Survey of the incidence of pectinate ligament dysplasia and glaucoma in the UK Leonberger population

Objective To determine the prevalence of pectinate ligament dysplasia (PLD) in UK Leonbergers and identify cases affected by glaucoma. Also, to define the spectrum of pectinate ligament (PL) appearance in this breed and determine whether gonioscopic monitoring should be recommended. Animals studied Data were compiled from 78 prospective gonioscopy examinations performed by one author (GF) and retrospective analysis of 233 UK eye scheme certificates (2009-2014). Clinical cases of glaucoma in Leonbergers diagnosed by UK veterinary ophthalmologists, where gonioscopy of the fellow eyes or histology of affected eyes had been performed, were also reviewed. Procedure In the prospective study, intraocular pressure was recorded prior to gonioscopy using a rebound tonometer. Gonioscopy was performed using a slit-lamp biomicroscope with a Koeppe goniolens. PLD was categorized according to the percentage of the iridocorneal drainage angle affected (grade 0 = <25% affected; grade 1 = 25-50% affected; grade 2 = 51-75% affected; and grade 3 = >75% affected), and the degree of narrowing of the angle was noted. Results Of 78 dogs examined prospectively, 64/78 (82%) were grade 0, 7/78 (9%) were grade 1, 3/78 (4%) were grade 2, and 4/78 (5%) were grade 3. A large phenotypic variation was observed. Spearman's rank correlation showed a positive correlation between age and severity of PLD (P < 0.0055). 52 (22%) of Leonbergers examined under the UK eye scheme 2009-2014 were affected by PLD. Five clinical cases of glaucoma were reviewed where gonioscopy had been performed and one where histology was performed. All individuals had grade 3 PLD with gonioscopy of the contralateral eye or severe goniodysgenesis with histological sections of the affected eye. Conclusion This survey suggests the prevalence of PLD is sufficient to justify ongoing screening of Leonbergers.