Vitreous degeneration and associated ocular abnormalities in the dog

Ophthalmic Disease and Screening in Breeding Dogs

This article describes the history and infrastructure associated with canine breed-related eye screening and certification by Diplomates of the American College of Veterinary Ophthalmologists. Some of the common or otherwise particularly problematic specific inherited ophthalmic conditions are discussed.

Long-term evaluation of the effects of vitreous degeneration on cataracts and retinal detachment in dogs

OBJECTIVE

We aimed to track and evaluate the association between vitreous degeneration and the development of cataracts or retinal detachments in dogs over a long period.

ANIMAL STUDIED

Data on vitreous degeneration, cataracts, and retinal detachment in 102 eyes were collected from 68 dogs who underwent ocular ultrasonography at least twice between March 2017 and November 2021 at the Veterinary Medical Teaching Hospital, Konkuk University. The mean follow-up time was 515 ± 256 (mean ± standard deviation; range: 81-1196) days.

PROCEDURE

Development of cataracts and retinal detachment, according to the severity of vitreous degeneration grade (VDG), was evaluated during long-term follow-up.

RESULTS

In the cataract study (87 eyes, 61 dogs), the number of cataracts developed according to VDG (grade: 0-3) were as follows: VDG 0: 1 in 10 (10%) eyes, VDG 1: 15 in 35 (43%) eyes, VDG 2: 15 in 30 (50%) eyes, and VDG 3: 10 in 12 (83%) eyes. It was significantly different among grades (p = .026). In the retinal detachment study (95 eyes, 64 dogs), the number of retinal detachments developed according to each VDG were as follows: VDG 0: 0 in 11 (0%) eyes, VDG 1: 1 in 36 (3%) eyes, VDG 2: 5 in 35 (14%) eyes, and VDG 3: 4 in 13 (30%) eyes. It was also significantly different among grades (p = .019).

CONCLUSIONS

During long-term follow-up, dogs with severe vitreous degeneration had an increased risk of cataract and retinal detachment development than those without or with mild vitreous degeneration.

Whole genome sequencing identifies a homozygous nonsense mutation in the JPH2 gene in Shih Tzu dogs with progressive retinal atrophy

Progressive retinal atrophy (PRA), common autosomal recessive disorder affecting several dog breeds including Shih Tzu, is characterized by degeneration of photoreceptors leading to blindness. To identify PRA genetic variants, three affected and 15 unaffected Shih Tzu and 20 non-Shih Tzu were recruited. Dogs underwent ophthalmologic examination and electroretinography, revealing hallmark retina pathological changes and an abnormal electroretinography in all affected dogs but not in unaffected dogs. WGS was performed. Non-synonymous homozygous variants were searched in coding regions of genes involved in retinal diseases/development; the criterion was that variants should only be present in affected dogs and should be absent in both unaffected and 46 genomes of dogs (from an available evolutionary database). Only one out of the 109 identified variants is predicted to harbor a high-impact consequence, a nonsense c.452A>C (p.L151X) in the JPH2 gene. The genotype of JPH2 variant in all 38 dogs was determined with Sanger sequencing. All three affected dogs, but none of the 35 unaffected, were homozygous for the nonsense variant. JPH2 has been previously found to be expressed in several excitable cells/tissues including retina photoreceptors. Hence, JPH2 is a candidate gene for PRA in Shih Tzu.