A keen view of vision: seeing cone cells.At the back of an eye lies the retina, a tissue-paper-like membrane studded with rod and cone cells. Those cells facilitate sight by transforming light energy into electrical signals, which are then sent to the brain. Yet seeing those cells in action is difficult. While scientists study retinal cells removed from eyes donated for research, they have been unable to watch single vision cells at work in living subjects.
Now, Donald Miller, David Williams, and G. Michael Morris, all researchers at the University of Rochester The University of Rochester (UR) is a private, coeducational and nonsectarian research university located in Rochester, New York. The university is one of 62 elected members of the Association of American Universities. (N.Y.), have brought astronomical technology to bear on the retina. Using lasers and charged coupled devices (CCDs) originally designed for stargazing star·gaze
intr.v. star·gazed, star·gaz·ing, star·gaz·es
1. To gaze at the stars.
2. To daydream.
Noun 1. and military applications, they have observed individual, live cone cells with a resolution as small as 3 micrometers, they said this week at a meeting of the Optical Society of America The Optical Society of America (OSA) is a scientific society dedicated to advancing the study of light—optics and photonics—in theory and application, by means of worldwide research, scientific publishing, conferences and exhibitions, partnership with industry, and the in Dallas.
"This resolution is three times greater than the resolution that people have attained so far," says Williams. "It's the highest resolution of photoreceptors Photoreceptors
Specialized nerve cells (rods and cones) in the retina that are responsible for vision.
Mentioned in: Macular Degeneration in living retinas for an image taken outside the eye. This offers a new benchmark for how fine a structure one can see in living retinal tissues. And we're hoping to see more detail in blood vessels Blood vessels
Tubular channels for blood transport, of which there are three principal types: arteries, capillaries, and veins. Only the larger arteries and veins in the body bear distinct names. , receptors, and other types of eye cells."
To obtain such images, the researchers use an argon argon (är`gŏn) [Gr.,=inert], gaseous chemical element; symbol Ar; at. no. 18; at. wt. 39.948; m.p. −189.2°C;; b.p. −185.7°C;; density 1.784 grams per liter at STP; valence 0. laser to bounce a quick flash of light off the retina. They then capture the reflected beam with a CCD CCD
in full charge-coupled device
Semiconductor device in which the individual semiconductor components are connected so that the electrical charge at the output of one device provides the input to the next device. , which funnels the signal into a computer for processing and display. The patient remains awake the whole time.
To improve the instrument's acuity, Williams and his colleagues will incorporate an "adaptive optics" system used by astronomers to help compensate for atmospheric disturbances when viewing light from distant stars. This system has effectively compensated for the optical distortions that arise within an eyeball and obscure a high-resolution view of the retinal cells.
Williams sees two potential uses for this imaging method. One is to help physicians diagnose and chart the course of certain eye diseases -- such as macular degeneration or retinitis pigmentosa -- before disabling symptoms appear. The second possible use is scientific. "We don't yet understand very well how light is absorbed into the pigments of photoreceptors," Williams says. "Maybe by looking at these receptors we can gain some insight into how light passes through the retina's photore-ceptive layer."