Binocular vision is vision in which
both eyes are used together. The word binocular comes from two Latin roots,
bini for double, 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. Second, it gives a wider field of view. For example, humans have a
maximum horizontal field of view of approximately 200 degrees with two eyes,
approximately 120 degrees of which makes up the binocular field of view (seen
by both eyes) flanked by two uniocular fields (seen by only one eye) of
approximately 40 degrees. Third, it gives binocular summation in which the
ability to detect faint objects is enhanced.Fourth it can give stereo-psis 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. Orthoptists are eye-care professionals who fix binocular
vision problems.
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