Familial macular cone dystrophy: diagnostic value of multifocal ERG and two-color threshold perimetry.
BACKGROUND
It is difficult to detect receptor dysfunction in patients with marked bilateral visual loss but only mild morphological alterations of the fundus.


METHODS
Two patients, father and son, with visual acuity loss to 20/100 were examined. Using the multifocal ERG, 61 local cone ERGs from each eye were derived from the central visual field. The dark-adapted two-color threshold perimetry using stimuli of 500 nm and 656 nm for rod and cone function was investigated along the horizontal meridian of the visual field.


RESULTS
In the multifocal ERG of both patients a macular response was absent. From eccentricity at and anterior to 5 degrees, good multifocal cone activity was recorded. Cone thresholds were markedly diminished in the macula. The rod thresholds were borderline in the father and normal in the son.


CONCLUSIONS
Multifocal ERG is a novel technique, very well suited to reveal the topography of cone function. Using two-color threshold perimetry affords an opportunity to differentiate between rod and cone functional defects. Both together helped to establish the diagnosis of macular cone dystrophy in the present family.
Kretschmann
U
U
University Eye Hospital, Department for Pathophysiology of Vision and Neuro-Ophthalmology, Tübingen, Germany.
Stilling
R
R
Rüther
K
K
Zrenner
E
E
D000328:Adult; D003623:Dark Adaptation; D003937:Diagnosis, Differential; D004596:Electroretinography; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008268:Macular Degeneration / Q000175:diagnosis* / Q000235:genetics / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009679:Nuclear Family; D017949:Retinal Cone Photoreceptor Cells / Q000473:pathology* / Q000503:physiopathology; D014792:Visual Acuity; D058609:Visual Field Tests; D014794:Visual Fields / Q000502:physiology