Dr. Zeitzer is a circadian physiologist specializing in the understanding of the impact of light on circadian rhythms and other aspects of non-image forming light perception.

He examines the manner in which humans respond to light and ways to manipulate this responsiveness, with direct application to jet lag, shift work, and altered sleep timing in teens. Dr. Zeitzer has also pioneered the use of actigraphy in the determination of epiphenomenal markers of psychiatric disorders.