Abstract
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.
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