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Autosomal recessive retinal degenerative diseases cause visual impairment and blindness in both humans and dogs. Currently, no standard treatment is available, but pioneering gene therapy-based canine models have been instrumental for clinical trials in humans. To study a novel form of retinal degeneration in Labrador retriever dogs with clinical signs indicating cone and rod degeneration, we used whole-genome sequencing of an affected sib-pair and their unaffected parents. A frameshift insertion in the ATP binding cassette subfamily A member 4 (ABCA4) gene (c.4176insC), leading to a premature stop codon in exon 28 (p.F1393Lfs*1395), was identified. In contrast to unaffected dogs, no full-length ABCA4 protein was detected in the retina of an affected dog. The ABCA4 gene encodes a membrane transporter protein localized in the outer segments of rod and cone photoreceptors. In humans, the ABCA4 gene is associated with Stargardt disease (STGD), an autosomal recessive retinal degeneration leading to central visual impairment. A hallmark of STGD is the accumulation of lipofuscin deposits in the retinal pigment epithelium (RPE). The discovery of a canine homozygous ABCA4 loss-of-function mutation may advance the development of dog as a large animal model for human STGD., Competing Interests: I have read the journal's policy and the authors of this manuscript have the following competing interests: A patent application (US No. 62/662,362) has been filed by the following authors and inventors, TB, GA, BE and SM. CM and SR are affiliated with a diagnostic lab marketing genetic tests for dogs. TB, GA and SM are affiliated with a university department that provides genetic testing for animals.

Objective: To describe a slowly progressive retinopathy (SPR) in Shetland Sheepdogs. Animals  Forty adult Shetlands Sheepdogs with ophthalmoscopic signs of SPR and six normal Shetland Sheepdogs were included in the study., Procedure: Ophthalmic examination including slit-lamp biomicroscopy and ophthalmoscopy was performed in all dogs. Electroretinograms and obstacle course-test were performed in 13 affected and 6 normal dogs. The SPR dogs were subdivided into two groups according to their dark-adapted b-wave amplitudes. SPR1-dogs had ophthalmoscopic signs of SPR, but normal dark-adapted b-wave amplitudes. Dogs with both ophthalmoscopic signs and subnormal, dark-adapted b-wave amplitudes were assigned to group SPR2. Eyes from two SPR2 dogs were obtained for microscopic examination., Results: The ophthalmoscopic changes included bilateral, symmetrical, greyish discoloration in the peripheral tapetal fundus with normal or marginally attenuated vessels. Repeated examination showed that the ophthalmoscopic changes slowly spread across the central parts of the tapetal fundus, but did not progress to obvious neuroretinal thinning presenting as tapetal hyper-reflectivity. The dogs did not appear seriously visually impaired. SPR2 showed significantly reduced b-wave amplitudes throughout dark-adaptation. Microscopy showed thinning of the outer nuclear layer and abnormal appearance of rod and cone outer segments. Testing for the progressive rod-cone degeneration ( prcd )-mutation in three dogs with SPR was negative., Conclusion: Slowly progressive retinopathy is a generalized rod-cone degeneration that on ophthalmoscopy looks similar to early stages of progressive retinal atrophy. The ophthalmoscopic findings are slowly progressive without tapetal hyper-reflectivity. Visual impairment is not obvious and the electroretinogram is more subtly altered than in progressive retinal atrophy. The etiology remains unclear. SPR is not caused by the prcd-mutation., (© 2011 American College of Veterinary Ophthalmologists.)

The Jämthund is the fourth most common breed in Sweden with approximately 1600 pups registered each year. Although it has been known that some adult dogs go blind, so they cannot hunt, the Jämthund dog has historically not been screened for hereditary eye diseases. This report describes nine Swedish Jämthund dogs with retinal degeneration. These dogs represent all Jämthund dogs diagnosed with progressive retinal atrophy (PRA) by the Swedish Eye Panel and registered with the Swedish Kennel Club from January 1998 to September 2008. The dogs were examined with indirect opthalmoscopy and slitlamp biomicroscopy. Additionally, electroretinograms (ERGs) following ECVO guidelines were performed in two dogs (one affected and one normal) and the eyes from three affected dogs were examined by light-microscopy postmortem. Typical findings were bilateral symmetric generalized retinal degeneration with tapetal hyper-reflectivity, attenuation of blood vessels and pigment clumping in the nontapetal fundus. These retinal findings progressed with time in two dogs after re-examination. Visual impairment, especially under dim light conditions, was observed in the affected dogs. ERG from one affected dog showed profoundly reduced rod responses, whereas cone responses were better preserved. Microscopic changes in the eyes from three dogs were characterized by a severe diffuse predominantly outer retinal degeneration and atrophy. Re-sequencing of the prcd-gene for eight of the nine investigated dogs revealed that none of the individuals carried disease allele that has been associated with prcd-PRA in other breeds. In conclusion, ophthalmoscopic, electroretinographic, and light-microscopic alterations observed in nine Jämthund dogs were compatible with PRA. The prcd mutation was excluded as a cause of this retinopathy.

Objective: The aim of the study was to evaluate if tonometry and gonioscopy could serve as predictors of later glaucoma development in the English Springer Spaniel, a breed prone to developing primary glaucoma., Animals Studied: Gonioscopy was performed on 279 English Springer Spaniel dogs, 119 males and 160 females, with clinically normal eyes. In addition, 14 dogs, five males and nine females were examined for glaucoma., Results: A positive relation between pectinate ligament dysplasia (PLD) and narrowing of the relative width of the ciliary cleft (RWOCC) and also between PLD, RWOCC and age was demonstrated. The prevalence of PLD was 25.5%, which is higher than in other breeds reported. A positive association was demonstrated between PLD and glaucoma, as well as between narrowing of the RWOCC and glaucoma. Glaucoma was not observed in dogs with normal appearance of the iridocorneal angle. English Springer Spaniels related to dogs with glaucoma show more narrowing of the RWOCC and more PLD than unrelated dogs., Conclusion: This study demonstrates the positive association between PLD and glaucoma, between narrowing of the iridocorneal angle and glaucoma and the effect of age on the iridocorneal angle. Mating of dogs with normal iridocorneal angles appears to reduce the presence and degree of abnormal appearance of the iridocorneal angle in the offspring. However, breeding only dogs with normal iridocorneal angles without consideration of their relationship to dogs with glaucoma is not a guarantee for preventing glaucoma in the offspring.