[Electroretinogram "b" wave varies with the posology of the antimalarial treatment]

The electroretinogram (ERG) is currently, together with the central visual field test, color vision test and electroculogram (EOG), an examination dedicated to prevent retinopathy due to hydroxychloroquine (HCQ) or chloroquine (CQ) intoxication.

Thirty-two patients on treatment with HCQ were studied. Each patient had underwent a complete clinical ophthalmological examination and a set of paraclinical examinations including at least an ERG. All the patients were requested to decrease or stop their HCQ treatment. Following this change, a second ERG was recorded for each patient. The ERGs before and after stopping HCQ treatment were compared. We noted a statistically significant increase in the amplitude of "b" wave of the ERG, following after decrease or discontinuation of HCQ treatment.

This study has demonstrated the ERG "b" wave sensitivity due to the variation of HCQ consumption. The amplitude and the culmination time of the ERG "b" wave are important parameters to monitor during long term treatment with HCQ. A decrease of the "b" wave amplitude, coupled with an increase of its culmination time in a patient on long term HCQ treatment showing for the same daily dose, shall be a sign of alert, imposing the performance of additional visual functional tests and leading a decrease or a discontinuation of the treatment with HCQ. The ERG is an objective examination, which needs almost no participation from the patient. Its usefulness has been demonstrated, for the prevention of retinopathy due to hydroxychloroquine or chloroquine intoxication in condition that successive ERGs of the same patient are precisely compared.