Hi-Index 1.74
n 1.740- Center
- 1.50 mm
- Maximum edge
- 6.47 mm
Patient Resources
See How Lens Material Affects Thickness
What difference can a thinner lens material make for your prescription? Choose an example, select a frame size, and compare calculated lenses at the same scale.
Beta notice
Thickness evaluator in testing
This thickness evaluator is a beta tool and is subject to errors or misrepresentation. Results are educational estimates only and may not reflect the final manufactured lens.
Be advised: confirm all measurements, specifications, and finished-lens requirements with a qualified eye care professional or laboratory.
Step 1
Choose a sample prescription
Selected prescription
Sphere -6.00 D · Cylinder -1.50 D · Axis 180°
Rx default: 2.75 D using Vogel’s Rule. Your laboratory or lens manufacturer may specify a different curve.
Step 2
Choose a frame size
Choose the closest frame shape above. Open the dimensions only when you have the frame’s A, B, DBL, or optical-center height.
Optional frame analysisOpen frame fit map
Frame fit map
Right lens
Frame centerOptical center (green)Thickest edge (gold)
Why measurements matter
Proper decentration follows your pupils
PD places each lens’s optical center horizontally. Optical-center height places it vertically in the worn frame. Proper decentration means aligning those centers with your pupils—not simply centering them in the frame.
A frame whose geometric centers are closer to your measured PD and height generally needs less lens diameter. That can reduce unnecessary edge thickness, although prescription, lens design, and safety requirements still matter.
Current position
4.0 mm inward per eye and 1.0 mm higher
Hi-Index 1.67
7.07 mm estimated maximum edge
The green point is the optical center. The gold point marks the calculated thickest edge. Every change above recalculates the comparison below.
Step 3
Lens material comparison
See the thickness difference
Every lens uses the same prescription and frame, shown at one shared physical scale.
Visual thickness
Numeric and visual thickness are at actual relative scale.
Measured cross section
Thickest-edge meridian · Front base curve 2.75 D.
Hi-Index 1.74
Tokai 1.76Solid: front · dashed: back · fine dash: frame plane
Tokai 1.76Solid: front · dashed: back · fine dash: frame planeTokai 1.76
Estimated maximum edge: 5.83 mm
0.65 mm thinner than Hi-Index 1.74 in this scenario (10.0% reduction).
Tokai 1.76
n 1.760- Center
- 1.00 mm
- Maximum edge
- 5.83 mm
Why does index matter?
Higher-index materials bend light more efficiently. Depending on the prescription, frame, and design, that can reduce finished thickness.
Frame choice matters too
A smaller, well-centered frame often needs less lens diameter, which can reduce the thickest edge of a nearsighted lens.
Ask your eye care professional
The best choice also depends on visual needs, lens design, safety requirements, frame measurements, and professional recommendations.
Thickness estimate notice: Lens thickness can be influenced by additional specifications including base curve, lens design (such as spherical, aspheric, atoric, or free-form), minimum center or edge thickness, bevel placement, frame shape and fit, manufacturer requirements, and laboratory finishing tolerances. The values shown are educational estimates; actual finished lenses may differ.