Abstract
Purpose: :
The relative number of long wavelength sensitive (L–) and middle wavelength sensitive (M–) cones varies greatly between individuals. Differences in the relative number of L– and M–cones may also contribute to the gender difference in the ERG response amplitude occasionally reported. A higher relative number of M–cones would increase the Xenon flash Ganzfeld–ERG response amplitude. Higher ERG response amplitudes in females would be consistent with lower L:M–ratios compared to males. The aim of this study was to investigated the relative number of L– and M–cones as well as differences in the early retinal processing by comparing multifocal ERG responses to L– and M–cone isolating stimuli in female and male trichromats.
Methods: :
Multifocal electroretinography and multifocal oscillatory potentials combined with a cone silent substitution technique were used to investigate outer and inner retinal signals (see Albrecht et al. 2002). The L– and M–cone driven signals recorded from 7 female and 7 male trichromats were analysed for the summed response from the whole stimulated area, as well as for a central retinal area of about 25 deg diameter and a peripheral ring centered at about 30 deg eccentricity.
Results: :
We found similar response waveforms for the mfERG responses from central and peripheral retinal areas, but small differences in the mfOP response waveform. The central and peripheral L:M–ratio for the mfERG (central: 2.89 ± 1.19 and 3.46 ± 1.10; peripheral: 2.65 ± 1.04 and 3.57 ± 0.97 for female and male respectively) as well as the mfOPs (central: 2.47 ± 1.11 and 2.04 ± 0.51; peripheral: 2.15 ± 0.56 and 3.07 ± 0.86 for female and male respectively) tended to be lower for female observers than for male observers. L:M–ratios estimated from mfOP recordings are generally lower than those estimated from the mfERG, and the paired correlation between the mfERG and mfOP ratios is significant. However, we found no significant difference in the gain adjustment from outer to inner retina between male and female.
Conclusions: :
While we found no significant difference in the gain adjustment from outer to inner retina between male and female, the L:M–ratio tended to be lower in female observers. A higher number of M–cones, whose spectral sensitivity makes them slightly more sensitive to the spectral distribution of the Xenon–flash compared to the L–cones, is consistent with a higher Ganzfeld response amplitude.
Keywords: electroretinography: non-clinical