TY  - JOUR
SN  - 0146-0404
UR  - http://dx.doi.org/10.1167/iovs.13-12919
JF  - Investigative Ophthalmology & Visual Science
A1  - Stockman, A
A1  - Henning, B
A1  - Michaelides, M
A1  - Moore, AT
A1  - Webster, AR
A1  - Cammack, J
A1  - Ripamonti, C
VL  - 55
SP  - 832
N1  - © The Association for Research in Vision and Ophthalmology, Inc.
IS  - 2
ID  - discovery1417014
N2  - Purpose: We report a psychophysical investigation of five 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 compare 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. Methods: L-cone, S-cone and rod temporal acuity (critical flicker fusion frequency-cff) was measured as a function of target irradiance; L-cone temporal contrast-sensitivity was measured as a function of temporal frequency. Results: Temporal acuity measures reveal 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 is similar in shape to the mean normal function but only after the mean function has been compressed by halving the logarithmic sensitivities. Conclusions: 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.
KW  - Supernormal rod ERG
KW  -  Cone dystrophy
KW  -  Cone-rod dystrophies
KW  -  Flicker sensitivity
KW  -  Critical flicker fusion
KW  -  Temporal acuity
KW  -  Temporal processing
KW  -  KCNV2 gene

TI  - Cone dystrophy with "supernormal" rod ERG: psychophysical testing reveals comparable rod and cone temporal sensitivity losses with no gain in rod function
EP  - 840
Y1  - 2014/02/10/
AV  - public
ER  -