Achromatopsia in three sibling Labrador Retrievers in the UK

Abstract

Achromatopsia was identified in three Labrador Retriever littermates. The dogs demonstrated day blindness, negotiating obstacles under low-light conditions, but apparently blind when outdoors. One of the dogs presented with immature bilateral diffuse posterior cortical cataracts and clinical signs of day blindness became apparent following cataract extraction surgery. Electroretinography demonstrated an absence of a cone photoreceptor response to a bright stimulus and a flicker response of 30 Hz in all three dogs. No fundic lesions have been apparent ophthalmoscopically in any of the dogs as the initial presentation of each case. No abnormalities were detected with DNA screening for known mutations of the CNGB3 gene in any of the dogs.

Electroretinographic findings in day-blind dogs

“…Rod-driven responses during dark adaptation at 0,4,8,12,16 and 20 min, respectively -single flash of light for each measurement, stimulus intensity 0.01 cd s m -2 ; dark adapted, mixed rod-cone response -two stimuli were averaged with a 15-second interval, stimulus intensity 3 cd s m -2 ; light adaptation time -10 min with white background light of 30 cd m -2 , stimulus intensity 3 cd s m -2three responses were averaged; cone flicker 31 Hz, the same light conditions The 12 dogs included in this study had similar vision testing results to cdaffected dogs (Aguirre and Rubin, 1974;Hurn et al, 2003;Narfström and Petersen-Jones, 2013;Dixon, 2016). As in other reports, among these dogs there were Labrador Retriever (Dixon, 2016) and Alaskan Malamute (Koch and Rubin, 1971;Rubin, 1971a,b) as well as German Shepherd, Dachshund, Yorkshire Terrier, Shih Tzu, Siberian Husky and crossbreed dogs. Under daylight conditions, 9 dogs moved cautiously and collided with obstacles, whereas in dim light they were more active and avoided barriers.…”

“…The disease can be diagnosed from 7-12 weeks of age (Rubin, 1971a,b;Aguirre and Rubin, 1974;Narfström and Petersen-Jones, 2013). Day blindness is a typical sign (Rubin, 1971a,b;Aguirre and Rubin, 1974;Hurn et al, 2003;Narfström and Petersen-Jones, 2013;Dixon, 2016). Under photopic conditions, the dog becomes insecure, moves more carefully and appears to be blind (Rubin, 1971a,b;Hurn et al, 2003;Narfström and Petersen-Jones, 2013;Dixon, 2016).…”

“…Day blindness is a typical sign (Rubin, 1971a,b;Aguirre and Rubin, 1974;Hurn et al, 2003;Narfström and Petersen-Jones, 2013;Dixon, 2016). Under photopic conditions, the dog becomes insecure, moves more carefully and appears to be blind (Rubin, 1971a,b;Hurn et al, 2003;Narfström and Petersen-Jones, 2013;Dixon, 2016). Additionally, under light conditions, dogs with cd can be photophobic, and some of them can show miosis (Rubin, 1971a,b;Hurn et al, 2003, Dixon, 2016.…”

“…Under photopic conditions, the dog becomes insecure, moves more carefully and appears to be blind (Rubin, 1971a,b;Hurn et al, 2003;Narfström and Petersen-Jones, 2013;Dixon, 2016). Additionally, under light conditions, dogs with cd can be photophobic, and some of them can show miosis (Rubin, 1971a,b;Hurn et al, 2003, Dixon, 2016. Under mesopic and scotopic conditions, the animal acts normally and avoids obstacles, which it hits during daylight hours (Rubin, 1971a,b;Hurn et al, 2003).…”

“…Throughout life, in animals with cd no fundoscopic lesions are observed and pupillary light reflexes (PLR) are normal under all light conditions (Rubin, 1971a,b;Narfström and Petersen-Jones, 2013). The results of electroretinography (ERG) in the course of cd demonstrate normal values for rod-driven responses, while cone-driven responses are markedly reduced or even absent (Aguirre and Rubin, 1975;Andréasson and Tornqvist, 1991;Hurn et al, 2003;Shamir et al, 2010;Genead et al, 2011;Narfström and Petersen-Jones, 2013;Dixon, 2016).…”