Analysis Tools
vision/eye
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• at 3 weeks of age, homozygotes exhibit normal-sized eyes and have retinas with a typical layered structure of three nuclear layers, similar to those seen in wild-type mice
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• homozygotes exhibit only weak light-adapted (photopic) cone-driven ERG responses relative to control littermates, with a >60% reduction in b-wave amplitude (a measure of "on" cone bipolar cell function) at both 45 ms and 200 ms after the flash, as well as smaller a-wave amplitude at 12 ms after the flash
• ERG reductions occurr both for the lower stimulus energies, where the wavelength is such that only the M cones are stimulated (lambdamax = 514 nm), and for the two highest energies (3.0 and 3.5 log scot td), where a xenon flash elicits responses from the UV cones as well
• reduction in a-waves is most likely due to the dysfunction of "off" cone bipolar cells, although cone photoreceptor abnormalities cannot be excluded
• in contrast to the photopic ERG, the scotopic ERG of homozygous mutant mice is comparable to that of wild-type mice in response to both strong flashes that saturate the a-wave and weak flashes that elicit responses dominated by rod bipolar cell activity
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