You may not need the thinnest lens automatically. For minus prescriptions, lens edge thickness depends on prescription strength, frame size, lens shape and final basket cost.
For mild minus prescriptions, standard or 1.6 lenses may be enough. For stronger minus prescriptions, compare 1.67 and 1.74 with frame size and finished basket price. Ask for advice if the prescription or frame choice is complex.
| Prescription and frame situation | Often worth comparing | Safer route |
|---|---|---|
| Mild minus, small frame | Standard or 1.6 | Online can be reasonable if measurements are clear. |
| Moderate minus, medium frame | 1.6 and 1.67 | Compare finished basket price and coatings. |
| Strong minus, larger frame | 1.67 and 1.74 plus smaller frames | Ask retailer or optician about suitability. |
Minus prescriptions usually get thicker at the lens edge. Higher-index lenses can reduce that edge thickness, but prescription strength is not the only factor. A smaller, rounder frame may do more for thickness than paying for the highest index in a large frame.
Minus lenses are designed differently from plus lenses and tend to be thicker toward the edge. The wider the lens area, the more edge thickness can show. That is why frame width, lens shape and how well your pupils sit within the frame all matter.
| Standard / 1.5 | Usually the lowest-cost choice for mild minus prescriptions. |
|---|---|
| 1.6 | A modest thinning comparison for buyers who want a neater lens without premium cost. |
| 1.67 | Often worth comparing when minus strength or frame size makes edge thickness more noticeable. |
| 1.74 | A premium comparison for stronger prescriptions, but not automatically needed or best value. |
A buyer with a moderate minus prescription in a large square frame may see more edge thickness than a buyer with a stronger prescription in a smaller round frame. Do not choose lens index from the prescription number alone. Compare prescription, frame size, lens shape, PD and budget together.
| Situation | What to compare | Why |
|---|---|---|
| Small round frame, mild minus | Standard vs 1.6 | Frame already controls thickness fairly well. |
| Medium frame, moderate minus | 1.6 vs 1.67 | Balance thickness improvement against price. |
| Large frame, stronger minus | Smaller frame plus 1.67/1.74 | Changing frame may be as important as lens index. |
| Unclear prescription or prism | Optician or supported retailer route | Lens choice becomes a fitting and dispensing question. |
Yes. Minus lenses are usually thicker toward the edge, and larger frames can make this more noticeable.
No. It can reduce thickness for some orders, but it may not be necessary or best value for every prescription and frame.
Yes. Smaller, rounder and well-centred frames can help many minus-prescription buyers.
Be cautious with stronger minus prescriptions and ask about suitability before choosing rimless or semi-rimless frames.
Use retailer support or a qualified optician if the prescription is strong, includes prism, or the frame choice is uncertain.
Checked 6 May 2026 using UK Glasses Guide lens-index guidance, NHS prescription information and College of Optometrists spectacle sale/supply guidance. This page avoids hard clinical thresholds because suitability depends on prescription, frame and fitting.