How to calculate the thickness of your prescription lenses
Optician's tips for choosing thinner, lighter lenses adapted to your prescription. The thickness of a lens depends on your correction, the refractive index, and the frame. Here's how to understand, compare, and optimize your choices for a comfortable and aesthetic result.
Prescription lenses: understanding thickness by index
For an identical prescription and equal effective diameter, a higher index reduces thickness by approximately 1 / n: the larger the index n, the thinner the lens can be while still bending light. Quick guide to intelligently choose the index according to your daily life and budget:
- Index 1.50 : standard for low corrections, economical and clear
- Index 1.60 : medium thinning, good weight/thickness compromise for daily use
- Index 1.67 : strong thinning suitable for medium to high corrections
- Index 1.74 : ultra-thin for high prescriptions or aesthetic constraints
At Visionet, we offer renowned resins: 1.50 Hard Resin, 1.60 MR-8, 1.67 MR-7, 1.74 MR-174, all compatible with premium surface treatments (anti-reflective, anti-smudge, hardened).
Myopia vs hyperopia: where is the thickness?
- Negative lenses (myopia) : thicker at the edges, thinner at the center
- Positive lenses (hyperopia) : thicker at the center, thinner at the edges
This difference dictates the choice of frame shape and lens size. The greater the ocular size and decentration, the greater the thickness. Hence the benefit of compact and well-centered frames.
Optimizing lens thickness: optician's advice
- Prefer a full-rim frame to hide the edges and secure the mounting
- Choose a small size and a balanced shape to limit the effective diameter
- Avoid extra-wide frames for strong prescriptions, especially for myopia
- Have pupillary distance and centering heights precisely measured to reduce decentration
- Add treatments like anti-reflective, hardened anti-scratch, and anti-smudge for lasting comfort
Simulate your lens thickness online
A thickness simulator allows you to compare, as an indication, the rendering of indices according to your prescription. Enter your sphere/cylinder powers, lens size, and test several indices to visualize the difference between 1.50 (Hard Resin), 1.60 (MR-8), 1.67 (MR-7), and 1.74 (MR-174). Results vary depending on the frame and measurements taken — our opticians then validate the best option for your case.
Choosing the index according to your prescription
Low corrections (≈ |Sph| < 2.00 D)
1.50 is often suitable if the frame is compact and well-centered. Opt for 1.60 if you prefer a thinner and lighter result or if the frame is a bit wide.
Medium corrections (≈ 2.00 to 4.00 D)
1.60 is an excellent compromise. For thin frames or large eyes, go up to 1.67 to maintain a good aesthetic, especially for myopia.
Strong corrections (> 4.00–5.00 D)
1.67 is often recommended, 1.74 to maximize thinning if the frame is wide or if aesthetic requirements are a priority. A small, full-rim frame remains the best ally.
Frames: shapes, rimming, and materials
- Shapes : moderate rectangles, not too wide rounds/ovals, avoid large lenses for myopia
- Rimming : full-rim helps hide thickness, semi-rimless and rimless require higher indices and careful mounting
- Materials : acetate to wrap the edges, thin metal for lightness with thinned lenses
Why is thickness important?
Thinner lenses improve comfort (reduced weight), aesthetics (discreet profile), and mounting stability. Add appropriate treatments to preserve transparency and facilitate daily maintenance.
Need personalized help?
Our qualified opticians analyze your prescription, habits, and frame to recommend the most relevant index, treatments, and mounting. Contact us for tailored support.
Updated on — Editorial : Visionet.
