DR. BOB'S BLOG
posted: Apr. 24, 2018.
You just had your eye examined and your Optometrist hands you a piece of paper with your prescription on it.
Here is what all those numbers mean.
O.D. stands for oculus dexter - latin for right eye
O.S. stands for oculus sinister - latin for left eye
The first number is the called the SPHERE. A plus sphere means is for farsightedness - you have difficulty focusing on close objects. This is called hyperopia. The number can range from +0.25 to +6.00. A minus sphere is for nearsightedness - you have difficulty focusing on distant objects. This is called myopia. The numbers can range from -0.25 up to -10.00.
The second number in the prescription is the CYLINDER. This number is the astigmatism correction. The cornea is irregularly shaped so the light is not focused evenly. The cornea is not round like a baseball it is more irregular like a football. It can cause blurry, fuzzy or distorted vision.
The third number is called the AXIS. It is measured in degrees. It is where the astigmatism is on your eye.
Then you may have a ADD number on your prescription. This is for the the reading correction. This measurement can be used to make a bifocal lens, trifocal lens or progressive lens. This is called presbyopia - when your eyes gradually lose the ability to see things clearly up close. It is a normal part of aging. You might start to notice presbyopia shortly after turning 40. You will find you need to hold reading materials farther away to see clearly.