Understanding your contact lens prescription is essential for ordering the right lenses. This guide explains all the parameters on your prescription.
Prescription Parameters Explained
SPH / Power (PWR)
What it is: The refractive power of the lens in diopters (D)
Range: Typically -0.50 to -10.00 (myopia/nearsighted) or +0.50 to +6.00 (hyperopia/farsighted)
Negative (-): Corrects nearsightedness (can see close, not far)
Positive (+): Corrects farsightedness (can see far, not close)
CYL (Cylinder)
What it is: Amount of lens power for astigmatism correction
Range: Typically -0.75 to -2.75
Note: Not all contact lenses have CYL. Standard soft lenses may not correct astigmatism.
AXIS
What it is: The orientation of the cylinder power in degrees
Range: 1 to 180 degrees
Note: Only appears if you have CYL (astigmatism)
BC (Base Curve)
What it is: The curvature of the lens back surface
Range: 8.3mm to 9.0mm for soft lenses
Importance: Determines how the lens fits on your eye
DIA (Diameter)
What it is: Total width of the lens
Range: 13.8mm to 15.0mm
Importance: Affects coverage and appearance
Sample Prescription
| Parameter | Right Eye (OD) | Left Eye (OS) |
|---|---|---|
| SPH/PWR | -3.50 | -3.75 |
| CYL | -0.75 | -0.75 |
| AXIS | 180 | 175 |
| BC | 8.6 | 8.6 |
| DIA | 14.2 | 14.2 |
Important Notes
❌ Glasses Prescription ≠ Contact Lens Prescription
Glasses sit 12mm from your eyes, contacts sit directly on the eye. Powers may differ, especially for high prescriptions (±4.00D or more).
✅ Always Get a Contact Lens Fitting
An optometrist must fit you for contacts. They will determine the correct BC, DIA, and verify the power works on your eye.
⚠️ Prescription Expiration
Contact lens prescriptions typically expire in 1-2 years. You need a new exam to renew.
For Brand Owners
When selling contact lenses:
- Clearly display all parameters (PWR, BC, DIA)
- Require prescription verification where legally required
- Educate customers on their prescription parameters
- Offer a range of powers (typically -0.50 to -8.00 for color lenses)
At MIOMI Optical
We offer:
- Power range: 0.00, -0.50 to -8.00 (custom powers available)
- BC options: 8.4mm, 8.6mm, 8.8mm
- DIA options: 14.0mm, 14.2mm, 14.5mm
- Documentation: All parameters clearly labeled
Contact us: eye@miomi.cc | miomicon.com
