Contact Lens Size Guide
Find your perfect contact lens fit with our comprehensive size guide. Learn how to measure your eyes and understand contact lens specifications.
Understanding Eye Measurements
Anatomy of the human eye showing key measurement points
Key Measurements
- Corneal Diameter: 11.5-12.5mm (average)
- Pupil Size: 2-8mm (varies with light)
- Corneal Curvature: 7.8-8.8mm (base curve)
- Visible Iris Diameter: 11-13mm
Contact Lens Size Chart
| Parameter | Measurement | Typical Range | Description |
|---|---|---|---|
| Base Curve (BC) | 8.4mm - 8.8mm | 8.0mm - 9.2mm | Curvature matching your cornea |
| Diameter (DIA) | 13.8mm - 14.5mm | 13.0mm - 15.0mm | Width of the contact lens |
| Center Thickness | 0.04mm - 0.20mm | 0.03mm - 0.30mm | Lens thickness at center |
| Edge Thickness | 0.10mm - 0.30mm | 0.08mm - 0.40mm | Lens thickness at edge |
| Optical Zone | 6.0mm - 8.5mm | 5.5mm - 9.0mm | Clear vision area |
How to Measure Your Eyes
Step 1: Measure Corneal Diameter
Use a ruler or caliper to measure the horizontal diameter of your cornea (white-to-white distance). This helps determine the appropriate lens diameter.
Step 2: Determine Base Curve
Your eye doctor will measure your corneal curvature using a keratometer. This determines the base curve (BC) of your contact lenses.
Typical Base Curve Values:
- Steep cornea: 8.0-8.3mm
- Average cornea: 8.4-8.6mm
- Flat cornea: 8.7-9.0mm
Step 3: Check Pupil Size
Pupil size affects lens selection, especially for multifocal or toric lenses. Measure in normal room lighting.
Brand-Specific Size Guide
Acuvue
- Oasys: BC 8.4/8.8, DIA 14.0mm
- Moist: BC 8.5/9.0, DIA 14.2mm
- 1-Day: BC 8.5/9.0, DIA 14.2mm
Air Optix
- Plus Hydraglyde: BC 8.6, DIA 14.2mm
- Aqua: BC 8.4/8.6, DIA 14.2mm
- Colors: BC 8.6, DIA 14.2mm
Fitting Tips & Troubleshooting
Good Fit Signs
- Comfortable wear all day
- Clear vision without blurriness
- Lens stays centered on eye
- No excessive movement when blinking
- No redness or irritation
Poor Fit Signs
- Discomfort or pain
- Blurred or fluctuating vision
- Lens moves excessively
- Redness or irritation
- Lens falls out easily
Measurement Tools & Resources
Size Calculator
Online tool to estimate your lens size
Frequently Asked Questions
Too small lenses can cause discomfort, poor vision, and may fall out easily. They might also restrict oxygen flow to your cornea.
While you can get rough estimates, professional measurement by an eye doctor is essential for accurate sizing and safe lens wear.
You should have your eyes measured annually or whenever you experience discomfort with your current lenses.
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