Gradient of deficit in cone responses in the incomplete form of congenital stationary night blindness revealed by multifocal electroretinography
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Multifocal electroretinograms were recorded in one case of incomplete form of congenital stationary night blindness. First order kernel revealed reduced cone macular P1 responses with normal implicit time (22.7 nV, 33.3 ms; normal 43.3 ± 8.2 nV, 32.7 ± 0.6 ms) whereas more peripheral responses exhibited low responses of extremely delayed implicit time (5.1 nV, 47.5 ms; normal 7.4 ± 2.1 nV, 32.3 ± 0.8 ms). Responses from the first slice of the second kernel were present in the macular area but absent from the more peripheral areas. In comparison, mfERGs in the complete form of CSNB showed normal amplitude but slightly delayed responses at all eccentricities and normal second kernel responses. Results are discussed in terms of the dichotomy in synaptic transmission between macular and peripheral cones.