Andrew Hartwick, Ph.D.

Assistant Professor, College of Optometry


Current Research Description

The visual signal travels from the eye to the brain along retinal ganglion cell (RGC) axons, and the anatomy and physiology of these retinal output neurons are the focus of research in my lab. A small group of RGCs in the inner mammalian retina express the photopigment melanopsin and can respond directly to light. These neurons provide information regarding environmental light levels (irradiance) to the brain centers that regulate circadian rhythms (daily rhythms of physiology and behavior) and the size of the pupil of the eye. The mechanisms underlying the intrinsic light responses of these cells have yet to be fully elucidated, and we are currently investigating how these photoreceptors are able to convert captured light photons into an electrical signal. In addition, we are investigating the contribution of melanopsin-containing RGCs to light-evoked pupil constriction. A long-range goal of the lab is to investigate the effect of glaucoma on retinal irradiance coding, and determine whether defects in this pathway are clinically detectable prior to those associated with vision.

Projects that are currently ongoing in the lab involve investigations on: 1) the photochemical cycle (chromophore bleaching and regeneration) of melanopsin in light-sensitive RGCs; 2) new testing strategies for isolating specific components of the pupillary light reflex that are mediated by melanopsin-containing RGCs (as opposed to rod- or cone-driven components); and 3) the circadian rhythm of intraocular pressure in rats.

Areas of Expertise
  • Systems Neuroscience
  • PhD: Dalhousie University
  • Postdoctoral Training: Colorado State University, Dr. Gary Pickard

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