VISION. Vision part of the central nervous system which enables organisms to process visual detail, as well as enabling several non-image forming photoresponse functions. It interprets information from visible light to build a representation of the surrounding world.
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part of the central nervous system which enables organisms to process visual detail, as well as enabling several non-image forming photoresponsefunctions. It interprets information from visible light to build a representation of the surrounding world
A. Stimulus : Light Waves
Wavelength > Color
Amplitude > Brightness
Complexity > Saturation
There are essentially four steps to vision.
Thecorneais the transparent, protective outer membrane of the eye.
Theiris, the colored part of the eye, is a ring of muscle.
The iris surrounds an opening called thepupil, which can get bigger or smaller to allow different amounts of light through the lens to the back of the eye. In bright light, the pupil contracts to restrict light intake; in dim light, the pupil expands to increase light intake.
Thelens, which lies behind the pupil and iris, can adjust its shape to focus light from objects that are near or far away. This process is called
Light passing through the cornea, pupil, and lens falls onto the retina at the back of the eye. Theretinais a thin layer of neural tissue. The image that falls on the retina is always upside down.
Rodsare responsible for vision at low light levels (scotopic vision). They do not mediate color vision, and have a low spatial acuity.
Conesare active at higher light levels (photopic vision), are capable of color vision and are responsible for high spatial acuity.
The center of the retina, thefovea, is where vision is sharpest. This explains why people look directly at an object they want to inspect. This causes the image to fall onto the fovea, where vision is clearest.
- this deals with the ability of the retina distinguish differences in stimulation.
- is influenced by three factors:
-process of adjusting the lenses of the eyes to varying distances within the visual field to obtain a clear vision
- this due to the difference in the action between the rods and the cones
Photopia-adaption to light
Scotopia-adaption to dark
Test your eyes
Eye test for myopia and hyperopia
Cover one eye with your hand, without pressing on the lid, and take the test. Cover the other eye and begin the testagain.
Yourdistance visionis deficient if you see the O sharper or blacker, either in the red or the green color.Generally, if you see the O blacker or sharper in the red part, you probably havemyopiaor have a myopic tendency.Conversely, if you see the O blacker or sharper in the green part, you are definitelyhyperopeand have hyperopia.In any case, an eyesight check by an eye care specialist would appear necessary.
Test your eyes
Eye test for
Cover one eye with your hand, without pressing on the lid, and read the test below, letter by letter.
Cover the other eye and begin the test again.
If you have read the test as successfully with the right eye as with the left eye, you probably have good central acuity.
If you do not manage to read all the letters, either with one eye or with two, an eyesight check by an eye care specialist would appear necessary.
Test your eyes
Eye test for AstigmatismCover one eye with your hand, without pressing on the lid, and take the test. Cover the other eye and begin the test again.
If some of the lines appear grayer and some blacker, you probably have anastigmatism- consult your eye care specialist
Test your eyes
TheIshihara testis commonly used to detectDaltonism(color blindness of basic colors: red, blue and green).A distinction is made between:
Tritanopes cannot be identified using aIshihara testbut instead requires a 100 Hue test, which needs to be carried out by youreye care specialist.
Rarer are people with complete color blindness, who only perceive levels of gray. They are said to suffer from achromatopsia.What can you see inside each of these circles?
- originated by the famous English Scientist Sir Isaac Newton.
The wave lenghts to which the human eye is sensitive to range from 780-380 m.u.
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