Decoding Your Glasses Prescription Guide | Generated by AI
Question: Explain this glasses prescription: SPH CYL Axis Right (OD) -4.50 -1.25 176 Left (OS) -2.25 -1.25 12 PD 70.5 mm
Answer:
This is a standard eyeglass prescription for correcting nearsightedness (myopia) combined with astigmatism in both eyes. The prescription is moderately strong in the right eye and milder in the left eye.
Here’s a breakdown of each part:
- OD (Oculus Dexter) = Right eye
- OS (Oculus Sinister) = Left eye
Right eye (OD):
-
SPH (Sphere): -4.50
This means moderate nearsightedness. Without glasses, distant objects appear blurry. The negative sign (-) indicates correction for myopia. -4.50 diopters is considered moderate myopia. -
CYL (Cylinder): -1.25
This corrects astigmatism (irregular corneal shape causing blurred or distorted vision at all distances). The value -1.25 is a mild-to-moderate amount of astigmatism. -
Axis: 176
This number (from 1 to 180) shows the orientation (angle) of the astigmatism correction. 176° is very close to 180°, meaning the main meridian of astigmatism runs almost horizontally.
Left eye (OS):
-
SPH (Sphere): -2.25
This indicates mild-to-moderate nearsightedness. Distant vision is blurry but less severely than the right eye. -
CYL (Cylinder): -1.25
Same amount of astigmatism correction as the right eye (mild-to-moderate). -
Axis: 12
The astigmatism correction is oriented at 12°, which is close to vertical (near the 0°/180° line but tilted slightly).
PD (Pupillary Distance): 70.5 mm
This is the distance between the centers of your pupils. 70.5 mm is slightly above average for adults (typical range is 54–74 mm). Accurate PD ensures the optical centers of the lenses align properly with your pupils, improving comfort and clarity.
Summary of what this prescription means overall:
You are nearsighted (myopic) in both eyes, with the right eye needing stronger distance correction. Both eyes also have astigmatism of the same power (-1.25 D), but oriented in very different directions (almost horizontal in the right eye, almost vertical in the left eye). This is a common and correctable prescription with glasses or contact lenses.
No “ADD” power is listed, so this prescription is for distance vision only (not including reading/bifocal/progressive addition for presbyopia).
References:
- https://www.aao.org/eye-health/glasses-contacts/how-to-read-eyeglasses-prescription
- https://www.warbyparker.com/learn/how-to-read-eye-prescription
- https://www.zennioptical.com/blog/how-to-read-your-eye-prescription