There are estimated 168 million people who wear prescription eyeglasses in the United States. Only a very small percentage of those people could tell you what strength their lenses are or read an eyeglass prescription.

The strength of prescription eyeglasses is measured in what we call diopters. Optometrists abbreviate that with a D. The stronger the lens, the higher the diopter measures. Prescription eyeglass lenses are measured in positives or negatives. If you look through a negative lens the object that you are focusing on will look smaller. If looking through a positive lens, the object will look bigger.

There are three professions that deal with prescription eyeglasses that many people are not aware of. The first profession is called an Optician. An Optician makes the lenses, frames and contact lenses. They analyze the prescription and then dispense medications and prescription eyeglasses.

The Ophthalmologist is an eye doctor who is licensed to perform surgeries that are needed to correct vision or aid in curing eye diseases.

The Optometrist is the eye doctor who usually will give the eye exam and checks for any diseases and medical conditions. They are licensed to dispense prescription eyeglasses and medications.

There are three very common eye disorders that can be treated by wearing prescription eyeglasses.

* Mypoia, another name for nearsightedness. The symptoms are blurred vision and inability to focus on objects that are in the distance.

* Hyberopia, which means farsightedness. It is the opposite of Myopia. The symptoms are headaches, eye fatigue after reading or watching television.

* Glaucoma, which is the build up of fluid on the retina. There are no warning signs to this disease and it can cause loss of sight if left untreated.

A person should have their eyes examined by an optometrist every two years until they are the age of 60 then the examinations should be annually.