[Two cases of digitalis toxicity with reversible and severe decrease of visual acuity]

We performed electrophysiologic tests on two patients with digitalis toxicity who first had photophobia and xanthopsia and revealed reversible reduced visual acuity and binocular central scotoma.

The patients were a 72-year-old male and a 54-year-old male who had symptoms of digitalis toxicity.

The corrected visual acuity was severely decreased during digitalis toxicity, 0.02 oculus dexter (OD) and 0.1 oculus sinister (OS) in case 1 and 0.04 OD and 0.2 OS in case 2. But visual acuity recovered as the blood levels of digitalis decreased to the normal level and the corrected visual acuity was 0.7 OD and 0.8 OS in case 1 and 0.8 OD and 0.9 OS in case 2. We recorded 30 Hz-flicker electroretinogram (ERG), single flash ERG, photopic ERG, and scotopic ERG when digitalis blood levels were elevated and normal. Decreased amplitudes of 30 Hz-flicker ERG and photopic ERG suggested that photoreceptor function was disturbed at digitalis toxicity and cone dysfunction was more severely disturbed than rod dysfunction.

30 Hz-flicker ERG, as well as electrocardiogram and digitalis blood level, is a relatively convenient and useful measure of digitalis toxicity. It is necessary consiler toxicity when severe visual dysfunction is observed in patients with digitalis therapy.