L> The Retina that the human Eye The Retina

The retina is a light-sensitive layer at the earlier of the eye the covers about 65 percent that its inner surface. Photosensitive cells referred to as rods and cones in the retina convert incident light power into signals that are brought to the mind by the optic nerve. In the center of the retina is a little dimple dubbed the fovea or fovea centralis. The is the facility of the eye"s sharpest vision and the ar of most shade perception.

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"A thin layer (about 0.5 come 0.1mm thick) of light receptor cells covers the inner surface ar of the choroid. The focused beam of irradiate is absorbed via electrochemical reaction in this pinkish multilayered structure. The human being eye includes two kinds of photoreceptor cells; rods and also cones. About 125 million of them space intermingled nonuniformly over the retina."(Hecht) The ensemble of rods(each around 0.002 mm in diameter) develops an exceedingly sensitive detector, performing in light as well dim for the cones come respond to. It is unable to distinquish color, and also the pictures it relays are not fine defined.

"In contrast, the ensemble that 6 or 7 million cap (each about 0.006 mm in diameter) deserve to be imagined together a separate, but overlapping, low-speed shade film. The performs in bright light, giving detailed colored views, however is fairly insensitive at short light levels."(Hecht)"

The rods and also cones show up to be pointed away from the light resource they detect. The irradiate strikes the perceptible pigment layer in ~ the ago of the eye and also transfers the details to the nearby rods and cones. The rods and also cones absorb the scattered light from the nearby pigment layer, which renders vision clearer and keeps the sensitive detectors in a an ext protected location. The rods and cones are additionally kept closer to your metabolic energy supply. From the rods and cones, the signal pass through horizontal cells, bipolar cells, amacrine cells and retinal ganglion cells on their way to the retinal highway bring about the optic nerve. (Mammoth)IndexVision conceptsImage formation conceptsReferenceHecht, second Ed.Sec. 5.7Mammoth storage site
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despite the eye receive data native a field ofabout 200 degrees, the acuity over many of thatrange is poor. To kind high resolution images, thelight must autumn on the fovea, and also that limitsthe acute vision angle to about 15 degrees. In low light,this fovea constitutes a second blind spot since it is solely cones which have actually low light sensitivity. In ~ night, to get most acute visionone must change the vision slightly to one side,say 4 to 12 levels so that the light drops onsome rods.

A "dimple ~ above the retina" offers our highest resolution vision.

"Just around at the facility of the retina is a tiny depression native 2.5 come 3 mm in diameterknown as the yellow spot, or macula. There is a tiny rod-free an ar about 0.3mm in diameterat that center, the fovea centralis. (In comparisonthe image of the complete Moon top top the retina is about0.2 mm in diameter.) below the cones space thinner(with diameters of 0.0030mm to 0.0015mm)and more densely pack than all over else in the retina. Because the fovea gives thesharpest and most detailedinformation, the eyeball is repeatedly moving, so that light native the object of primaryinterest drops on this region. ...the rods are multiply linked to nerve fibers, and a solitary such fiber deserve to be caused by any kind of one of around a hundreds rods. By contrast, cones in the fovea room individually linked to nerve fibers. The actual perception of a scene is constructed by the eye-brain device in a continuous analysisof the time-varying retinal image."(Hecht)IndexVision conceptsReferencesHecht, second Ed.Sec. 5.7Williamson & Cummins
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The optic nerve is the cable the nerve fibers through carries the electric signals from the retina to the mind for processing. The suggest of departure of the optic nerve through the retina does no have any kind of rods or cones, and thus produce a "blind spot".


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IndexVision conceptsReferencesHecht, second Ed.Sec. 5.7Williamson & Cummins
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