Functional Anatomy of the Eye
The eye functions much like a camera. The front components help focus light onto a “film” called the retina. Differences in light intensity and color cause chemical changes within the retina. As many as a million nerve fibers carry the impulses from these chemical changes to the brain via the optic nerve. These impulses are integrated both along the nerve pathway and the occipital cortex of the brain, where a visual image is interpreted. Damage to any of these parts or changes in any of these functions can result in partial or total vision loss.
Parts of the Eye
Cornea – The transparent covering at the front of the eye which helps protect the inner parts of the eye. It is a part of the eye’s focusing system. Any change in the regularity of the corneal structure disrupts the transmission of light. This disruption can be due to dryness, accident, degeneration or infection.
Iris – A colored circular membrane suspended behind the cornea and immediately in front of the lens. The iris regulates the amount of light entering the eye by adjusting the size of the pupil.
Lens – The transparent tissue behind the iris which bends light rays and focuses them on the retina. The lens contributes to the adjustments in focus (accommodation) of the eye. Changes that occur in the lens include loss of flexibility, which is normal with aging and opacification (cataracts).
Macula – The central area of the retina. It is the most sensitive area of the retina and it is responsible for fine focusing or detail vision for reading.
Optic Nerve – The nerve at the back of the eye that carries visual impulses from the retina to the brain. The area where the nerve connects with the retina is known as the optic disc.
Pupil – The adjustable opening at the center of the iris that allows light to enter the eye.
Retina – A thin lining at the back of the eye that transmits visual impulses via the optic nerve to the brain. The retina receives its nourishment from blood vessels on its surface and underneath it. Any changes in the supply of blood results in retinal damage and permanent loss of vision. Retinal disorders are the leading cause of blindness in the United States. Retinal disorders include macular degeneration, diabetic retinopathy, and retinal detachment.
Vitreous Gel – The clear gel behind the lens which fills the back of the eye. Loss of transparency can blur or distort vision.