Monitoring of Patients taking Canthaxanthin and Carotene: An Electroretinographic and Ophthalmological Survey

1 Patients who have taken canthaxanthin and beta-carotene to avert phototoxicity have been monitored by electroretinographic testing. 2 Patients took the compounds only during the summer months, but were monitored for more than 1 year to determine if seasonal changes in the ERG were visible. 3 The characteristic refractile retinal crystals reduced during the winter. 4 The scotopic b-wave amplitude increased during the winter, whether evoked by red or blue flashes. 5 No other ERG parameter altered. 6 Changes noted in 3 and 4 above are reversible. 7 A dose/ERG-amplitude response relationship was established, but no correlation between blood level or total cumulative dose and b-wave amplitude could be found. 8 It is suggested that the Müller cells concentrate canthaxanthin and this is the mechanism which affects the ERG.