Selective cone dystrophy with protan genotype.
OBJECTIVE
To determine the functional defects in two male patients with progressive cone dystrophy and hybrid L-M cone pigment genes.


METHODS
Clinical evaluation, standard electroretinography, and electrooculography were performed in two affected patients and two family members. Measurements of spectral sensitivity and transient tritanopia were made in both patients.


RESULTS
In the patients, visual acuity varied between 20/50 and 20/100. The electroretinogram showed reduced flicker responses. When light adapted, a-wave amplitudes were borderline, but b-wave amplitudes were reduced severely. Electroretinography with chromatic stimuli showed a difference between well-preserved responses to green and markedly reduced responses to red stimuli. Spectral sensitivity measurement revealed a lack of L (long-wavelength sensitive; red) cone function and normal function of the S (short-wavelength sensitive; blue) and M (middle-wavelength sensitive; green) cones. Transient tritanopia was abnormal, indicating a severe disturbance of cone-cone interaction.


CONCLUSIONS
Progressive cone dystrophy with predominant dysfunction of L cones exists in both patients. The cone dystrophy may be caused by a rearrangement of the X-chromosome pigment gene array that is associated with the deletion of L-cone sequences and the formation of hybrid L-M cone pigment genes. It cannot be excluded, however, that both patients have protanopia and that cone dystrophy developed because of other causes.
Kellner
U
U
Freie Universität Berlin, Universitätsklinikum Benjamin Franklin, Germany.
Sadowski
B
B
Zrenner
E
E
Foerster
M H
MH
D000328:Adult; D000368:Aged; D003118:Color Perception / Q000502:physiology; D003117:Color Vision Defects / Q000235:genetics / Q000503:physiopathology*; D004247:DNA / Q000032:analysis; D003623:Dark Adaptation; D004585:Electrooculography; D004596:Electroretinography; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D017949:Retinal Cone Photoreceptor Cells / Q000503:physiopathology*; D012162:Retinal Degeneration / Q000503:physiopathology*; D012168:Retinal Pigments / Q000235:genetics*; D012684:Sensory Thresholds / Q000502:physiology; D014792:Visual Acuity
D012168:Retinal Pigments; D004247:DNA