of the iridocorneal angle (ICA-width) were noted and categorized into grades 0-3 and 0-2, respectively. Sixty-nine dogs (137 eyes) with a median age of 2 years and 8 months were included in the study. Pectinate ligament abnormality (PLA) and iridocorneal angle width (ICA-width) were combined to final scores of iridocorneal angle abnormality (ICA-abnormality). Twenty percent (14/69) of all eyes displayed severely affected iridocorneal angles (ICA-abnormality grade 3), 36 % (25/69) moderately affected (ICA-abnormality grade 2) and 31 % (21/69) mildly affected (ICA-abnormality grade 1). Overall, 87 % of the Leonbergers in this study showed some form of iridocorneal angle abnormality. Four percent (6/137) of all eyes, corresponding to 6 % (4/69) of dogs, developed glaucoma between the ages of 5,5-6 years. All of these eyes displayed severely affected ICAs (ICA-abnormality grade 3). A significant number of Leonberger dogs in Switzerland demonstrate iridocorneal angle abnormalities and are at an increased risk for developing primary angle closure glaucoma. Leonberger breeders should be encouraged to have gonioscopy performed on all potential breeding animals, as per the ECVO HED guidelines.