Unless you have a Doctor of Optometry degree, your eyeglass prescription probably does not make sense, especially if you are getting glasses for the first time. Throw in all the different types of glasses — single vision, lined bifocals, unlined bifocals, trifocals, reading glasses, etc. — and the confusion doubles. Going to your eye exam armed with knowledge about these types of prescriptions and an understanding of how to read a prescription can help you make a knowledgeable decision when it comes time to pick out your glasses.
How to Read an Eye Prescription
Trying to decipher an eyeglass prescription can be frustrating, but it is simply a matter of understanding for what the letters and numbers stand. Your prescription most likely has numbers underneath the abbreviations OS and OD. OS (oculus sinister) represents your left eye, and OD (oculus dextrus) your right eye. Some prescriptions simply refer to your eyes as “left” and “right.” If the numbers underneath OS and OD have a minus sign, that means you are nearsighted. A plus sign means you are farsighted and need reading glasses. The numbers themselves describe how much correction your eyes need; the numbers are measured by units called diopter. Usually, the worse your eyesight is, the further from zero the number will be.
If there are three numbers in your prescription, you probably have an astigmatism. The first number represents your nearsightedness or farsightedness. The second number describes how much correction your astigmatism needs, and the third number is a degree between 0 and 180. This third number is referred to as the axis, and it represents where the astigmatism is in your eye.
Resources on How to Read an Eye Prescription
- All About Vision: “How to Read Your Eyeglass Prescription”
- NetWellness Explanation of a Nearsighted Prescription
- Eyeglass Guide: “Prescription Glasses: More than Meets the Eye”
- WebMd: “How to Read Your Eyeglass Prescription”
- USAEyes: “How to Read Eyeglass or Contact Lens Prescription”
Single Vision Lenses
Single vision prescription lenses contain the same amount of vision correction over the entire lens. These lenses can correct nearsightedness, farsightedness, and astigmatism. Single vision lenses can come in a couple varieties. In terms of reading glasses, full frame reading glasses are your standard readers. Being wider, they provide a larger line of up-close vision. Single vision lenses can also be half frame reading glasses that are more narrow frames. These sit at the end of the nose, leaving your line of vision open for seeing things in the distance.
Resources on Single Vision Lenses
- VisionRX Definition of Single Vision Lens
- Heritage Vision Plans Definition of Single Vision Lens
- All About Vision Advantages of Single Lenses
Lined Bifocals
Lined Bifocals can correct both nearsightedness and farsightedness by containing two different prescriptions within the same lens. Usually, lined bifocals contain a focal length that corrects close vision of 12 to 18 inches away from the face, as well as a focal length that corrects distances of 10 feet and beyond. When you are looking at someone who is wearing lined bifocals, you can see the line between their nearsighted and farsighted prescription.
Resources on Lined Bifocals
- WebMd: “Happy 40th — Here are Your Bifocals!”
- All About Vision Bifocals Explained
- U.S. Safety: “Progressive Lens (No-Line Bifocal) vs. Line Bifocal
Progressive Lenses
Unlined bifocals, commonly known as progressive lenses, contain two different prescriptions within the same lens. Unlike lined bifocals, no line bifocal reading glasses have no visible line between the nearsighted and farsighted prescription. This lack of a visible line between the prescriptions not only makes the glasses more trendy, but it also gives the wearer a seamless and uninterrupted transition when looking from up-close objects to far-away distances.
Resources on Progressive Lenses
- Mayo Clinic Progressive Lenses to Treat Presbyopia
- All About Vision: “Q&A on Bifocal Eyeglasses, Progressive Lenses and Reading Glasses”
- All About Vision: “Progressive Lenses Replace Bifocals for Age-Defying Appearance”
- NetWellness: “Progressive Bifocals vs. Progressive Trifocals
- U.S. Safety Advantages and Disadvantages of Progressive Lenses
- Eyeglasses Guide: “What are Progressive Lenses?”
