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Annie Oh, Melanie Louise Foster, Michael G Davidson, Freya M Mowat; Detailed phenotypic characterization of a Beagle dog with the complete form of Schubert Bornschein congenital stationary night blindness.. Invest. Ophthalmol. Vis. Sci. 2017;58(8):286.
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Congenital stationary night blindness (CSNB) is a genetically and clinically heterogeneous retinal disorder resulting in non-progressive impaired night vision. Naturally occurring CSNB affecting inner retinal circuitry (Schubert Bornschein form) was previously described in a closed colony of Japanese Beagle dogs exhibiting a “negative-type” electroretinogram (ERG). We report the detailed phenotype of naturally occurring Schubert Bornschein CSNB in a Beagle dog obtained from a research animal breeding facility in the USA.
A 6-month old, female intact affected Beagle dog and three unrelated age-matched normal control Beagles were studied. Animals underwent ophthalmic examination, streak retinoscopy, and advanced ocular imaging including spectral domain optical coherence tomography (SD-OCT) and autofluorescence imaging. Retinal function assessment included behavioural visual navigation ability, full-field dark- and light-adapted ERG, and evaluation of dark adaptation.
The affected Beagle had a normal fundus appearance, normal retinal layer thickness on SD-OCT, and normal autofluorescence. The affected dog was mildly hyperopic (+1.5D OU) and exhibited vision impairment in mesopic conditions (light intensity 0.02-1 cds/m^2). The affected dog maneuvered more slowly (16.12 +/- SEM 4.46 seconds vs. control 5.37 +/- 1 seconds) and made more incorrect exit tunnel choices (21.43 +/- 9.22 % vs. control 0%) during behavioral visual navigation testing. A reduced b-wave amplitude and a normal a-wave was present on dark-adapted ERG, oscillatory potentials were absent. A normal a-wave with reduced b/a-wave ratio was present on light-adapted flash ERG. The light adapted 33Hz flicker ERG had reduced amplitude and long-flash ERG revealed abnormalities in ON-bipolar cell responses. Maximal dark adaptation was prolonged (>60 minutes).
The main findings of vision impairment in lower light conditions and a “negative-type” ERG in this Beagle are consistent with complete Schubert-Bornschein CSNB.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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