Vision, the faculty of eyesight, involves two organs - the eyes and the brain.
Vision starts in the retina, the membrane at the back of the eye containing the light-sensitive cells. The rest of the eye is mainly concerned with focussing the right quantity of light onto the retina.
The focussing is done by the cornea in conjunction with
the crystalline lens - the ability to focus being known as accomodation.
By altering the curvature of their surfaces light is refracted to project
a sharp and clear image on the retina. The eye muscles and the extent
of their flexibility is important for correct focussing.
Each of the two eyes receives a slightly different view
of the image; but both images are fused in the brain to deliver a single
interpretation; this stereophonic ability being particularly important
in judging depth.
Inferior Oblique: Upwards, outwards, and anti-clockwise rotation.
Superior Rectus: Upwards, inwards, and clockwise rotation.
Medial Rectus: Inwards.
Inferior Rectus: Downwards, inwards, and anti clockwise.
The most common eye disorders are problems of refraction, such as myopia, hypermetropia and astigmatism. Most of such cases can be corrected by a course of eye exercises, although many prefer to take the 'instant' route of prescription glasses or contact lenses.
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