Macular dystrophy with protan genotype and phenotype studied with cone type specific ERGs.
OBJECTIVE
To determine the L- and M-cone driven ERG responses in a male patient with macular dystrophy and a protan phenotype.


METHODS
We measured large field ERG thresholds to stimuli which modulated exclusively the L- or the M-cones or the two in various combinations (both in-phase and in counterphase). In none of the stimuli, the S-cones were modulated. Additionally, standard and multifocal ERGs were measured. Analysis of the L- and M-cone pigment genes was performed by means of PCR, RFLP analysis and DNA sequencing techniques.


RESULTS
Macular dystrophy was revealed by the markedly abnormal multifocal ERGs in presence of near normal standard ERGs. The large field ERG responses were exclusively driven by the M-cones with enlarged thresholds when compared with otherwise normal protanopes. In addition, the M-cone driven ERG response phases were abnormal. Pigment gene analysis confirmed a protan genotype with the presence of a single 5'red/3'green hybrid pigment gene.


CONCLUSIONS
Our novel stimulus technique allows a reliable analysis of the separate cone pathways even in cases with macular dysfunction. The increased thresholds and the abnormal phase behavior of the M-cone driven ERGs reflect altered mechanisms of the retinal physiology in this patient. The data strongly suggest that the macular dystrophy and the protanopia have independent origins.
Scholl
H P
HP
Laboratories of Electrophysiology, Department of Experimental Ophthalmology, University Eye Hospital Tübingen, Germany. hendrik.scholl@uni-tuebingen.de
Kremers
J
J
Wissinger
B
B
D000328:Adult; D003117:Color Vision Defects / Q000235:genetics / Q000503:physiopathology*; D017931:DNA Primers; D004596:Electroretinography; D005838:Genotype; D006801:Humans; D008268:Macular Degeneration / Q000235:genetics / Q000503:physiopathology*; D008297:Male; D010641:Phenotype; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D017949:Retinal Cone Photoreceptor Cells / Q000503:physiopathology*; D012168:Retinal Pigments / Q000235:genetics*; D017422:Sequence Analysis, DNA
D017931:DNA Primers; D012168:Retinal Pigments