Eye SEEING THE RETINA Borrowing a technique that clarifies images from spy satellites, researchers from the University of Rochester have imaged the distribution of cone cells in the human retina (A. Roorda, D.R. Williams, Nature, 397:520-2, Feb. 11, 1999). The three types of cone cells have photopigments that absorb predominantly short (S), middle (M), or long (L) wavelengths, corresponding to blue/violet, green, and red. Color vision works much like a color television--the brain integrates the individual pixels so that we see a rainbow of colors. S cones were known to form a regular mosaic on the retina, but the M and L cones were difficult to distinguish because their photopigments are similar. The military's adaptive optics approach shines light into the eye and a deformable mirror aligns the reflected beams, correcting for distortion from the lens and cornea. The researchers distinguished between M and L cones because each bleaches different...

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