L> The Retina that the human being Eye The Retina

The retina is a light-sensitive layer in ~ the back of the eye the covers around 65 percent that its inner surface. Photosensitive cells referred to as rods and also cones in the retina transform incident light power into signals the are brought to the mind by the optic nerve. In the middle of the retina is a little dimple referred to as the fovea or fovea centralis. It is the facility of the eye"s sharpest vision and also the place of most shade perception.

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"A slim layer (about 0.5 come 0.1mm thick) of irradiate receptor cells covers the inner surface of the choroid. The concentrated beam of irradiate is absorbed via electrochemical reaction in this pinkish multilayered structure. The human eye consists of two type of photoreceptor cells; rods and also cones. About 125 million the them are intermingled nonuniformly end the retina."(Hecht) The ensemble that rods(each about 0.002 mm in diameter) forms an exceedingly perceptible detector, performing in light also dim for the cones come respond to. The is can not to distinquish color, and also the images it relays space not fine defined.

"In contrast, the ensemble of 6 or 7 million cap (each about 0.006 mm in diameter) can be imagined as a separate, but overlapping, low-speed color film. The performs in bright light, giving detailed colored views, but is reasonably insensitive at short light levels."(Hecht)"

The rods and also cones show up to it is in pointed away from the light resource they detect. The irradiate strikes the sensitive pigment layer at the ago of the eye and also transfers the details to the surrounding rods and cones. The rods and cones absorb the scattered irradiate from the adjacent pigment layer, which provides vision clearer and keeps the perceptible detectors in a much more protected location. The rods and also cones are likewise kept closer to their metabolic energy supply. From the rods and also cones, the signal pass v horizontal cells, bipolar cells, amacrine cells and also retinal ganglion cells on their means to the retinal highway bring about the optic nerve. (Mammoth)IndexVision conceptsImage development conceptsReferenceHecht, 2nd Ed.Sec. 5.7Mammoth memory site
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despite the eye receive data native a field ofabout 200 degrees, the acuity over most of thatrange is poor. To form high resolution images, thelight must loss on the fovea, and also that limitsthe acute vision edge to around 15 degrees. In low light,this fovea constitutes a 2nd blind spot because it is specifically cones which have actually low irradiate sensitivity. In ~ night, to get most acute visionone must transition the vision contempt to one side,say 4 to 12 levels so the the light drops onsome rods.

A "dimple ~ above the retina" offers our highest possible 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. Over there is a tiny rod-free region about 0.3mm in diameterat that is center, the fovea centralis. (In comparisonthe image of the complete Moon ~ above the retina is about0.2 mm in diameter.) right here the cones room thinner(with diameters of 0.0030mm come 0.0015mm)and an ext densely packed than everywhere else in the retina. Because the fovea offers thesharpest and also most detailedinformation, the eyeball is repetitively moving, so that light from the object of primaryinterest drops on this region. ...the rods space multiply linked to nerve fibers, and also a solitary such fiber have the right to be activated by any kind of one of around a hundreds rods. Through contrast, cones in the fovea space individually associated to nerve fibers. The yes, really perception the a step is built by the eye-brain system 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 of nerve fibers through carries the electrical signals from the retina to the mind for processing. The suggest of exit of the optic nerve with the retina does no have any rods or cones, and also thus to produce a "blind spot".


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