Melatonin is a drug that regulates sleep-wake cycle. Some patients using this drug complain from unexplained visual disturbances where as routine visual checking of these patients is normal. Therefore an attempt was made to examine the retinal part of these patients using electroretinographical technique to search for probable toxic effect of Melatonin on Retina.

24 patients were classified in four groups according to the period of Melatonin medication. Flash ERG was used as technique to check the retina of these patients. Latency (m sec) and voltage (µv) of ERG, b wave was recorded for each patient. Obtained values were compared with control group to see differences between two groups.

Melatonin increases the area under b wave ERG which can be measured it, somehow by latency of ERG, b wave. Moreover it was observed that as the doses of Melatonin is increases in a longer period of medication, latency of ERG, b wave is also increases.

It is already reported that broad ERG, b wave is the result of early deep retinal degeneration, so one can conclude that Melatonin produces deep retinal degeneration which can be diagnosed to some extent by measuring the latency of ERG, b wave.