Dr. Tavel

Eyecare

How the Eye Works

 

Simply put, the human eye works similar to a camera. The eye focuses light onto the retina like a camera uses film. This basic diagram of the human eye shows how the different parts work together to see everything we take for granted.

The cornea is a transparent structure found in the very front of the eye that helps to focus incoming light. Just behind the cornea is a colored circular-shaped membrane called the iris. The iris has an adjustable opening called the pupil, which can expand or contract to control the amount of light coming through the eye. Your iris will enlarge in dim light, and contract in bright light to adjust for proper light to see. Light enters your eye through the lens and travels through the inside of your eye which is filled with a tissue called the vitreous humor and eventually hits a layer of cells called the retina. The retina is the innermost of three tissue layers that make up the eye and consists of millions of sensitive cells called rods and cones. When light hits the rods and cones, it's changed into a signal that is sent to the brain through the optic nerve. The brain then converts these signals into the images that we see.

Explanation of Common Eye Diseases

Cataracts

With age, the lens in the eye becomes hazy and cloudy.  The lens focuses images on the light sensitive nerve endings (the retina) in the back of the eye.  When it becomes cloudy, sharp images cannot be accurately focused.  The symptoms of cataracts often go unnoticed because the change is gradual.

Glaucoma

Glaucoma is the leading cause of blindness in the United States.  This condition typically involves an increase in intra-ocular pressure, but can occur with low or normal pressure as well.  It is typified by certain changes to the optic disk (the place where the optic nerve enters the eye) and by losses in the visual field - a narrowing of peripheral vision.

Presbyopia

As you enter your forties, you may find that you need to hold reading matter farther out in order to comfortably focus on it. This is because the lens of the eye becomes less flexible as we age.  The lens focuses images on the light sensitive nerve endings (the retina) in the back of the eye by adjusting it's shape according to its distance from the image being viewed.  As the lens becomes less flexible, it can no longer adjust itself to focus on near objects.