1. What is Edge Thickness?

Edge thickness in spectacle lenses is the measurement from the front to the back surface at the edge of the lens. It's an important factor in lens cosmetics and frame selection.

2. How Does the Calculator Work?

The calculator uses the simple formula:

Where:

• \( Sagitta \) — The sagittal depth or vertex depth of the lens (mm)
• \( Minimum \) — The minimum center thickness required for the lens (mm)

Explanation: The edge thickness is determined by adding the sagitta (which represents the curvature of the lens) to the minimum center thickness required for structural integrity.

3. Importance of Edge Thickness Calculation

Details: Calculating edge thickness helps opticians select appropriate lenses for frames, ensuring proper fit and cosmesis. Thicker edges may require specific frame types or lens materials.

4. Using the Calculator

Tips: Enter sagitta and minimum thickness values in millimeters. Both values must be positive numbers. The calculator will sum these values to determine the edge thickness.

5. Frequently Asked Questions (FAQ)

Q1: What factors affect edge thickness?
A: Lens power, base curve, index of refraction, and minimum center thickness all contribute to edge thickness.

Q2: How can I reduce edge thickness?
A: Using higher index materials, aspheric designs, or adjusting the frame size can help reduce edge thickness.

Q3: What is a typical edge thickness range?
A: Standard lenses typically range from 2-8mm at the edge, depending on prescription and frame size.

Q4: Why is edge thickness important?
A: Excessive edge thickness can affect lens appearance, frame selection, and comfort.

Q5: Does edge thickness affect optical quality?
A: While edge thickness itself doesn't affect vision quality, very thick edges may cause distortion in peripheral vision.