Different types of prescription eyeglassesWritten by Timothy Gorman
Prescription eyeglasses are glasses that have been prescribed by an optometrist to be worn by someone who has been diagnosed with a certain eye condition. Depending on condition, a different lens will be prescribed.Prescription eyeglasses are broken down into four different categories. The Single Vision Lens has same focal power from top of lens to bottom of lens. People who have been diagnosed as farsighted, nearsighted or with having astigmatism can wear single vision lenses to correct these types of eye disorders. Astigmatism is a condition that doesn't allow light to reflect on retina, thus causing distorted images. A Bifocal Lens is used to correct a condition call Presbyopia. This disorder usually occurs in people in their late 40's. If a person has been diagnosed with Presbyopia, they can't focus in on close objects. That is where Bifocal Lens is helpful. The top of lens is used for distant vision and bottom of lens is helpful with close vision. People with Presbyopia need both types of Focal View on their prescription eyeglasses.
| | How long have prescription eyeglasses been around?Written by Timothy Gorman
From documents that were retrieved in Rome in 13th Century, we know that prescription eyeglasses were available at that time. They were referred to as "spectacles" rather than glasses. Although we do not know for certain when prescription eyeglasses were invented, we do have proof that they did exist during this time period. A portrait done by an artist named Tomas da Modeno portrays a gentleman wearing eyeglasses. Obviously what we do not know is if they are prescription eyeglasses. There are, however, other documents such as a manuscript written by a man that implies that if he wasn't wearing spectacles, he would not be able to read or write.In 15th century printing press was invented which meant more reading material was readily available. Thus, need for prescription glasses increased. The first reading glasses were held by one hand only during times that they were needed for reading. It was later in 17th century when people actually wore glasses regularly, after an optometrist created them with both earpieces. In those times, a person who was having difficulty with their eyesight would just go in and try on several pairs of prescription eyeglasses until they found a fit for their needs. That changed when Dr. FC Donders wrote first book on examining eyes to get prescription eyeglasses.
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