Understand 1.56, 1.60, 1.67 and 1.74 high-index spectacle lenses, how much thickness they can save, what frame choice changes, and how to choose the right index without overpaying.
A higher refractive index can make the same prescription thinner, but the highest index is not automatically the best choice. Your prescription, frame size, pupil position, lens design, coating, weight and budget all influence the finished result.
What Are High-Index Lenses?
High-index lenses are spectacle lenses made from materials that bend light more efficiently than standard plastic. Because the material has a higher refractive index, the required prescription can usually be produced with less lens curvature and less material thickness.
For someone with a stronger prescription, this can make spectacles look noticeably slimmer. The benefit is primarily cosmetic and practical: less edge bulk in minus prescriptions, less centre bulk in plus prescriptions, and often a more balanced finished pair of glasses.
What Do 1.56, 1.60, 1.67 and 1.74 Mean?
These numbers describe the refractive index of the lens material. A material with a higher index bends light more strongly. All other things being equal, that allows a stronger prescription to be made thinner.
| Lens index | General role | Typical reason to consider it | What to keep in mind |
|---|---|---|---|
| 1.50 / standard plastic | Basic standard lens | Lower prescriptions and value-focused eyewear | Can become bulky as prescription increases |
| 1.56 | Entry-level thinner material | Mild to moderate prescriptions where some thickness reduction is useful | The visible difference may be modest in low powers |
| 1.60 | Balanced thin-lens option | Moderate prescriptions, thinner appearance and good everyday value | Often a practical middle ground |
| 1.67 | High-index lens | Stronger prescriptions where edge or centre thickness is becoming noticeable | Good anti-reflective coating is strongly worth considering |
| 1.74 | Ultra-high-index lens | Very strong prescriptions where maximum practical thinness is a priority | Higher price and not always necessary for moderate powers |
Why Do Strong Prescriptions Look Thick?
Minus prescriptions
Minus lenses are thinner in the centre and thicker toward the edge. As minus power increases, edge thickness becomes more noticeable—especially in large or wide frames.
Plus prescriptions
Plus lenses are thicker in the centre. Stronger plus prescriptions may look more curved and can magnify the appearance of the eyes. A higher-index material, a smaller frame and an appropriate aspheric design can help reduce bulk.
Astigmatism also matters. Significant cylinder power can make thickness vary around the lens depending on the axis, which is another reason a single “power-to-index” chart cannot predict the final result perfectly.
Who Should Consider High-Index Lenses?
High-index lenses are most useful when standard lenses would otherwise become noticeably thick or heavy. They may be worth discussing if you have a moderate-to-strong prescription, dislike visible lens edges, want a more refined cosmetic result or are choosing a frame where lens thickness will be exposed.
- Moderate or high minus prescriptions where edge thickness is visible.
- Moderate or high plus prescriptions where centre thickness is significant.
- Strong astigmatism where thickness varies around the lens.
- Customers who want a slimmer finished profile.
- Progressive-lens wearers with stronger prescriptions.
- Customers choosing premium frames where lens aesthetics matter.
For low prescriptions, high-index material may provide little visible benefit. In that situation, money may be better spent on a better coating, a better lens design or a better-fitting frame.
Does Frame Choice Affect Lens Thickness? A Lot.
Frame selection is one of the most overlooked parts of thin-lens dispensing. In many higher minus prescriptions, a smaller frame with the pupil positioned close to the optical centre can reduce visible edge thickness dramatically. A very large frame increases the distance from the pupil to the outer edge, forcing the lens to extend farther into its thickest area.
Frames that often help strong prescriptions
- Smaller lens shapes and moderate eye sizes.
- Round or softly oval shapes that keep corners closer to the pupil.
- Frames with good pupil centration.
- Full-rim frames that can visually conceal some edge thickness.
Frames that may increase visible thickness
- Oversized frames.
- Very wide rectangular shapes.
- Frames where your pupils sit far inward from the geometric centre.
- Large fashion shapes with long outer corners.
Read our guide to choosing frames for high-power prescriptions if frame selection is as important to you as lens thinness.
Which High-Index Lens Should I Choose?
The best index is the one that provides a meaningful improvement without paying for thinness you will barely notice. The illustration below is a simple educational guide—not a prescription rule.
1.56 lenses
1.56 can be a sensible entry-level thinner lens for mild to moderate prescriptions. It may provide a small cosmetic improvement over standard plastic without moving into premium high-index pricing.
1.60 lenses
1.60 is often a strong balance of thickness, optical performance and price. For many moderate prescriptions, it can deliver a noticeable improvement while avoiding the cost of 1.67 or 1.74.
1.67 lenses
1.67 becomes particularly useful when edge or centre thickness is clearly visible. It is frequently considered for stronger prescriptions and customers who place a high value on a slimmer appearance.
1.74 lenses
1.74 is among the thinnest commonly available plastic lens materials. It can be worthwhile for very strong prescriptions, but the extra cost does not automatically produce a dramatic difference in every frame. A small, well-chosen frame with 1.67 can sometimes be a better overall decision than a very large frame with 1.74.
Do High-Index Lenses Need Anti-Glare Coating?
Anti-reflective coating is particularly valuable on high-index lenses. As refractive index increases, surface reflections can become more noticeable. A good anti-reflective coating can improve cosmetic appearance and allow more light to pass through the lens rather than reflecting off its surfaces.
When comparing high-index quotations, do not compare index alone. Ask what coating is included and whether it provides scratch resistance, easier cleaning, water repellence or other practical features.
For a deeper explanation, see our Anti-Glare & Lens Coatings guide.
Does a Higher Index Always Mean Better Optical Quality?
