from The American Heritage® Dictionary of the English Language, 5th Edition.
- noun A delicate, multilayered, light-sensitive membrane lining the inner eyeball and connected by the optic nerve to the brain.
from The Century Dictionary.
- noun The innermost and chiefly nervous coat of the posterior part of the eyeball, between the choroid coat and the vitreous humor.
from the GNU version of the Collaborative International Dictionary of English.
- noun (Anat.) The delicate membrane by which the back part of the globe of the eye is lined, and in which the fibers of the optic nerve terminate. See
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun anatomy The thin
layerof cellsat the back of the eyeballwhere lightis convertedinto neural signalssent to the brain.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- noun the innermost light-sensitive membrane covering the back wall of the eyeball; it is continuous with the optic nerve
from The American Heritage® Dictionary of the English Language, 4th Edition
from Wiktionary, Creative Commons Attribution/Share-Alike License
The clarity of the images produced on the retina is a factor which determines the power of vision.
The retina is a thin layer of nerve tissue that coats the back of the eye and enables the eye to see.
"Inverted retina" is part of visual system that works very well in humans and birds, so on what basis does Johnson call this "bad design".
Using an intact retina from a guinea pig, the researchers recorded spikes of electrical impulses from ganglion cells and calculated the human retina can transmit data at roughly 10 million bits per second.
Our eyes (retina is behind the optic nerve, not intelligently in front of it like exists in other life forms), the bones are an engineering disaster, the appendix has no function, the coccyx is a tail bone (we have no tail), and we possess pseudo genes (genes that exist but do not function).
I would argue that the design for the retina is in fact the best choice, given the restraints of its design and past evolutionary choices/routes.
Hubel and Wiesel were also able to show by their experiments that the ability of the cells in the visual cortex to interpret the code of the impulse message from the retina is developed directly after birth.
The pupil, or aperture, through which rays pass to the retina, is the tenderest part of the eye; the member which we most sedulously guard from hurt as being the dearest of our members; the one which feels most acutely the slightest injury, and the loss of which is irreparable.
I had already been receiving laser treatments for diabetic retinopathy for a couple of years, so I called my retina specialist later that morning, then lived through an agonizing 24 hours until I could see him the following day.
In a preliminary study, Australian researchers examined the photographs of the light-sensitive part of the eye called the retina in 13 people with Alzheimer's, 13 with mild cognitive impairment and 110 healthy individuals.