Cone receptor sensitivity is altered in form deprivation myopia in the chicken.
OBJECTIVE
The effect of form deprivation myopia (FDM) on cone photoreceptor function was investigated.


METHODS
Photopic electroretinogram (ERG) a-waves were recorded from control and form-deprived eyes of chickens. Cone-generated P3 responses were derived from the leading edge of ERG a-waves using an analytical expression derived from a quantitative model of phototransduction. The parameters obtained were the maximum cone P3 response (RmaxP3), sensitivity (S), and delay (t(d)).


RESULTS
P3 response sensitivity is significantly higher in form-deprived eyes, at lower retinal irradiances. At higher flash intensities, in form-deprived eyes, P3 response sensitivity declines at a significantly greater rate, per unit increase in retinal irradiance, than in control eyes. Visual deprivation does not significantly affect RmaxP3 or t(d).


CONCLUSIONS
Hypotheses to explain the altered cone photoreceptor sensitivity in form-deprived eyes are proposed. Changes in the biochemistry of phototransduction, or intrinsic geometric and physical attributes of photoreceptors or their waveguide modal properties, could account for the findings.
Westbrook
A M
AM
University of New South Wales, Kensington, Australia.
Crewther
D P
DP
Crewther
S G
SG
D000818:Animals; D002645:Chickens; D004195:Disease Models, Animal; D004596:Electroretinography; D005260:Female; D008297:Male; D009216:Myopia / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D010775:Photic Stimulation; D017949:Retinal Cone Photoreceptor Cells / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D012683:Sensory Deprivation; D014463:Ultrasonography; D014785:Vision, Ocular / Q000502:physiology*