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Monday, July 25, 2011

Visualizing rods and cones




Rods and cones are light sensing cells that allow us to see.  Now thanks to innovations led by Alfredo Dubra of the University of Rochester, we can see the rods and cones



Caption: The image on the left shows the smallest cones at the center of the retina, (the fovea). Whenever we direct our gaze at something, for example to read, the image of what we are looking at is formed over these very important cones. The image on the right shows a more eccentric retinal location, in which the large bright dots with a dark ring around them are cones, and the surrounding (and far more abundant) smaller spots are rods.
Credit: University of Rochester/Biomedical Optics Express

The researchers used ‘adaptive optics’ a tool developed by astronomers to make distortion free images of stars.  In astronomy, a bright point, either a nearby star or focused laser, is used as a reference.  The adaptive optic system then uses a deformable mirror to compensate for atmospheric distortions, effectively eliminating the twinkling effect of stars.  This substantially increases a telescope’s resolution.  In the same way, using mirrors to compensate for the distortion created as light passes through the front of the eye increases the resolution of the ophthalmoscope to the point where individual rod cells can be discerned.

Dubra and his colleagues successfully collected images of rods and cones from the retinas of nine healthy people. You can see his explanation below:


It’s not hard to come up with medical uses for this new imaging ability.  Not only could the effects of eye diseases be seen in real time, so could the effects of drugs or other treatments.