Technical Prescription DetailsUpdated 2 years ago
How do I read my prescription? What do all the abbreviations and numbers mean?
The key to reading your eyeglasses prescription, whether you have nearsightedness, farsightedness, astigmatism, or anything else, is knowing what OD and OS stand for.
Sometimes appearing as O.D. and O.S. (oculus dexter and oculus sinister), which are abbreviations in Latin for right eye (OD) and left eye (OS). Some doctors may use O.U. which means both eyes, or RE and LE for right eye and left eye, respectively.
There are other abbreviations in your eye prescription.Here is what each of them means:
Sphere (SPH): Measured in diopters, the number under this header refers to the lens power necessary for each eye. A minus (-) is used to correct nearsightedness. A plus (+) sign next to the number refers to farsightedness correction.
Cylinder (CYL): The lens power (also diopters) used to correct astigmatism. If you have no astigmatism or very slight one, nothing will appear under this column. Just like with Sphere, minus is used to indicate lens power for nearsighted astigmatism, plus is for farsighted astigmatism.
Axis (Ax): Like Cylinder, this only applies to astigmatism prescriptions. The numbers under this column refer to angle degrees (1 to 180) and not diopters. If your prescription includes Cylinder lens power, it must include Axis as well.
Add: Only used for multifocal (progressive/bifocal) lenses. It refers to the added magnifying power applied to the bottom of the lens in multifocal lenses. PAL is used in some cases by eye doctors when the addition for progressive lenses is different compared to bifocals.
Prism: Prism is used to correct double vision or vision displacement. The value on the prescription refers to the number of diopters applied to compensate for the image alignment issues.
Segment Height: SH or seg is the vertical measurement in millimeters from bottom of the lens to the beginning of the progressive addition on a progressive lens, or the top line of a lined bifocal. Segment height does not apply to single vision.
Sometimes appearing as O.D. and O.S. (oculus dexter and oculus sinister), which are abbreviations in Latin for right eye (OD) and left eye (OS). Some doctors may use O.U. which means both eyes, or RE and LE for right eye and left eye, respectively.
There are other abbreviations in your eye prescription.Here is what each of them means:
Sphere (SPH): Measured in diopters, the number under this header refers to the lens power necessary for each eye. A minus (-) is used to correct nearsightedness. A plus (+) sign next to the number refers to farsightedness correction.
Cylinder (CYL): The lens power (also diopters) used to correct astigmatism. If you have no astigmatism or very slight one, nothing will appear under this column. Just like with Sphere, minus is used to indicate lens power for nearsighted astigmatism, plus is for farsighted astigmatism.
Axis (Ax): Like Cylinder, this only applies to astigmatism prescriptions. The numbers under this column refer to angle degrees (1 to 180) and not diopters. If your prescription includes Cylinder lens power, it must include Axis as well.
Add: Only used for multifocal (progressive/bifocal) lenses. It refers to the added magnifying power applied to the bottom of the lens in multifocal lenses. PAL is used in some cases by eye doctors when the addition for progressive lenses is different compared to bifocals.
Prism: Prism is used to correct double vision or vision displacement. The value on the prescription refers to the number of diopters applied to compensate for the image alignment issues.
Segment Height: SH or seg is the vertical measurement in millimeters from bottom of the lens to the beginning of the progressive addition on a progressive lens, or the top line of a lined bifocal. Segment height does not apply to single vision.
What is pupillary distance (PD)?
The distance between your pupils. This measurement is used for an accurate determination where you look through the lens of glasses or sunglasses.
How can I measure pupillary distance (PD)?
Learn how to measure your PD if it is not included in your prescription.
Measure PD with a Ruler and a mirror
1. Stand 8 in away from a mirror.
2. Hold a ruler against your brow line.
3. Close your right eye
4. Align the ruler’s 0 mm with the center of your left pupil.
5. Look straight ahead.
6. Close your left eye and open your right eye.
7. The mm line that lines up to the center of your right pupil is your PD.
8. You now have a single PD measurement.
Measure PD with a Ruler and a mirror
1. Stand 8 in away from a mirror.
2. Hold a ruler against your brow line.
3. Close your right eye
4. Align the ruler’s 0 mm with the center of your left pupil.
5. Look straight ahead.
6. Close your left eye and open your right eye.
7. The mm line that lines up to the center of your right pupil is your PD.
8. You now have a single PD measurement.
What is the difference between standard and high-index lenses?
Our standard lenses are made with polycarbonate, an extremely tough transparent plastic with impact resistance. High index lenses are thinner, more powerful lenses. They're lightweight and stylish, but are mostly reserved for those with higher vision correction needs. While most prescriptions are compatible with more than one specific index, it's up to you to decide which one fits your personal needs
Do you offer prescriptions with prism correction?
Currently we do not have prism correction service available.
Are there any limits on the types of prescriptions you can fill?
We currently offer prescription lenses in single vision and progressive. Most of our prescription frame assortment will support total power ranges from -9 to +3. To calculate your total power range, simply add the sphere and cylinder numbers together. You will have to repeat this for both eyes to ensure both prescriptions can be fulfilled. For example, if your sphere is -2.75 and your cylinder is -.75 for your left eye, your total left eye power is -3.5. -2.75 + -.75 = -3.5. LEFT (OS) Left Sphere: -8 to 3 (OS) Left Cylinder: -3 to 3 (OS) Left PD: 27 to 37 (OS) Left Axis: 0 to 180 RIGHT (OD) Right Sphere: -8 to 3 (OD) Right Cylinder: -3 to 3 (OD) Right PD: 27 to 37 (OD) Right Axis: 0 to 180