Abnormal retinal function associated with isotretinoin therapy for acne
R. G. Weleber, S. T. Denman, J. M. Hanifin and W. J. Cunningham
Three of 50 patients treated with isotretinoin (1 mg/kg/day) for cystic
acne complained of poor night vision and/or excessive glare sensitivity.
While still receiving the drug or shortly thereafter, two patients were
found to have abnormal dark-adaptation curves, with elevations of either
cone or rod thresholds, or both. Two patients had abnormal
electroretinograms (ERGs). One had a mildly abnormal electro-oculogram. The
dark-adaptation curves were normal for one patient several months after
isotretinoin therapy was discontinued. Two patients had elevated cone
thresholds at least one year later. Six months following cessation of
therapy, the ERG was still abnormal for one patient, but continued
improvement was evident at 25 months; for the second patient, the ERG was
normal at one year. Analysis of Naka-Rushton parameters for the ERG
scotopic b-wave stimulus-response curves indicated response compression for
two patients, as evidenced by a reduction in the maximum response. For one
patient, the half-saturation constant was elevated 0.7 log units,
suggesting reduction of retinal sensitivity, perhaps from decrease in
retinal photopigment concentration. We suspect that isotretinoin may
complete for normal retinol binding sites on cell surfaces or transport
molecules. A prospective study is currently underway to determine if a
clinically measurable adverse effect on retinal function is seen with
greater frequency.
