Alterations of L- and M-cone driven ERGs in cone and cone–rod dystrophies

Abstract

To study the L- and M-cone pathways and their interactions in patients with cone and cone-rod dystrophies, ERG responses were measured to stimuli which modulated exclusively the L- or the M-cones, or the two simultaneously. The L- and M-cone driven ERG amplitudes were considerably reduced in the patients. The mean phases of the L-cone driven ERGs in the patients lagged those of normals significantly, whereas the mean M-cone driven ERGs were significantly phase advanced resulting in a substantial phase difference between the two ERG responses. These phase changes in the L- and M-cone driven responses in the patients cannot be detected with standard ERG techniques.

Small-field perimetry applied to different types of retinitis pigmentosa: preliminary results

“…These differences are enough to be detected by mean of the statistically significant increment observed in the slope of the fits. This increasing disability of cones with eccentricity is well known in typical RP and has been recently described as a result of a neural reorder occurring in the postreceptoral pathways after the local retinal dysfunction [18][19][20][21]. It is interesting to remark that, as happened with rod response in Figure 2, in Figure 3 slopes of linear fits for TRP3 and CRD patients are very similar to those measured for the control group.…”

Progressive cone dystrophy with deutan genotype and phenotype

“…The ERG signals are 150 ms extracts of 4 s traces that are the averages of 12 runs. Drift components in the electroretinographic responses to the L-and M-cone-isolating stimuli were suppressed by the removal of low frequency components [36] Fig. 5 Threshold contrasts in a "normal" trichromatic subject, a "normal" deuteranope (replotted from Fig.…”

“…[5,10,22,30,36] Genetic studies have revealed numerous genetic subtypes with different modes of genetic transmission (for a review see: http://www.sph.uth.tmc.edu/Retnet/).…”

“…[27,39,45] More severe forms of colour vision deficiency involve the degeneration, dysfunction or absence of at least two types of cone photoreceptors, as observed in patients with incomplete or complete achromatopsia [2,3,[15][16][17]47] or severe cone dystrophies [36].…”

“…(For a review see Scholl [31].) Very recently, a comprehensive study has been performed on a population of patients with cone-and cone-rod dystrophies [36]. In all the studies mentioned it has been found that each of the retinal disorders shows characteristic alterations in certain aspects derived from these cone-driven ERGs.…”