A new study has revealed that the eye's response to blue light could both address the properties of melanopsin, a light-sensitive protein in the eye and help understand seasonal depression.
Geoffrey K. Aguirre, MD, PhD, a behavioral neurologist and associate professor in the department of Neurology said that it was important because they thought melanopsin could be involved in clinical conditions, like too much stimulation of melanopsin produced the feeling of pain from light that is too bright, and not having enough melanopsin stimulation may be part of seasonal affective disorder, in which people could become depressed when they don't have enough light exposure.
Having teased apart the melanopsin and cone responses to blue light, we could study how the eye was involved in these disorders.
They measured the pupil response to stimulation of melanopsin and of short-wave-sensitive (S) cones that were the other blue lights cells that operated in daylight.
The work of the Penn team made it possible to isolate and study the properties of melanopsin in people, separately from the cone cells; therefore, we could now ask what we "saw" with melanopsin.
Already known was that the rods operated in dim light levels and allowed us to see at night. It was the signals from rods and cones that the brain converted into the images that we saw.
Recently, the class of retinal cells that also sensed light known intrinsically as photosensitive ganglion cells, contained the protein melanopsin.
Their complete results were published in the issue of PNAS.