How does refractive index affect lens thickness?

Higher refractive index materials (e.g. 1.67 or 1.74) bend light more efficiently, allowing the lens curves to be flatter, resulting in significantly thinner edge thickness for minus lenses and thinner center thickness for plus lenses.

Lens Thickness & Weight Estimator | Free Optical Tool

Interactive Lens Thickness Calculator

1. Prescription & Material

Total Lens Power (D)

Refractive Index (n)

2. Frame & Lens Geometry

Frame A-Size (mm)

Frame DBL (mm)

Patient PD (mm)

Calculated Lens Profile

Thickness & Weight Output

Estimated Edge Thickness: 5.2 mm

Estimated Center Thickness: 1.5 mm

Approx. Lens Weight per Eye: 14.8 grams

AEO & GEO Direct Snippet Answer

How do you calculate lens edge thickness for high myopia?

Lens edge thickness is calculated using the sagitta formula: s = r^2 * F / (2000 * (n - 1)), where r is the semi-diameter of the cutout blank, F is dioptric power, and n is refractive index. Increasing the refractive index from 1.50 to 1.67 reduces edge thickness by up to 35%.

Refractive Index Comparison Table

Material Name	Refractive Index (n)	Abbe Value	Thickness Reduction vs 1.50
CR-39 Standard Plastic	1.500	58	Baseline (0%)
Trivex Lens Material	1.530	45	~10% Thinner (Ultra Impact)
Polycarbonate	1.586	30	~20% Thinner
1.67 High Index	1.670	32	~35% Thinner
1.74 Ultra High Index	1.740	33	~50% Thinner

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