lens measurements
What Do SPH, CYL, AXIS and ADD Mean on a Glasses Prescription?
Learn what the common eyeglass prescription fields mean, how to read each eye's row, and what to check before ordering replacement lenses.
Lenshaus Editorial Team ·
SPH, CYL, AXIS and ADD describe different parts of an eyeglass prescription. SPH is the main lens power. CYL and AXIS describe astigmatism correction when prescribed. ADD is extra power for near vision. Read the right and left eye rows separately, and copy every sign, decimal and number exactly as written.
Start with the right eye and left eye
Most prescriptions have a row for each eye. The right eye may be labeled OD, and the left eye may be labeled OS. Do not assume the two rows match. If a value is hard to read, ask your prescriber to confirm it. The Lenshaus team can also help you review what to enter before continuing.
SPH: the main lens power
SPH stands for sphere. It describes the lens power used to correct nearsightedness or farsightedness. A minus sign usually indicates nearsightedness, while a plus sign usually indicates farsightedness. The number is measured in diopters. Keep the plus or minus sign when copying it.
CYL and AXIS: astigmatism correction
CYL stands for cylinder. If your prescription includes astigmatism correction, CYL gives the amount and AXIS gives its orientation in degrees. AXIS is an angle, not another lens power. Keep each eye's CYL and AXIS together. A prescription may leave both fields blank when no astigmatism correction is prescribed.
ADD: extra near-vision power
ADD is additional power for near tasks. It can appear on prescriptions for bifocal or progressive lenses. If your prescription has an ADD value, ask your prescriber or the Lenshaus team for guidance about which lens design fits your needs rather than choosing from the abbreviation alone. If you are considering multifocal lenses for frames you already own, read our guide to progressive lenses in existing frames.
What about PD or other fields?
Pupillary distance, or PD, is a fitting measurement that may be recorded separately from your prescription. Our missing PD guide explains where to look and what to do if you cannot find it. If your prescription also lists prism or base, keep those details with the full prescription and ask for help if you are unsure how to enter them.
Ready to choose replacement lenses?
In the Lenshaus lens builder, you can upload a prescription image or enter its values manually. Before continuing, check the eye labels, signs and any CYL, AXIS or ADD entries against the original document. For help understanding your prescription or choosing a lens option, schedule a call with the Lenshaus team.