Electrophysiologic findings are usually pathologic in patients with chloroquine-induced bull's-eye maculopathy. To avoid maculopathy the daily dosage of chloroquine is estimated not from the actual but from the ideal body weight and should not exceed 3.5 mg/kg/day.
A 59-year-old housewife took a daily dosage of 250 mg chloroquine for her rheumatoid arthritis over a period of 5 years up to a total dose of 450 g. With the height of 160 cm she weighed 68 kg. In 1990, two years after cessation of treatment she complained about blurred vision. Her visual acuity then was 0.8 and fell to 0.3 (right eye) and 0.4 (left eye) in 1996. No vortex keratopathy was observed. A central scotoma was present and fundus-examination showed a typical bull's-eye maculopathy. The mid hypopigmented ring correlated with an increased background fluorescence in the fluorescence-angiogram. Color vision and the retinal nerve fiber photo were normal. In spite of the prominent fundoscopic changes the electrophysiologic examination of this patient (ERG, EOG and pattern-ERG) was normal. The relative smallness of affected retina might explain the normal electrophysiology.
This case of a patient with typical chloroquine-induced bull's-eye maculopathy with normal electrophysiology points to the importance of ophthalmoscopic and visual fields examination in patients under long-term chloroquine treatment. The correct daily dosage of chloroquine below 3.5 mg/kg/day should be given to avoid maculopathy.