Page 91 - 84 human physiolofy part-1

Senses

• The visual cortex interprets the signals as images and along with other parts of the brain,
interpret the images to extract form, meaning, memory and context of the images.

Depth Perception

Depth perception is the visual ability to perceive the world in three dimensions. It is a trait
common to many higher animals. Depth perception allows the beholder to accurately gauge the
distance to an object.

Depth perception is often confused with binocular vision, also known as Stereopsis. Depth
perception does rely on binocular vision, but it also uses many other monocular cues.

Diseases, disorders, and age-related changes

There are many diseases, disorders, and age-related changes that may affect the eyes and
surrounding structures. As the eye ages certain changes occur that can be attributed solely to the aging
process. Most of these anatomic and physiologic processes follow a gradual decline. With aging, the
quality of vision worsens due to reasons independent of aging eye diseases. While there are many
changes of significance in the non-diseased eye, the most functionally important changes seem to be a
reduction in pupil size and the loss of accommodation or focusing capability (presbyopia). The area of
the pupil governs the amount of light that can reach the retina. The extent to which the pupil dilates
also decreases with age. Because of the smaller pupil size, older eyes receive much less light at the
retina. In comparison to younger people, it is as though older persons wear medium-density sunglasses
in bright light and extremely dark glasses in dim light. Therefore, for any detailed visually guided tasks
on which performance varies with illumination, older persons require extra lighting.

Color Blindness
Color Blindness or color vision deficiency, in humans is the
inability to perceive differences between some or all colors that
other people can distinguish. It is most often of genetic nature,
but may also occur because of eye, nerve, or brain damage, or
due to exposure to certain chemicals. There are many types of
color blindness. The most common variety are hereditary
(genetic) photoreceptor disorders, but it is also possible to
acquire color blindness through damage to the retina, optic
nerve, or higher brain areas. There is generally no treatment to
cure color deficiencies, however, certain types of tinted filters
and contact lenses may help an individual to distinguish different
colors better.
This image contains a two digit
number similar to the sample above.
Night Blindness Someone who is protanopic might
Also known as Nyctalopia, is a condition making it difficult or not see this number. (GFDL - Zxc,
impossible to see in the dark. It is a symptom of several eye Cyp)
diseases. Night blindness may exist from birth, or be caused by
injury or malnutrition (for example, a lack of vitamin A). The most common cause of nyctalopia
is retinitis pigmentosa, a disorder in which the rod cells in the retina gradually lose their ability to
respond to the light. Patients suffering from this genetic condition have progressive nyctalopia

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