How do I read my glasses prescription (SPH, CYL, AXIS, ADD)?
By Abhay Kumar, founder of ORINvue · 2026-10-19 Your prescription lists numbers for the right eye (OD) and left eye (OS). SPH tells the main power (minus for short-sightedness, plus for long-sightedness), CYL and AXIS describe astigmatism, and ADD is the extra power for reading. A bigger number means a stronger power. Once you know these five terms, you can read any prescription slip in minutes. OD and OS OD means right eye and OS means left eye (from the Latin terms). Some slips write R and L, and OU means both eyes. The two eyes often have different numbers, which is normal. SPH: sphere This is the basic focusing power, measured in dioptres. A minus sign (for example -2.50) means short-sightedness (myopia): distant things look blurry A plus sign (for example +1.75) means long-sightedness (hyperopia): near work is tiring and distance may blur as well Plano or 0.00 means no spherical power needed CYL: cylinder This shows astigmatism, where the front of the eye is shaped more like a rug...