I got a copy of my spectacle prescription and it’s a lot of numbers. What do they represent?
The prescription for the right eye may have just one number, like +2.00 or -1.00. A prescription like this means you are either farsighted or nearsighted and represents the spherical correction required for the eye.
People with nearsightedness (myopia) see objects up close clearly, but far images are blurred. A sign of nearsightedness is difficulty seeing distant objects like a TV screen or blackboard. This occurs either if your eyeball is a little elongated, or the cornea (the front surface that refracts the light) had too much curvature. When this happens, the image you see is not focused on the retina, but in front of it. You then need a concave shaped lens to change the direction of the light. These lenses are minus (-) powered lenses.
People who are farsighted (hyperopic), see distant objects clearly, but close-up images are blurry. Common signs of farsightedness include difficulty in concentrating and keeping a clear focus on near objects, eye strain, fatigue, and headaches after close work/reading. Farsightedness occurs if your eyeball is too short or the cornea has too little curvature, so light entering your eye is not focused correctly. When this happens, the image you see is not focused on the retina, but in front of it. You then need a convex-shaped lens to change the direction of the light. These lenses are plus (+) powered lenses.
If your prescription has 3 numbers, like -1.00 -1.50 x 180, it means that you have astigmatism. Common signs of astigmatism include blurry vision at distance and near, eye pain while reading, and occasional headaches. Astigmatism occurs when the cornea is irregularly shaped, more egg-shaped than round. In this prescription, the cornea needs -1.00 power along one direction and an additional -1.50 power along the other direction. You then need a lens that corrects along these 2 meridians (directions). This type of lens correction is called a cylindrical lens.
If you are over 40 years old, you lose the ability to see things up close and need bifocals. It means that you need more power to see near, and you require additional power over the distance prescription. The prescription will then read either +200 add +1.50 for a spherical correction, or -1.00 -1.50 x 180 add +1.50 for a person who has astigmatism as well as a bifocal addition.