Trifocals
Trifocals contain three prescriptions within one lens. The top prescription corrects distance vision. The middle prescription corrects intermediate distances of 18 to 24 inches, which is good for computer use. The bottom prescription is for seeing up-close objects such as reading material. Some people do not like how trifocals look because the transitions among the prescriptions are visible; however, they are worth trying because of the additional vision field they provide.
Resources on Trifocals
- WebMd Trifocals and Presbyopia
- All About Vision: “Q&A on Bifocal Eyeglasses, Progressive Lenses and Reading Glasses”
- All About Vision: “Occupational Bifocals and Trifocals”
- All About Vision: “Bifocals and Trifocals: Solutions for ‘Short Arms’”
Nearsighted
A nearsighted individual has difficulty seeing far-away objects clearly. This occurs if the cornea is curved too much, or if the eyeball is too long. A child who is nearsighted will be able to read the words of a book well, but will have difficulty reading the words on a chalkboard. A prescription for someone who is nearsighted could be -1.25. Nearsighted prescriptions are signified with a minus sign, and they show how much correction you need to see far-away objects clearly. Nearsighted prescriptions increase at intervals of .25 diopter.
Resources on Nearsightedness
- American Optometric Association Information on Nearsightedness
- American Optometric Association: “Myopia FAQs”
- Mayo Clinic on Nearsightedness
- WebMd on Nearsightedness
- All About Vision on Nearsightedness
- American Optometric Association: “The Distance Prescription”
- American Optometric Association on Myopia
- WebMd: “How to Read Your Eyeglass Prescription”
- All About Vision: “How to Read Your Eyeglass Prescription”
Farsighted
People who are farsighted can see far-away objects with no problem, but close-up objects or reading material are blurry. This occurs when light that enters the eye focuses behind the retina instead of on it. A prescription for farsightedness always has a plus sign before the number. An example could be +1.25. Many people who are farsighted only wear their glasses when reading or doing something up close.
Reading glasses are good for people who spend a lot of time concentrating on close-up material. These will need to be taken on and off though, because if you try to see distance in your reading glasses things might appear blurry. Reading glasses come as full frame reading glasses where the entire lens contains the reading prescription. These are good for people who spend a significant amount of time reading up-close material. They also come in half frame reading glasses, or “half-eyes,” that sit low on the nose. These are good for people who look up and down often.
Resources on Farsightedness
- American Optometric Association: “Hyperopia FAQs”
- Mayo Clinic on Farsightedness
- WebMd on Farsightedness
- All About Vision on Farsightedness
- American Optometric Association Reading Prescription for Pilots
- American Optometric Association: “Adult Vision: 41 to 60 Years of Age”
- Mayo Clinic on Treating Presbyopia
- WebMd: “How to Read Your Eyeglass Prescription”
- WebMd on Presbyopia
- All About Vision: “How to Read Your Eyeglass Prescription”
- All About Vision: “Reading Glasses”
Computer Glasses
The lenses of computer glasses are specially developed to deal with the strain computer use has on the eyes. While most glasses either correct short or long distance problems, computer glasses are designed to help with an intermediate distance of around 20 to 26 inches, which is the distance most people sit from their monitor. The lenses also provide a wide and clear view of the screen. There are over-the-counter computer glasses, but it is best to get a prescription from the optometrist. It is helpful to measure how far you sit from your computer so the optometrist can give you the best prescription for your habits.
Resources on Computer Glasses
- American Optometric Association on Computer Vision Syndrome
- Mayo Clinic Computer Glasses as Solution for Eye strain
- All About Vision on Computer Vision Syndrome
- All About Vision: “Computer Glasses: Relieving Computer Eye Strain”
- The University of Michigan Kellogg Eye Center Computer Glasses Relieve Computer Eyes
- Indiana University News Room Computer Glasses Relieve Computer Vision Syndrome
