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All about the EYE

To understand how the human eye works, first imagine a photographic camera – since cameras were developed very much with the human eye in mind.

How do we see what we see?

Light reflects off of objects and enters the eyeball through a transparent layer of tissue at the front of the eye called the Cornea. 

The Cornea accepts widely divergent light rays and bends them through the pupil – the dark opening in the center of the colored portion of the eye.

The pupil appears to expand or contract automatically based on the intensity of the light entering the eye.  In truth, this action is controlled by the iris – a ring of muscles within the colored portion of the eye that adjusts the pupil opening based on the intensity of light.  (So when a pupil appears to expand or contract, it is actually the iris doing its job).

The adjusted light passes through the lens of the eye.  Located behind the pupil, the lens automatically adjusts the path of the light and brings it into sharp focus onto the receiving area at the back of the eye – the retina.

An amazing membrane full of photoreceptors (a.k.a. the “rods and cones”), the retina converts the light rays into electrical impulses.  These then travel through the optic nerve at the back of the eye to the brain, where an image is finally perceived.

Main parts of the human eye include:

Cornea – transparent tissue covering the front of they eye that lets light travel through

Iris – a ring of muscles in the colored part of the eye that controls the size of the pupil

Pupil – an opening in the center of the iris that changes size to control how much light is entering the eye

Sclera – the white part of the eye that is composed of fibrous tissue that protects the inner workings of the eye

Lens – located directly behind the pupil, it focuses light rays onto the retina

Retina – membrane at the back of the eye that changes light into nerve signals

Rods and cones – special cells used by the retina to process light

Fovea – a tiny spot in the center of the retina that contains only cone cells.  It allows us to see things sharply

Optic Nerve – a bundle of nerve fibers that carries messages from the eyes to the brain

Macula – a small and highly sensitive part of the retina responsible for central vision, which allows a person to see shapes, colors, and details clearly and sharply.

Eight Ways to Protect Your Eyesight

Be aware of your risk for eye diseases – Find out about your family’s health history

Have regular exams to check for diabetes and high blood pressure – If left untreated, these diseases can cause eye problems

Look for changes in your vision – If you start noticing changes in your vision, see your eye doctor immeciately

Exercise more frequently – Some studies suggest that regular exercise such as walking, can reduce the risk of macular degeneration by up to 70%

Protect your eyes from the sun’s UV rays – You should always wear sunglasses with proper UV protection to shield your eyes from the sun;’s harmful rays.

Eat a healthy and balanced diet – Numerous studies have shown that antioxidants can possibly reduce the risk of cataracts.

Get your eyes checked at least every two years – A thorough eye exam, including dilating your pupils, can detect major eye diseases such as diabetic retinopathy, which has no early warning signs or symptoms.

Don’t smoke – The many dangers of smoking have been well documented.  When it comes to eye health, people who smoke are at greater risk of developing age-related macular degeneration and cataracts.

Source:  AllAboutVision.com 2009 Access Media Group LLC.  All rights reserved.

Information provided by EyeGlass Guide