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Rola Ba-Abbad, Andrew Webster, Anthony T Moore, Michel Michaelides, Bart Peter Leroy, Andrew Stockman; Characterisation of temporal vision in congenital stationary night blindness. Invest. Ophthalmol. Vis. Sci. 2016;57(12):No Pagination Specified. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To assess temporal acuity and contrast sensitivity in subjects with molecularly confirmed congenital stationary night blindness (CSNB) and to associate functional losses with the molecular pathology.
L-cone temporal acuity (critical fusion frequency or CFF) as a function of retinal irradiance, and L-cone temporal contrast sensitivity as a function of frequency (TCSF) were measured using standard methods in probands with CSNB and in ten controls. A rapid-on or rapid-off sawtooth modulated, 650-nm stimulus, with a diameter of 4°, was produced with a Maxwellian-view system. Differences in CFF and TCSF between probands and controls were modelled.
Six unrelated probands with complete CSNB and mutations in NYX(3), GRM6(2), TRPM1(1), and 3 males with incomplete CSNB (CACNA1F mutations) participated. Despite some loss in CFF, the CFF slope was normal in 2 NYX probands, but reduced in the 3rd. The TCSF was normal in 1 NYX proband, but showed an early peak at 4 Hz and mild loss of sensitivity at higher frequencies in the others. GRM6 probands showed significant reduction of the CFF and its slope, with profoundly reduced TCSF at all frequencies. The CFF was normal in the TRPM1 proband, but the TCSF showed sensitivity losses below 20 Hz that were less at higher frequencies. The CFF in CACNA1F probands was variable: two probands had a plateau or reduction of the CFF at high irradiance levels, the third proband had profound reduction of the CFF and its slope. The TCSF showed variable degrees of sensitivity loss that worsened at high frequencies. No differences were found in the CFFs or TCSFs for rapid-on and rapid-off waveforms.
CSNB subjects show a broad range of temporal acuity and contrast sensitivity losses. The differences between the TCSF function in controls and probands can be modelled as a simple low-pass filter. Temporal acuity and contrast sensitivity data suggest that the severity of loss is genotype-dependent, with the GRM6-related phenotype being the most severe. In the absence of other pathologies, CSNB offers an example of a non-progressive disorder of the first retinal synapse not confounded by cell death and inner retinal remodelling. Surprisingly, given the OFF pathway preservation in complete CSNB, there is no difference in sensitivity for rapid-on and rapid-off stimuli.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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