Other Vision

Binocular vision is vision in which both eyes are used together. The word binocular comes from two Latin roots, bin for two, and oculus for eye. Having two eyes confers at least four advantages over having one. First, it gives a creature a spare eye in case one is damaged. more...

Home
Bath & Body
Dental Care
Dieting/ Slimming
Fragrances
Hair Care
Hair Removal
Health Care
Make-Up/ Cosmetics
Massage
Mobility, Disability &...
Nails/ Manicure/ Pedicure
Natural/ Alternative...
Other Health & Beauty
Over-the-Counter Medicine
Skin/ Face Care
Tanning/ Sun Care
Tattoos/ Body Art
Vision/ Glasses/ Lenses
Contact Lens Solutions/...
Eye Baths
Eye Cream
Eye Gel
Glasses
Glasses Cases
Other Vision
Vitamins/ Supplements

Second, it gives a wider field of view. For example, a human has a horizontal field of view with one eye of about 150 degrees and with two eyes of about 180 degrees. Third, it gives binocular summation in which the ability to detect faint objects is enhanced. Fourth it can give stereopsis in which parallax provided by the two eyes' different positions on the head give precise depth perception. Such binocular vision is usually accompanied by singleness of vision or binocular fusion, in which a single image is seen despite each eye's having its own image of any object.

Other phenomena of binocular vision include utrocular discrimination, eye dominance, allelotropia, and binocular rivalry.

Fields of view and eye movements

Some animals, usually prey animals, have their two eyes positioned on opposite sides of their heads to give the widest possible field of view. In such animals, the eyes often move independently to increase the field of view. Even without moving their eyes, some birds have a 360-degree field of view.

Other animals, usually predatory animals, have their two eyes positioned on the front of their heads, thereby reducing field of view in favour of stereopsis. In such animals, the eyes usually move together. When the eyes move laterally, in the same direction, this is called a version. When the eyes move in opposite directions, to an object closer than where the eyes are pointing or farther than where the eyes are pointing, this is called a vergence. When the eyes move in, it is a convergence eye movement; when the eyes move out, it is a divergence eye movement.

Some animals (including some humans, notably exotropes) use both of the above strategies. A starling, for example, has laterally placed eyes to cover a wide field of view, but can also move them together to point to the front so their fields overlap giving stereopsis. A remarkable example is the chameleon, whose eyes appear to be mounted on turrets, each moving independently of the other, up or down, left or right. Nevertheless, the chameleon can bring both of its eyes to bear on a single object when it is hunting, showing vergence and stereopsis.

Binocular summation

Binocular summation means that the detection threshold for a stimulus is lower with two eyes than with one. There are two forms. First, when trying to detect a faint signal, there is a statistical advantage of using two detectors over using one. Mathematically, the advantage is equal to the square root of 2, about 1.41. Second, when some cells in the visual cortex receive input from both eyes simultaneously, they show binocular facilitation, a greater level of activity than the sum of the two activities evoked separately from each eye. Any advantage in using two eyes in detection task over 1.41 is credited to this sort of mechanism, dubbed neural summation.

Read more at Wikipedia.org