Do You Know Prescription Glasses?

Eyeglasses were invented almost eight centuries ago. This invention has allowed people to live their lives doing things most of us take for granted. Prescription glasses have enabled those with poor vision to live a better quality of life. Some of these opportunities we take for granted are driving a car, reading a book, watching television, and many others.

Human lenses are found between the retina and the cornea in the eye. This convex-shaped lens works with the cornea to focus on images and then project them onto the retina. The image is then sent from the retina to the brain for interpretation which allows us to see. Many different conditions can cause our eyes to focus incorrectly on images. The lens can lose it’s ability to curve and/or there may be a problem with the cornea. Whatever the reason these problems can result in our eyes being unable to focus on objects that are near or far away. The inability to focus on objects near to us is called farsightedness and the inability to focus on objects farther away is called nearsightedness.

Prescription glasses are made after the strength of the correction needed is determined. Normally this is done in a doctor’s office using an eye test. After the doctor has determined the prescription needed then the results are sent to a laboratory so the lenses can be created for the eyeglasses.

The laboratory starts with a blank lens made of either plastic or glass discs about four inches wide. The discs can be up to one and one-half inches thick. The lens has a flat back and a curved front surface. The technician takes the lens and grinds it to the required curve. The thickness of the lens is determined by the curve needed to fill the prescription along with the type of material the lens is made of.

The grinding of the lens for these prescription glasses takes a great deal of precision to ensure the eyeglasses are made exactly as prescribed. They also have to be made with no scratches that could affect the function of the lens. After the grinding process is complete they are fitted to the frame chosen by the patient. They are then tinted and coated for UV protection.

The frames are heated or treated with chemicals to make them flexible enough to insert the lenses. After insertion of the lens the prescription glasses are checked for any imperfections and to make sure the strength is correct. They are then cleaned and packaged and delivered to the doctor’s office where the patient can pick them up.