Pronounced abnormalities in the increment threshold curves for the blue and green cone mechanisms only 10 degrees above the fovea, and in some cases in the fovea as well, have been found with a 2.5 degrees stimulus in different genetic types of retinitis pigmentosa. Whenever cone thresholds were abnormal, thresholds determined by the blue cone mechanism (pi1 and pi3) were more elevated than tho...

Variations in the amino acid sequences of the human cone opsins give rise to spectrally variant subtypes of L and M cone pigments even in the population with normal color vision. In vitro mutagenesis studies have shown that a limited number of amino acid substitutions produce shifts in the wavelength sensitivity. Presented here are results comparing electrophysiological measurements of single h...

We have used an adaptive-optics scanning laser ophthalmoscope to image the cone photoreceptor mosaic throughout the central 10 degrees -12 degrees of the retina for four normal subjects. We then constructed montages of the images and processed the montages to determine cone locations. Cone densities range from approximately 10,000 cones/mm2 at 7 degrees to 40,000 cones/mm2 at 1 degrees . The sm...

This paper is devoted to weaken “classical” assumptions and give new arguments to prove existence of sweeping process (associated to the proximal normal cone of sets). Mainly we define the concept of a “directional prox-regularity” and give assumptions about a Banach space to insure the existence of such sweeping process (which permit to generalize the existing results requiring a Hilbertian st...

PURPOSE To describe the clinical findings and genetic analysis in two brothers having a novel retinal disease characterized by an enhanced S-cone phenotype with normal rod function. METHODS Both patients underwent complete ophthalmologic examinations, including fundus photography, electroretinography (ERG), fluorescein angiography and optical coherence tomography (OCT). Mutation analysis of t...

The neural basis for the effects of color and contrast on perceived speed was examined using functional magnetic resonance imaging (fMRI). Responses to S cone (blue-yellow) and L + M cone (luminance) patterns were measured in area V1 and in the motion area MT+. The MT+ responses were quantitatively similar to perceptual speed judgments of color patterns but not to color detection measures. We a...

RESULTS. In the present paper, a model is provided that describes the ERG contrast gains and ERG thresholds in dichromats and color normal trichromats. For the X-chromosome-linked dichromats, the contrast gains of only one cone type (either the L or the M cones) sufficed to describe the ERG thresholds for all stimulus conditions. Data suggest that the M-cone contrast gains of protanopes are lar...

To study human cone phototransduction, the alpha-wave of the ERG was recorded from color normals, dichromats, and patients with retinitis pigmentosa. A model of the activation phase of phototransduction, previously fitted to responses from single rods and the rod alpha-wave, was modified and fitted to the human cone alpha-wave. The modified model fits the cone alpha-wave well and allows questio...

Early studies on Rpe65 knockout mice reported that remaining visual function was attributable to cone function. However, this finding has been challenged more and more as time has passed. Electroretinograms (ERGs) showed that rd12 mice, a spontaneous animal model of RPE65 Leber's congenital amaurosis, had sizeable photopic responses. Unfortunately, the recorded ERG waveform was difficult to int...

Mammalian cones respond to light by closing a cGMP-gated channel via a cascade that includes a heterotrimeric G-protein, cone transducin, comprising Gαt2, Gβ3 and Gγt2 subunits. The function of Gβγ in this cascade has not been examined. Here, we investigate the role of Gβ3 by assessing cone structure and function in Gβ3-null mouse (Gnb3(-/-)). We found that Gβ3 is required for the normal expres...