How The Eye Works

A human eye gives the sharpest vision when it is perfectly spherical. Distortion occurs when either the eyeball or the cornea are slightly out of round This causes a range of vision conditions known as astigmatism, myopia, or hyperopia.

The coloured ring of the eye, the iris, controls the amount of light allowed into the eye. It automatically opens (dilates) and closes (contracts) the pupil when the light around you changes. Light travels through a small hole, the pupil. Muscles inside the eye automatically change the shape of the lens to focus an upside-down image on the light-sensitive cells of the retina. This delicate sheet of light-sensitive nerve tissue collects and transmits images to the brain via the optic nerve.