INTRODUCTION TO ANATOMY AND PHYSIOLOGY

Functions of the Eye

The eyeball itself is a highly complex organ.

Listed in the picture above are some of the primary elements and listed below are their functions.

CONJUNCTIVA– This is the mucous membrane that lines the inner surface of the eyelids.

CORNEA – The transparent, domed portion of the eyeball that covers the iris and pupil. It acts like a window, letting light into the eye.

IRIS– The iris is a muscular diaphragm that is suspended in the front lens of the eye. It is deeply pigmented and designed to exclude light, except through the pupil.

LENS– Located behind the pupil, the lens focuses incoming light rays onto the retina.

MACULA– Lying near the centre of the retina, this area is made up almost entirely of retinal cones, these are responsible for colour sensation.

OPTIC NERVE– This is the sensory nerve that carries electrical impulses from visual stimuli received by the retina. The end destination is the brain.

PUPIL– Located in the iris, the pupil is designed to let light pass through to the lens of the eye.

RETINA– This is a layer of nervous tissue covering the back of the eyeball. Light hits the tissue and initiates an electrochemical reaction in which electrical impulses are transmitted to the brain.

VITREOUS BODY– This is the gelatinous mass that occupies the space between the lens and the retina, its composed of 99% water.

 

VISION

Our eyes form a very intricate optical system (sometimes likened to the operation of a camera) our vision follows the following steps, so we can clearly see images that surround us:

  • Light enters the eye via the cornea (this performs the task of focusing)
  • The light travels through aqueous fluid and then through the pupil
  • The pupil changes size according to the amount of light entering the eye (this occurs when the muscles in the iris constrict or relax)
  • Light rays then reach the retina which creates an “upside down” image.
  • The Retina then sends a signal to the brain via the optic nerve by means of an electrical impulse where it is converted to an upright image.

 

Vision is affected if the cornea becomes thickened and loses its transparency.

Corneal thickening occurs because of swelling or fluid build-up in the cornea.

This can occur after the eyes have been closed or have had pressure applied to them for a period of time. Once the eyes have been opened, the air dehydrates the cornea reducing its thickness and therefore restoring normal vision.

So, when performing a treatment on around the eye for any length of time always give the client time to readjust and regain their vision as this could take a minute or two.

 

EYELIDS

The eyelids perform the function of protecting the eyeballs (the eyelashes are part of this process) they protect the eyeball from foreign objects, perspiration, and dust.  When the tear ducts produce tears, the eyelid enables this moisture to be spread over the eye and provides moisture and protection.

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