1. What is Optical Lens Thickness?

Optical lens thickness is a critical parameter in optometry and lens manufacturing, calculated as the sum of the sagittal depth (Sag) and center thickness (CT) of the lens.

2. How Does the Calculator Work?

The calculator uses the simple formula:

Where:

• \( Sag \) — Sagittal depth (mm)
• \( CT \) — Center thickness (mm)

Explanation: The total thickness of an optical lens is determined by adding its sagittal depth (the vertical distance from the edge to the vertex) to its center thickness.

3. Importance of Lens Thickness Calculation

Details: Accurate thickness calculation is essential for lens design, fitting, and determining optical properties like weight, refractive index, and edge thickness.

4. Using the Calculator

Tips: Enter sagittal depth and center thickness in millimeters. Both values must be positive numbers for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is sagittal depth (Sag)?
A: Sagittal depth is the vertical distance from the lens edge to the vertex of the curved surface, measured along the optical axis.

Q2: What is center thickness (CT)?
A: Center thickness is the thickness of the lens at its thinnest point, typically at the optical center for spherical lenses.

Q3: Why is lens thickness important?
A: Lens thickness affects weight, comfort, optical performance, and cosmetic appearance of eyewear.

Q4: How does refractive index affect thickness?
A: Higher refractive index materials can achieve the same optical power with less thickness compared to standard materials.

Q5: What are typical thickness values?
A: Typical values vary by prescription, but standard lenses might have CT of 1.5-3.0mm and Sag of 1.0-5.0mm depending on base curve and diameter.