A form of congenital stationary night blindness with apparent defect of rod phototransduction.

We report findings obtained from an individual with an unusual form of congenital stationary night blindness (CSNB). Although the rhodopsin density difference of this subject was normal, there was no evidence of rod-mediated visual function. Dark-adapted thresholds were cone-mediated, and dark-adapted electroretinograms (ERGs) represented activity of the cone system exclusively. ERG a- and b-waves obtained under light-adapted conditions were normal. The absence of a rod a-wave but the presence of normal rhodopsin density, in combination with normal cone function, indicates that this form of CSNB likely involves a defect of phototransduction that is limited to the rods. In addition, light-adapted b-wave responses to high luminance flashes were larger than dark-adapted responses, whereas a-wave amplitudes were reduced by light adaptation. These ERG results address proposed mechanisms by which light adaptation might enhance cone system responses.

Visual pigments in the human macula assessed by imaging fundus reflectometry.

Multispectral imaging fundus reflectometry and multiple linear regression fitting routines were used to simultaneously assess the spatial distributions of cone visual pigment and rhodopsin in the human macula. As expected from anatomic studies, the cone visual pigment distribution showed a peak in the central fovea and was elliptical, with the broader axis along the horizontal meridian. The rhodopsin distribution showed a minimum in the fovea and the rhodopsin density increased with eccentricity. Both visual pigment distributions showed striking variability among individuals. These data provide visual pigment distributions in the relatively unexplored parafoveal region.