Understanding Your Eyeglass Prescription

If you need eyeglasses it is because you were diagnosed with a refractive error during your eye exam. This means your eyes have trouble focusing and images can appear blurry. Types of refractive errors include being near-sighted (myopia), far-sighted (presbyopia) or having an astigmatism (your cornea is an irregular shape).
Understanding Your Eyeglass Prescription

Understanding What 20/20 Vision Means

The number is based on you standing a distance of 20 feet (considered to be the norm) in front of a Snellen or Tumbling E eye chart to test your visual acuity. If during an eye test you can read the big E at the top of the eye chart, but none of the letters below that, your vision is considered 20/200. That means you can read a letter at 20 feet that people with “normal” vision can read at 200 feet, meaning you have very poor visual acuity. If you can read the fourth line from the bottom of most charts, you vision is 20/20. Any line below that would be 20/15 or below and indicates that you have exceptional visual acuity. Each eye is tested separately as your eyes are designed to compensate for each other and would not give an accurate reading.

Understanding Your Eyeglass Prescription

The prescription you receive may be a chart with headings that are filled in, or it may just be written out. In any case, it is written in a specific order, with the results for each eye listed first.

  • OD is an abbreviation for oculus dexter, meaning right eye, while OS is oculus sinister, meaning left eye. If both eyes are being referred to the abbreviation you will see is OU (oculus uterque) meaning both eyes.
  • The next term on your prescription is Sphere (SPH) and is are measured in diopters (D). This number tells you how strong your lenses need to be to correct your vision. If this number has a minus sign (–), you are nearsighted; if the number has a plus sign (+) or is not preceded by any sign, you are farsighted.
  • Next may be cylinder (CYL), an indicator of the lens power if you have an astigmatism. The number for the CYL has the same format as the SPH, a minus sign (for the correction of nearsighted astigmatism) or a plus sign (for the correction of farsighted astigmatism). If there is no number given you either have no astigmatism, or your astigmatism is so slight that it is not really necessary to correct it.
  • If you do have a CYL number you will also have an axis number, based on a protractor scale that tells you where on the eye the astigmatism is found. For example, SPH –2.50 D CYL +5.00 Axis 40 means you have a nearsightedness of -2.50 dioptics with an astigmatism of +5.00 along the 40 degree axis.
  • If you are getting bifocals or progressive lenses, there is another number called an “Add.” This number is the amount of additional correction your eyes need to focus at close distance and will always be a positive number, whether or not the + sign is there.

Needless to say, eyeglasses are expensive, but understanding a prescription should help you understand why. The stronger the lens the more expensive it is and then with each adjustment, the cost also increases. Also don’t forget that anti-glare or UV protective coatings add to the costs, but may be well worth it. Eye glasses are an investment in your safety, job, independence and letting you enjoy any leisure-time activities you enjoy.

2/9/16

 

Susan DeRemerSusan DeRemer, CFRE
Discovery Eye Foundation

Purpose of Eye Exams for Children

Many children who are 6 – 18 years old are now back in school or will be shortly. But have you given them everything they need to succeed in the school year ahead?

      ? New binders
      ? Notebook paper and dividers
      ? Pencil box filled with pens and pencils
      ? Calculators, protractors and rulers
      ? Backpack to carry it all

These are the tools that children and their parents focus on every year, thinking these will help their child have a fun and productive year. But the list is incomplete. For school-aged children, the AOA recommends eye exams for children every two years if no vision correction is required. Children who need eyeglasses or contact lenses should be examined annually or according to their eye doctor’s recommendations.

“But my child gets and eye screening at school every year…” While this may be true it is important to understand the difference between a screening and an eye exam.

Vision screenings are a short examination that can indicate a vision problem or a potential vision problem; however it cannot diagnose exactly what is wrong with your eyes. It can also easily miss vision issues, giving parents a false sense of security.

With an eye exam, the tests are performed by a trained professional, using specialized equipment looking for specific indicators that could affect your child’s vision. They test much more than how well your child can read letters or symbols at a distance.

Good vision is necessary for a child to succeed at school and not become frustrated or depressed. It has been estimated that as much as 80% of the learning a child does occurs through his or her eyes. Children need to read a book and see a whiteboard, write and use computers every day in the classroom and at home. When a child cannot see clearly, it becomes more difficult to learn.

It also goes beyond just seeing clearly. Your child needs their eyesight to understand and respond to what they see. This includes the ability to focus their eyes, use both eyes together, and move them effectively.

Infographic - eye exams for children

Children may not always know they have a vision problem because they think that everyone is seeing the way they do. There are some signs that may indicate a vision issue:

  • Repeated eye rubbing
  • Excessive blinking
  • Short attention span
  • Tilting the head to one side or covering one eye
  • Holding reading materials too close to the face
  • Losing their place when reading
  • Difficulty remembering what they just read
  • Trying to avoid reading or other close activities
  • Numerous headaches

So as you prepare your child to go back to school, give them the best advantage they can have – good vision. Make an appointment with your eye doctor today.

8/27/15


Susan DeRemerSusan DeRemer, CFRE
Vice President of Development
Discovery Eye Foundation