Word: retinas
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...smaller facets. Each focuses on a handful of photo receptors and produces only a single point in the insect's visual field. But the researchers, reporting last week in the journal Science, found that each of X. peckii's 100 eyelets is really a complete eye with its own retina, consisting of some 100 receptors, that samples a "chunk" of the visual field. These neighboring chunks, when combined in the insect's brain, produce an image with exceptionally high resolution...
...bright the incoming light is, the pupil grows wider or narrower, much like the adjustable aperture of a camera. The light then passes through the lens, which lies directly behind the iris and changes shape as needed--curving or flattening--to help focus the image onto the retina, the light-sensitive tissue at the back of the eyeball that converts the light into electrical signals. From there, the optic nerve sends these impulses to the brain's optic centers, which create the picture in your mind...
...happens, the eye's lens provides just a third of the eye's focusing power. The rest comes from the cornea, which acts like a second lens to help focus light onto the retina. If you're nearsighted, or myopic, your eye produces clear images of nearby objects or people. But light from distant sources is focused on a point somewhere in front of your retina--either because the curve of your cornea is too steep relative to the length of your eyeball, or the eyeball is too long relative to the corneal curve. If you're farsighted, or hyperopic...
...tomboy, and my father spent countless hours playing catch with me. But he never expected that there would be organized softball for girls. Of course, there was a part of him that overworried about my infrastructure. Girls have babies, after all! When my brother got a detached retina playing tackle, my parents didn't blanch. One day I came home with a bloody nose, and I thought my father was going to pass...
Theoretically, two other problems could arise. The first: tumors in blood vessels. So far, none of the animals tested over seven years has developed abnormal growths. The second: impaired vision, the hypothetical result of too much of the protein, especially in diabetics, promoting excessive blood-vessel growth in the retina. No problem...