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Connie Y. Yeh, Jessica S. Rowlan, Amanda T. Parton-Corr, Shelby L. Reinstein, Andras M. Komaromy; Evaluation of Chromatic Pupillary Light Reflexes and Melanopsin Expression in Inherited Canine Retinal Diseases. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5399.
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To evaluate chromatic pupillary light reflexes (cPLRs) and to determine melanopsin (Opn4) mRNA expression levels in canine models of inherited retinal diseases.
cPLRs were evaluated in adult dogs with rod-cone dysplasia 1 (rcd1), Leber congenital amaurosis (RPE65-LCA), and CNGB3-achromatopsia by use of the Melan-100 system (Biomed Vision Technologies). This device uses bright (200 kcd/m2) red (630 nm) and blue (480 nm) light for the stimulation of canine long- and medium-wavelength-absorbing (L/M) cones and melanopsin-containing intrinsically photosensitive retinal ganglion cells (ipRGCs), respectively. Canine melanopsin cDNA was amplified and sequenced from total retinal RNA using RACE-PCR. Retinal melanopsin gene expression levels were determined by quantitative real-time PCR (qRT-PCR) in dogs affected by rcd1, X-linked progressive retinal atrophy 2 (XLPRA2), and CNGB3-achromatopsia.
While cPLRs to bright red light was diminished or absent in all disease models evaluated, the responses to bright blue light were normal even in animals with advanced rcd1 where rods and cones could no longer be detected histologically. Furthermore, strong dazzle reflexes were elicited with the blue but not the red light in all affected animals. There was no difference in melanopsin gene expression levels between any of the retinal disease models and normal controls.
Diminished/absent pupillary responses to red light combined with normal responses to blue light are good indicators of advanced stages of canine outer retinal disease with primary or secondary involvement of L/M-cones. The maintained responses to blue light were consistent with unchanged melanopsin gene expression levels. This suggests that ipRGCs are preserved in outer retinal disease.
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