Improvement of scotopic electroretinograms and night blindness with recovery of serum zinc levels.

BACKGROUND

We sought to determine the cause of reduced scotopic and photopic electroretinograms (ERGs) and night blindness in a 46-year-old man with liver dysfunction but no history of alcoholism.

CASE: A 46-year-old Japanese man with a complaint of visual difficulties in dim light for 1 month.

OBSERVATIONS: By electrophysiological investigation, the patient was found to have low levels of serum zinc and vitamin A on admission. The rod b wave was unrecordable, and the bright-flash ERGs were reduced, with the a wave > b wave. The amplitudes of the cone and 30-Hz flicker responses were also reduced, and their implicit times were prolonged. Three weeks after admission, the patient's serum zinc level recovered to normal levels, but his serum vitamin A level was still low. The symptoms of night blindness were gone, and the rod ERGs and single bright-flash responses were within normal limits. However, the cone ERGs and 30-Hz flicker responses were still depressed.

CONCLUSIONS

The recovery of scotopic function together with the recovery of zinc but not vitamin A levels suggests that the ERG changes were most likely related to low zinc levels.