When you visit an optometrist for an eye exam, you may receive a prescription for glasses or contact lenses. However, many people find it difficult to understand the terms and numbers on their prescription. Understanding these results is crucial to ensuring you get the right corrective lenses to improve your vision. We at Delray Optical would like to offer a guide to help you decode the components of your eye exam prescription and what they mean for your eye health.
Sphere (SPH)
The sphere (SPH) value on your prescription indicates the strength of your lens prescription. This number represents the degree of nearsightedness (myopia) or farsightedness (hyperopia) you have. If the number is negative, it indicates that you are nearsighted, meaning you have difficulty seeing objects at a distance. On the other hand, a positive number indicates farsightedness, where you struggle to see objects up close.
For example:
-2.00 SPH means mild nearsightedness.
+2.00 SPH means mild farsightedness.
The higher the absolute number, the stronger the prescription needed.
Cylinder (CYL) and Axis
If you have astigmatism, which is a common condition caused by an irregularly shaped cornea, your prescription will also include a Cylinder (CYL) value and an Axis measurement.
Cylinder (CYL): This indicates the amount of astigmatism you have and how much correction is needed to address it. Like the SPH number, the CYL value can be positive or negative. A negative value indicates that the astigmatism is correcting nearsightedness, while a positive value corrects farsightedness.
Axis: The axis number represents the orientation of the astigmatism in degrees. It ranges from 1 to 180 and shows where the cylinder correction should be applied to best correct your vision.
For example:
-1.50 CYL and 180 Axis means the prescription is for correcting nearsighted astigmatism in a horizontal orientation.
Prism
Some prescriptions will also include a Prism value, which is used to correct binocular vision problems, like when your eyes don’t align properly. The prism helps to reduce double vision or other issues caused by eye misalignment. If your prescription has a prism value, it will be accompanied by a direction in which the prism is to be applied (e.g., base up, base down, base left, or base right).
Add
If you’re over the age of 40 and need reading glasses or multifocal lenses, you might have an Add value on your prescription. This value indicates the additional magnifying power required for close-up work like reading or sewing. The Add value is always a positive number and is usually the same for both eyes.
For example, if your prescription shows +2.00 Add, it means you need +2.00 diopters more power for close-up vision.
OD and OS
On your prescription, you will see abbreviations for each eye:
• OD: Oculus Dexter (right eye)
• OS: Oculus Sinister (left eye)
Each eye will have its own set of values based on its specific visual needs. If both eyes require the same prescription, the numbers will be identical; otherwise, there will be slight variations between the two.
Understanding the Prescription Format
An eye prescription typically looks like this:
• OD: -2.00 SPH, -0.50 CYL, 180 Axis
• OS: -1.50 SPH, -0.75 CYL, 170 Axis
This means that the right eye has mild nearsightedness and a small amount of astigmatism, with a correction axis at 180 degrees. The left eye has slightly less nearsightedness, more astigmatism, and a correction axis at 170 degrees.
Eye Exams & More in Delray Beach, FL (Just Minutes Away from Boca Raton, Highland Beach, Kings Point, Golf & Boynton Beach, Florida)
Understanding your eye prescription can seem complicated at first, but knowing what the different numbers mean can help you choose the right lenses to correct your vision. If you have questions or are unsure about your prescription, don’t hesitate to ask your optometrist for clarification. Proper eyewear can significantly improve your vision, making daily activities easier and more enjoyable. Call Delray Optical to schedule your eye exam.
