Ever look at your glasses prescription and wonder what it all meant,  We are going to have your glasses prescription decoded and explain what it all means. When you look at the prescription, you will see two sets of numbers under the headings of OD and OS. They are abbreviations from the Latin forms of right and left eye.


OD (Oculus Dextrus) means right eye
OS (Oculus Sinister) means left eye

For those patients who have no astigmatism (spherical eyes) and do not require a multifocal or prism, there will be one number for each eye. This number is known as the sphere portion of the prescription. The farther away from zero this number is, the worse your eyesight is. A plus sign in front of this number indicates you are farsighted (need glasses to see up close) and a minus sign in front of the number indicates you are nearsighted (need glasses to see far away). The number shows how many diopters a patient needs to correct their sight.

For example, if your glasses prescription read:

OD: -3.00
OS: -4.25

That would mean that your right eye has 3D of nearsightedness and your left eye has 4.25D, and that your left eye requires more correction than your right.

For people who have astigmatism (non-spherical eyes), there will be at least three numbers for each eye in your prescription. The first number is the sphere which is the amount of nearsightedness or farsightedness. The second number is the cylinder. This represents how much astigmatism measured in diopters is in the eye. The larger the number, the more astigmatism there is. The last number is the axis which is between 0 and 180 degrees and allows the lad to orient the astigmatism correction in your glasses or contacts.

For example, if your glasses prescription read:

OD: -3.00 -0.50 x 090
OS: -3.50 -1.00 x 105

That would mean that your right eye has 3.00 diopters of nearsightedness with 1/2 diopter of astigmatism at an axis of 90 degrees. Your left eye has 3.50 diopters of nearsightedness with 1.00 diopter of astigmatism at 105 degrees. The left eye in this example has both more nearsightedness and more astigmatism.