Thinkzo: Resource Article

A Guide to Eyes

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I've assembled here a brief and simple guide to some of the jargon one might hear associated with the eyes or eyesight. I hope you find it useful. This is, by no means, a complete list. Also, you should not use this guide as a replacement for an eye doctor or eye specialist. It's intended only to inform and educate on the simplest terms.

Cornea
Thin, clear covering over the surface of the eye. A cornea transplant is sometimes inaccurately referred to as an eye transplant. The cornea assists the lens with focusing light on the retina. Infection or injury to certain areas of the cornea can cause total or partial vision loss. Some persons are blind or seriously visually impaired due to such corneal damage, while their eye is otherwise fully functional, so an operation to correct this corneal damage could lead to restored vision.

Schelera
The white portion of the eye.

Iris
The colored portion of the eye surrounding the pupil. It's the iris people are referring to when they talk about eye color. It functions similarly to the mechanical iris of a camera, allowing more or less light to enter the eye chamber.

Pupil
The center black portion of the eye inside the iris. It's a fluid filled hole which allows light to enter the eye chamber.

Lens
Situated within the front center of the eye, helps to focus light entering the eye chamber onto the retina at the back of the eye chamber. It works in conjunction with the cornea to focus the light on the retina. The overall health of the lens and its ability to allow and focus light on the retina is most often affected by a normal part of the aging process in the form of cataracts. Once the cloudy lens is replaced, normal vision is usually restored.

Retina
Thin layer of light sensitive cells lining a region along the back of the eye chamber. The light sensitive cells react to light focused on the retina by the lens and cornea and transmit that information along the optic nerve to the brain for processing. Any kind of damage to the retina can cause partial or total vision loss. There are varying degrees of success in restoring vision through retinal repair or replacement, but such surgery is still very much in its infancy compared to cataract or glaucoma surgeries.

Optic Nerve
Transmits information or signals from the eye to the part of the brain that deals with vision. A person can have an otherwise functional eye and have little or no vision because the optic nerve has been damaged by glaucoma or some other injury. There's currently no surgical replacement for the optic nerve, which is why it's so important to catch glaucoma problems as soon as possible before they do their damage.

GLAUComa
A noncurable condition whereby the fluid that regularly circulates through the eye chamber is either in too short or too great a supply. The latter is probably more common, creating increased eye pressure that can eventually cause total or partial vision loss. The increased pressure interferes with the blood supply to the optic nerve and the nerve begins to die out as a result. The increased pressure can often be controlled, but not cured, through eyedrops in it's early stage and with laser or other surgical methods in later stages. There's generally no pain associated with glaucoma, which is why it's so important for people to get their eye pressure checked on a regular basis, particularly as they get older.

Cataract
A clouding of the lens of the eye that prevents light from entering or properly focusing on the retina. Has several known causes, but is most often due to aging. There are various surgical procedures that can be used to replace the clouded lens with a new, clear lens, restoring proper vision. Many people can often see better after cataract surgery than at any other time in their lives, often being freed from glasses or contact lenses - this is done by introducing some prescriptive correction in the replacement lens. There is no pain associated with cataracts, other than that possible from having some accident due to not being able to see well enough to avoid the accident.

Retina Detachment
Occurs when the retina tears or detaches. The result is loss of vision in that area of the eye, since the cells in the retina cannot transmit their information along the optic nerve to the brain any longer. There's no pain associated with the retina detachment itself. It's possible to repair a partially detached retina in most cases, and currently possible to repair a totally detached retina in some cases, if medical attention is sought quickly enough. Vision can be nearly as good as before under most conditions. Retina detachments can occur for a variety of reasons, from eye trauma to eye disease.

Eye Transplant
Based on current medical knowledge and technology, it's not possible to transplant an entire eye to allow persons to see again. What's most often refered to as an eye transplant, is instead a cornea transplant.

Eye Pressure
A measure of the pressure within the eye chamber. Different eye doctors or specialists have differing opinions of what is considered "normal" eye pressure. It's the fluid that regularly circulates through the eye chamber that defines eye pressure. One of the functions of eye pressure is to maintain the orb, or proper shape, of the eye chamber. Eye pressure isn't related to blood pressure. There's generally no pain associated with either low or high eye pressure, which is why glaucoma is so dangerous as there's no warning of any problem. There's generally no pain associated with having one's eye pressure checked - the only relatively mild side effect may be a tired feeling in the eyes caused by the numbing drops applied prior to the pressure being checked.

Dilate, or Dilation
Eyedrops are applied in the eye during an eye exam which cause the pupil to dilate or expand. This allows the eye doctor or eye specialist to get a good view inside the eye chamber. There's generally no pain associated with having your eyes dilated. The main side effects are sensitivity to light, and blurred vision which tend to disappear after a few hours - wearing a good pair of sunglasses after having your eyes dilated will make things more comfortable.

On the Horizon...

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