L- and M-cone-driven electroretinograms in Stargardt's macular dystrophy-fundus flavimaculatus.
OBJECTIVE
To study the dynamics of the long (L)- and middle (M)-wavelength-sensitive cone-driven pathways and their interactions in patients with Stargardt's macular dystrophy-fundus flavimaculatus (SMD-FF) and to correlate them with other clinical parameters and individual genotypes.


METHODS
Forty-seven patients with SMD-FF participated in the study. In addition to standard 30-Hz flicker electroretinograms (30-Hz fERG), ERG responses were measured to stimuli that modulated exclusively the L or the M cones (L/M cones) or the two simultaneously. Blood samples were screened for mutations in the 50 exons of the ABCA4 gene.


RESULTS
Patients with SMD-FF did not show a decrease in the mean L/M-cone-driven ERG sensitivity, but there was a significant increase in the interindividual variability. The mean L-/M-cone weighting ratio was normal. However, the L-cone-driven ERG was significantly phase delayed, whereas the M-cone-driven ERG was significantly phase advanced. These phase changes were significantly correlated with disease duration. The amplitude and implicit time of the standard 30-Hz fERG both correlated significantly with the L/M-cone-driven ERG sensitivity and with the phase difference between the L/M-cone-driven ERGs, indicating the complex origin of the standard 30-Hz fERG. Probable disease-associated mutations in the ABCA4 gene were found in 40 of 45 patients, suggesting that they form a genetically fairly uniform SMD-FF study group. There was no correlation between the genotype and the L/M-cone-driven ERGS:


CONCLUSIONS
The changes in L/M-cone-driven ERG sensitivity and phase possibly represent two independent disease processes. The phase changes are similar to those found in patients with retinitis pigmentosa and possibly are a general feature of retinal dystrophies.
Scholl
H P
HP
Department of Experimental Ophthalmology, University Eye Hospital, Röntgenweg 11, 72076 Tübingen, Germany.
Kremers
J
J
Vonthein
R
R
White
K
K
Weber
B H
BH
D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D000293:Adolescent; D000328:Adult; D003119:Color Perception Tests; D004252:DNA Mutational Analysis; D004596:Electroretinography; D005260:Female; D005654:Fundus Oculi; D005838:Genotype; D006801:Humans; D008268:Macular Degeneration / Q000235:genetics / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D017949:Retinal Cone Photoreceptor Cells / Q000503:physiopathology*; D014792:Visual Acuity
D018528:ATP-Binding Cassette Transporters