If you’d had your eye checkup recently, do you remember it turning out this way: you are asked to peer through a machine and focus on a photo of a balloon or a house in a field; afterwards, you will be taken to a room and asked to wear frames with removable lenses while being instructed to read out the letters of Snellen scale through a mirror. After all of these, you will be handed your printed grade reading that you can’t seem to make a lot of sense of. So what do the digits in that small sheet mean?
OD/R & OS/L
OD means oculus dexter and OS means oculus sinister; they are Latin terms that mean “vision in the dexter eye” and “vision in the sinister eye”. Simply, OD and OS are the readin for your right and left eyes respectively. Sometimes, it’s easier to understand because they will just use R/L.
Next to or below OS & OD, you will find a value with a + or – sign before it. This value indicated near- or farsightedness. Near sightedness is indicated with a – sign while farsightedness is indicated with a + sign. The values are diopters in increments of .25 you if your prescription has the value of -0.25 or +3.75. up you have nearsightedness at .25 diopters or farsightedness at 3.75 diopters; the greater the value, the stronger the prescription.
SPH or just S means Sphere; this means that although there is a nearsighted or farsighted correction needed, the lens power is spherical or equal in shape to the eye unlike with astigmatism. You will commonly hear these terms mentions during your eye checkup.
If Sphere indicates the lens power for myopia or near-/farsightedness, CYL or cylinder indicates the lens power for astigmatism. Instead of being spherical, the eye is shaped more like a football. If you have astigmatism, your prescription might have 2 values, on for SPH correct and another for CYL. Sometimes, it might also include AXIS.
Axis indicates the orientation of the astigmatism. Imagine your eye as a football; their pointy ends could be pointing up and down, or side to side. The angle by which they point is what is indicated by the Axis. If your prescription has Axis, you might see values indicated as SPH x CYL x Axis.
It might look something like this:
-.25 -.75 x 45
Aside from being fitted to the correct prescription, you might want to add a coating to your lenses as well. You will find these specifications under this area. You might see hand written here words like “multicoated” or “anti-radiation” or “blue light”.
Next time you get an eye checkup, you can be more confident knowing that you understand how your prescription works! See and understand how much your eye sight has improved or by how much did your prescription get stronger.