1. What is Lens Edge Thickness?

Lens edge thickness is the measurement from the front to the back surface of a lens at its thickest edge point. It's an important factor in eyewear design and comfort, especially for high-prescription lenses.

2. How Does the Calculator Work?

The calculator uses the simple formula:

Where:

• Center Thickness — The thickness of the lens at its center (mm)
• Sagitta — The height difference between the lens edge and the vertex (mm)

Explanation: The edge thickness is determined by adding the center thickness to the sagittal depth of the lens curve.

3. Importance of Edge Thickness Calculation

Details: Proper edge thickness ensures comfortable eyewear that fits well in frames. Thicker edges may require special frame selection or lens thinning techniques.

4. Using the Calculator

Tips: Enter center thickness and sagitta values in millimeters. Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical edge thickness for glasses?
A: Standard lenses typically have edge thickness between 2-5mm, while high-index or high-prescription lenses may be thicker.

Q2: How can I reduce edge thickness?
A: Using higher index materials, aspheric designs, or smaller frames can reduce edge thickness.

Q3: What is the relationship between prescription and edge thickness?
A: Stronger prescriptions (especially minus powers) generally result in thicker edges unless special thinning techniques are used.

Q4: Does frame shape affect edge thickness?
A: Yes, larger frames and rounder shapes typically result in thicker edges for the same prescription.

Q5: What's the minimum edge thickness for safety?
A: Most safety standards recommend at least 1mm edge thickness for impact resistance.