The retina uses cones and rods as photoreceptors, or light detectors, for vision. In addition to this the retina also contains non-visual photoreceptors for non-visual tasks. These tasks involve the regulation of sleep/wake behavior, control of pupillary constriction, and the timing of physiological events within the retina itself. It is this last aspect I am primarily interested in. Molecular events within cells and between cells in the retina are coordinated based on the time of day. The coordination of this timing likely contributes to the retina’s response to photo-damage and long term health. We have identified the unique photoreceptors which allow for the cells within the retina to synchronize to sunlight. We were surprised that these photoreceptors were completely distinct from visual photoreceptors, like an extra eye for the retina itself.
We are next trying to determine the breadth of the role this timing has on ocular health. The identification of this photoreceptor, Opn5, is a key step in understanding how the diverse cells within the retina coordinate their metabolic and dynamic molecular events to predict times of high light exposure. An important next step is to understand the way that the signal is transmitted among the cells. The retina is a remarkably heterogeneous tissue. Many cells use specific transmitters to communicate with other cells in their circuit, like many people in a city speaking in different languages only to their own groups. This signal that Opn5 cells transmit seems to be a language that all of the retinal cells can interpret.