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Abstract: Objective: Children with Leber congenital amaurosis (LCA) due to CEP290 mutations show characteristic macular preservation. Spectral domain‐optical coherence tomography (SD‐OCT) is a noninvasive technique to investigate retinal structural changes. Loss of integrity of the ellipsoid zone (EZ) on OCT in people with retinal disease has been associated with loss of visual function and is a useful measure of retinal disease progression. We hypothesized that rdAc felines with Cep290 mutation would have a similar pattern of degeneration, with relative central retinal preservation associated with maintenance of the EZ. Procedures: Fundus imaging, confocal scanning laser ophthalmoscopy, and SD‐OCT cross‐sectional imaging was performed on 11 rdAc cats ranging from 6 months to 10 years of age. Images were collected from the area centralis, visual streak, and the mid‐superior and mid‐inferior retina. Receptor plus (REC+, encompassing the entire length of photoreceptors) thicknesses were measured. Regional rates of degeneration were determined by regression analysis and compared using unpaired t‐tests. The EZ was evaluated for the presence, absence, or loss of definition. Results: RdAc cats showed REC+ thinning over time in all regions. The area centralis and visual streak had a slower rate of thinning than the mid‐peripheral retina. There was loss of integrity of the EZ initially in the more peripheral regions, while its integrity was maintained in the area centralis and visual streak at all ages studied. Conclusions: rdAc cats show preservation of the central retina with maintenance of EZ integrity, which recapitulates findings in human patients. [ABSTRACT FROM AUTHOR]

Objective To describe ophthalmic, functional, structural, and genetical characteristics of progressive retinal atrophy (PRA) in the polski owczarek nizinny (PON) breed of dog. Animals studied clinically Client-owned PON dogs ( n = 82) from Sweden. Procedures Routine examination for presumed inherited eye disease was performed in all dogs. Bilateral full-field electroretinography (ERG) was performed in 11 affected and 4 control dogs. Eyes from one affected dog were studied with light microscopy. DNA samples from 34 Swedish and 30 PON dogs collected by Michigan State University (MSU) were tested for the mutations causing the rcd4 and prcd forms of PRA. Results Sixteen of the eighty-two Swedish dogs were diagnosed with PRA. Slight vascular attenuation, first seen at 4.5 years of age, preceded changes in tapetal reflectivity. The initial ERG changes in affected dogs showed markedly diminished rod responses, while cone responses were barely affected. Eventually, cone responses were also reduced. Retinal morphology showed approximately a 50% reduction of photoreceptor nuclei in the outer nuclear layer. Fourteen of fifteen PRA-affected Swedish dogs and eighteen of twenty of the MSU PRA-affected dogs tested genetically were positive for the rcd4 mutation. All tested dogs were negative for the mutation causing prcd-PRA. Conclusions PRA of PON dogs is a late-onset degenerative disease with slow progression. There is early loss of rod function, while the cone system deteriorates later. The rcd4 mutation in the C2ORF71 gene was associated with the majority of the PRA cases tested. The possibility of additional forms of PRA in the breed cannot be excluded. [ABSTRACT FROM AUTHOR]

Objective To characterize hereditary retinal degeneration in the Abyssinian cat ( rdAc) in a recently established closed colony segregating for the rdAc mutation, and evaluate possible differences in the age of onset and progression of disease phenotype since the initial description of rdAc 25 years ago. The sample size of an earlier study was increased in order to determine the allele frequency in Abyssinian and Somali cats on a worldwide basis. Animals studied Twenty rdAc affected cats from the closed animal facility, 87 Abyssinian and Somali cats for study of genotype–phenotype concordance, and DNA from 131 Abyssinian and Somali cats from Scandinavia, the UK and Australia for evaluation of the rdAc allele frequency. Procedures DNA was extracted from blood and buccal swabs using commercially available kits, followed by genotyping. Ophthalmic examinations were performed in the USA and Sweden by two board-certified veterinary ophthalmologists. Results A greater variation in the age of onset and progression of the disease was observed compared to that previously described. An excellent correlation between genotype and phenotype was observed. A population genetic survey revealed that the rdAc allele is in moderate abundance in the Abyssinian breed in Europe and Australia. Surprisingly, homozygosity for the mutant allele was observed in a Siamese cat with ophthalmoscopic findings similar to those originally described for affected rdAc individuals. Conclusions Alertness to the potential of rdAc is needed on the part of the veterinary ophthalmology community, not only in Abyssinian and Somali cats but possibly also in other related cat breeds. [ABSTRACT FROM AUTHOR]

To study retinal function in cats homozygous and heterozygous for a recessively inherited rod-cone degeneration. Dark-adapted electroretinograms (ERGs) were performed on early affected, heterozygous (ophthalmoscopically normal), and clinically normal, nonrelated cats. Responses to blue stimuli over a 3.9-log unit range were recorded. Lower b-wave amplitudes than normal were observed in heterozygotes and early affected cats. The amplitudes of the heterozygotes took an intermediate position between normal and early affected cats. Normalized amplitude/intensity data suggest a normal dynamic range in carriers. B-wave implicit times in carriers were comparable to those of normal cats. These results show that heterozygotes have an altered retinal function, although they are ophthalmoscopically normal. It is difficult to electrophysiologically differentiate heterozygotes from affected cats with the very early stage of retinal degeneration. [ABSTRACT FROM AUTHOR]

Objective: Children with Leber congenital amaurosis (LCA) due to CEP290 mutations show characteristic macular preservation. Spectral domain-optical coherence tomography (SD-OCT) is a noninvasive technique to investigate retinal structural changes. Loss of integrity of the ellipsoid zone (EZ) on OCT in people with retinal disease has been associated with loss of visual function and is a useful measure of retinal disease progression. We hypothesized that rdAc felines with Cep290 mutation would have a similar pattern of degeneration, with relative central retinal preservation associated with maintenance of the EZ., Procedures: Fundus imaging, confocal scanning laser ophthalmoscopy, and SD-OCT cross-sectional imaging was performed on 11 rdAc cats ranging from 6 months to 10 years of age. Images were collected from the area centralis, visual streak, and the mid-superior and mid-inferior retina. Receptor plus (REC+, encompassing the entire length of photoreceptors) thicknesses were measured. Regional rates of degeneration were determined by regression analysis and compared using unpaired t-tests. The EZ was evaluated for the presence, absence, or loss of definition., Results: RdAc cats showed REC+ thinning over time in all regions. The area centralis and visual streak had a slower rate of thinning than the mid-peripheral retina. There was loss of integrity of the EZ initially in the more peripheral regions, while its integrity was maintained in the area centralis and visual streak at all ages studied., Conclusions: rdAc cats show preservation of the central retina with maintenance of EZ integrity, which recapitulates findings in human patients., (© 2017 American College of Veterinary Ophthalmologists.)