Clinical and electroretinographic characteristics of congenital stationary night blindness in the Appaloosa and the association with the leopard complex.
Abstract: To determine the prevalence of congenital stationary night blindness (CSNB) in Appaloosa horses in western Canada, investigate the association with the leopard complex of white spotting patterns, and further characterize the clinical and electroretinographic aspects of CSNB in the Appaloosa. Methods: Three groups of 10 Appaloosas were studied based on coat patterns suggestive of LpLp, Lplp, and lplp genotype. Methods: Neurophthalmic examination, slit-lamp biomicroscopy, indirect ophthalmoscopy, measurement of corneal diameter, streak retinoscopy, scotopic and photopic full-field and flicker ERGs and oscillatory potentials (OPs) were completed bilaterally. Results: All horses in the LpLp group were affected by CSNB, while none in the Lplp or lplp groups was affected. The LpLp and Lplp groups had significantly smaller vertical and horizontal corneal diameters than the lplp group had. Median refractive error was zero for all groups. Scotopic ERGs in the LpLp (CSNB-affected) group were consistent with previous descriptions. The CSNB-affected horses had significantly longer photopic a-wave implicit times, greater a-wave amplitudes, and lower b-wave amplitudes than the Lplp and lplp (normal) groups did. No differences were present in photopic flicker amplitude or implicit times. Scotopic flickers in the CSNB-affected horses were markedly reduced in amplitude and abnormal in appearance. No differences were noted in OP implicit times; however, amplitudes of some OPs were reduced in CSNB-affected horses. There were no differences in scotopic and photopic or flicker ERGs or OPs between the normal groups. Conclusions: CSNB was present in one-third of horses studied and there was a significant association between CSNB and the inheritance of two Lp alleles. ERG abnormalities support the hypothesis that CSNB is caused by a defect in neural transmission through the rod pathway involving the inner nuclear layer.
Publication Date: 2007-11-01 PubMed ID: 17970998DOI: 10.1111/j.1463-5224.2007.00572.xGoogle Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This research investigates the prevalence of congenital stationary night blindness (CSNB) in Appaloosa horses in Western Canada, its association with the leopard complex (Lp), a set of white spotting patterns, and the electroretinographic characteristics of the condition. The study found CSNB in one-third of the horses studied, significantly linked to horses carrying two Lp alleles.
Research Methodology
- The study involved 30 Appaloosa horses grouped into three based on coat patterns indicative of their genotype (LpLp, Lplp, and lplp).
- A neurophthalmic examination, slit-lamp biomicroscopy, indirect ophthalmoscopy, measurement of corneal diameter, and streak retinoscopy was performed on each horse.
- Light and dark full-field and flicker Electroretinograms (ERGs) and oscillatory potentials (OPs), used to measure the function of cells in the retina, were recorded for each horse.
Research Findings
- All horses in the LpLp group were affected by CSNB, implying a significant link between CSNB and the leopard complex.
- The LpLp and Lplp groups had significantly smaller corneal diameters than the lplp group.
- In terms of refractive error, all groups had a median of zero.
- Scotopic, or low light, ERGs in the LpLp group matched previous descriptions of this in CSNB-affected horses. These horses also displayed longer light sensitive (photopic) a-wave implicit times, greater a-wave amplitudes, and lower b-wave amplitudes than the normal groups.
- There were no differences in photopic flicker amplitude or implicit times, but scotopic flickers in the CSNB-affected horses were notably reduced in amplitude and had a strange appearance.
- No differences were noted in OP implicit times, however, the amplitudes of some OPs were reduced in CSNB-affected horses.
- No differences were found in low-light and light sensitive or flicker ERGs or OPs between the unaffected groups.
Conclusions
- The research discovered CSNB in approximately one-third of the horses studied, and found a significant connection between the condition and the inheritance of two Lp alleles.
- The abnormal ERG results support the hypothesis that CSNB is caused by a defect in neural transmission through the photoreceptive rod pathway in the inner nuclear layer of the retina.
Cite This Article
APA
Sandmeyer LS, Breaux CB, Archer S, Grahn BH.
(2007).
Clinical and electroretinographic characteristics of congenital stationary night blindness in the Appaloosa and the association with the leopard complex.
Vet Ophthalmol, 10(6), 368-375.
https://doi.org/10.1111/j.1463-5224.2007.00572.x Publication
Researcher Affiliations
- Department of Small Animal Clinical Sciences, Western College of Veterinary Medicine University of Saskatchewan, 52 Campus Drive, Saskatoon, Saskatchewan, Canada S7N 584. lynne.sandmeyer@usask.ca
MeSH Terms
- Animals
- Breeding
- Canada / epidemiology
- Diagnostic Techniques, Ophthalmological / veterinary
- Electroretinography / veterinary
- Female
- Genetic Diseases, Inborn / epidemiology
- Genetic Diseases, Inborn / genetics
- Genetic Diseases, Inborn / veterinary
- Hair Color / genetics
- Horse Diseases / congenital
- Horse Diseases / epidemiology
- Horse Diseases / genetics
- Horses
- Male
- Night Blindness / congenital
- Night Blindness / epidemiology
- Night Blindness / genetics
- Night Blindness / veterinary
- Prevalence
Citations
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