No. Higher index mainly describes the material’s ability to bend light. It does not automatically mean sharper vision.
Lens materials also differ in properties such as Abbe value, density, reflectivity and impact characteristics. Some higher-index materials can show more colour fringing away from the optical centre than materials with higher Abbe values. In practice, good centration, an accurate prescription, a suitable lens design and correct fitting can matter as much as the index itself.
Aspheric and atoric lens designs
For certain prescriptions, an aspheric or atoric design can further improve appearance and peripheral optics. These designs can flatten the lens profile and are especially relevant in stronger plus powers, higher prescriptions and some astigmatic prescriptions.
High index does not guarantee lighter weight
Thinner does not always mean proportionally lighter. Different lens materials have different densities, and the finished weight also depends on frame size. A smaller 1.60 lens may sometimes feel lighter than a much larger 1.74 lens.
Are High-Index Lenses Worth the Extra Cost?
They can be excellent value when the prescription is strong enough for the thickness reduction to be visible. They are less compelling when the prescription is low or the frame is already small enough that a standard material will look thin.
What Determines Final Lens Thickness?
Your prescription is only one part of the equation. The finished lens thickness can be influenced by:
- Sphere power.
- Cylinder power and axis.
- Lens index.
- Frame eye size and shape.
- Your pupillary distance and how much the lens must be decentered.
- Minimum centre or edge thickness required by the lens and frame.
- Lens design, including spherical, aspheric or atoric design.
- Progressive-lens design where applicable.
High-Index Lenses and Progressive Lenses
High-index materials can be combined with progressive lens designs. For a progressive wearer with a stronger prescription, choosing the correct material can improve the finished appearance and reduce bulk. However, the progressive design, fitting height, pupil measurements and frame fit remain critical to visual comfort.
See our Progressive Lenses guide for more detail on design and adaptation.
Are High-Index Lenses Suitable for Rimless Frames?
Sometimes, but index alone should not determine the answer. Rimless and drilled frames place mechanical stress around mounting points. Material toughness, thickness, lens shape and the manufacturer’s recommendations should all be considered. In some prescriptions, another lens material may be preferred even if it is not the highest index.
High-Index Lens Buying Checklist
Before ordering, ask your optician:
- Which index is appropriate for my exact prescription?
- How much thinner will 1.67 be than 1.60 in this specific frame?
- Would a smaller frame make a bigger difference than moving to a higher index?
- What anti-reflective coating is included?
- Is the lens spherical, aspheric or atoric?
- What will the approximate edge or centre thickness be?
- Is 1.74 giving me a meaningful benefit or mainly increasing the price?
- What warranty applies to the lens and coating?
Frequently Asked Questions About High-Index Lenses
What are high-index spectacle lenses?
High-index lenses are made from materials that bend light more efficiently than standard plastic. This allows many prescriptions to be produced with less lens thickness.
Are 1.67 lenses thinner than 1.60 lenses?
Usually yes when the prescription, frame and lens design are the same. The visible difference varies with the actual prescription and frame dimensions.
Is 1.74 always thinner than 1.67?
For the same prescription and geometry, 1.74 can generally be made thinner. However, the real-world improvement may be small in some prescriptions, so 1.67 can sometimes offer better value.
Which index is best for a high prescription?
There is no universal cutoff. Stronger prescriptions often benefit from 1.67 or 1.74, but frame size, astigmatism, pupil position and cosmetic expectations must also be considered.
Do I need high-index lenses for a low prescription?
Usually not for thickness alone. If a standard lens will already be thin, upgrading the index may provide little visible benefit.
Are high-index lenses lighter?
They can reduce the amount of lens material, but different materials have different densities. Final weight depends on both the material and the overall lens size.
Why do high-index lenses need anti-reflective coating?
Higher-index materials can produce more surface reflections. A good anti-reflective coating improves transparency and cosmetic appearance and is generally a worthwhile pairing with high-index lenses.
Are high-index lenses good for computer use?
Lens index mainly affects thickness. Computer comfort depends more on the correct prescription, working distance, lens design and anti-reflective performance.
Can high-index lenses reduce the “small eyes” look in minus prescriptions?
A thinner lens and a smaller, well-centred frame can improve overall cosmetics, but the apparent eye-size effect is also influenced by prescription power and lens-to-eye distance.
Can high-index lenses reduce magnification in plus prescriptions?
A thinner, flatter aspheric high-index design and suitable frame can improve cosmetic appearance, although the prescription itself still creates magnification.
Which frame is best for strong minus lenses?
Smaller, well-centred, rounder or softly oval full-rim frames often help keep edge thickness under control. Oversized frames tend to increase visible edge thickness.
Are 1.74 lenses worth the extra money?
They can be worth it for very strong prescriptions where maximum practical thinness matters. For moderate prescriptions, 1.60 or 1.67 may offer better value.
Do high-index lenses scratch more easily?
Scratch performance depends heavily on the hard coating and how the lenses are cared for. No spectacle lens should be considered completely scratch-proof.
Are high-index lenses suitable for rimless glasses?
They can be in some cases, but suitability depends on the exact material, lens thickness, drilling requirements and frame construction. Index alone is not enough to decide.
What is the difference between high-index and blue-filter lenses?
High index describes the lens material and mainly affects thickness. Blue filtering is a separate feature or technology related to selected wavelengths of visible light.
Can progressive lenses be made in 1.67 or 1.74?
Yes, many progressive designs are available in high-index materials. Availability varies by lens manufacturer, design and prescription range.
How can I know how thick my finished lenses will be?
An optician can estimate thickness using your full prescription, pupil measurements, frame dimensions, lens material and minimum thickness requirements. This is more useful than choosing an index from power alone.
