RT Journal Article
A1 Stockman, Andrew
A1 Henning, G. Bruce
A1 Michaelides, Michel
A1 Moore, Anthony T.
A1 Webster, Andrew R.
A1 Cammack, Jocelyn
A1 Ripamonti, Caterina
T1 Cone Dystrophy With “Supernormal” Rod ERG: Psychophysical Testing Shows Comparable Rod and Cone Temporal Sensitivity Losses With No Gain in Rod Function
JF Investigative Ophthalmology & Visual Science
JO Invest. Ophthalmol. Vis. Sci.
YR 2014
DO 10.1167/iovs.13-12919
VO 55
IS 2
SP 832
OP 840
SN 1552-5783
AB    We report a psychophysical investigation of 5 observers with the retinal disorder “cone dystrophy with supernormal rod ERG,” caused by mutations in the gene KCNV2 that encodes a voltage-gated potassium channel found in rod and cone photoreceptors. We compared losses for rod- and for cone-mediated vision to further investigate the disorder and to assess whether the supernormal ERG is associated with any visual benefit.    L-cone, S-cone, and rod temporal acuity (critical flicker fusion frequency) were measured as a function of target irradiance; L-cone temporal contrast sensitivity was measured as a function of temporal frequency.    Temporal acuity measures revealed that losses for vision mediated by rods, S-cones, and L-cones are roughly equivalent. Further, the gain in rod function implied by the supernormal ERG provides no apparent benefit to near-threshold rod-mediated visual performance. The L-cone temporal contrast sensitivity function in affected observers was similar in shape to the mean normal function but only after the mean function was compressed by halving the logarithmic sensitivities.    The name of this disorder is potentially misleading because the comparable losses found across rod and cone vision suggest that the disorder is a generalized cone-rod dystrophy. Temporal acuity and temporal contrast sensitivity measures are broadly consistent with the defect in the voltage-gated potassium channel producing a nonlinear distortion of the photoreceptor response but after otherwise normal transduction processes.  
RD 4/19/2021
UL https://doi.org/10.1167/iovs.13-12919