Choose 1.67 for the best overall balance
It is often an excellent choice when you need a thin lens but do not expect the small additional reduction from 1.74 to change how the glasses look or feel.
Eyewear Advice · Lens Materials & Design
1.74 is thinner than 1.67—but not always enough to make it the better lens.
For a prescription that truly benefits from maximum thickness reduction, 1.74 can be worth it. For many strong prescriptions, 1.67 gives a better balance of thinness, optical performance, availability, and cost. The frame often changes the answer more than the index number.
The Short Answer
Choose 1.74 only when the extra thickness reduction will be meaningful.
1.74 high-index material bends light more efficiently than 1.67, so it can usually make the same prescription a little thinner. It is most useful when a strong prescription, larger lens shape, or cosmetic priority makes every bit of thickness reduction valuable.
1.67 is often the more balanced choice. It can already make strong prescriptions substantially thinner than standard plastic while usually offering broader lens-design availability and a lower price than 1.74.
Side-by-Side Comparison
The higher number wins on thinness—not necessarily on the complete pair.
| Question | 1.67 high-index | 1.74 high-index |
|---|---|---|
| Which is thinner? | Very thin for many moderate-to-strong prescriptions | Usually the thinner option when all other variables match |
| Which is lighter? | Often competitive because the material is less dense | Not automatically lighter, even when it is thinner |
| Optical tradeoffs | Often a better balance of thinness and chromatic dispersion | Material-dependent dispersion may be more noticeable to sensitive wearers |
| Availability | Commonly offered in a broad range of designs and treatments | Some designs, prescriptions, tints, or treatments may be limited |
| Cost | Usually the lower-cost choice | Usually carries a premium for the final increment of thinness |
| Best use | Strong prescriptions that need thinness without maximizing index | Very strong prescriptions or situations where maximum thinness has real value |
These are general tendencies. The exact result depends on the specific material, prescription, lens design, frame, measurements, treatments, and laboratory processing.
The Difference Is Usually Modest
Going from 1.67 to 1.74 is a refinement, not a dramatic transformation.
The extra thinness can be worthwhile in the right prescription, but marketing images often exaggerate the difference. Ask for a thickness estimate using your actual prescription and frame before paying more.
When Each One Makes Sense
Start with the finished result you care about.
Choose 1.74 when every millimeter matters
It can be worthwhile for very strong prescriptions, especially when visible edge or center thickness remains a concern after the frame has been optimized.
Choose neither when another priority leads
Impact needs, drilled or grooved frames, optical sensitivity, specialized lens designs, and budget may point to a different material altogether.
The Frame Comes First
A better frame choice can save more thickness than moving from 1.67 to 1.74.
Strong minus lenses are thickest at the edges. A smaller eye size, a shape without long corners, and pupils positioned near the optical center reduce how much of the thick outer lens remains.
Strong plus lenses are thickest in the center. Frame size, lens design, required center thickness, and how the frame holds the lens all influence the final profile. In either case, compare materials only after selecting an appropriate frame.
Clarity and Color Dispersion
Refractive index is not an optical-quality score.
Higher-index materials tend to have lower Abbe values, which means more chromatic dispersion away from the optical center. Some wearers notice colored fringes or a less comfortable peripheral view; many do not.
Prescription, lens design, accurate measurements, frame position, and the wearer's sensitivity all affect the experience. The highest index is not automatically the clearest lens.
What to Compare Before Ordering
Ask for more than the material number.
Estimated thickness
Compare realistic center or edge thickness in the exact frame, not a generic sample lens.
Finished weight
Material density, lens diameter, frame weight, and remaining lens volume all contribute.
Design availability
Confirm that the preferred single-vision, progressive, occupational, or specialty design is offered in the material.
Coating quality
High-index lenses benefit from a durable anti-reflective treatment because their surfaces reflect more light.
Related Guidance
Build the frame and lens plan together.
Technical References
Material properties guide the estimate; your prescription and frame decide the result.
Published data confirms that 1.67 and 1.74 are high-index options and that higher-index materials can reduce thickness. It also shows why dispersion, density, design, and frame geometry must be considered alongside index.
Review high-powered lens thickness and optics ↗Review high-index material availability ↗
1.67 vs. 1.74 FAQ
Thinness, weight, clarity, prescriptions, and coatings.
Are 1.74 lenses thinner than 1.67 lenses?
Usually, yes. With the same prescription, frame, measurements, design, and minimum thickness, 1.74 material can produce a thinner lens than 1.67. The difference is often modest, and frame size or eye position may change the finished thickness more.
Is 1.74 always better than 1.67?
No. A 1.74 lens may be worthwhile when a strong prescription will gain a visible thickness benefit. For many prescriptions, 1.67 provides a better balance of thinness, optical performance, availability, and cost.
Are 1.74 lenses lighter than 1.67 lenses?
Not automatically. Higher-index materials are often denser. Although 1.74 may use less material, the finished lens is not guaranteed to weigh less. Frame size, prescription, design, and minimum thickness all affect weight.
Which index is better for a strong minus prescription?
Both may be appropriate. A compact frame with the pupils well centered is usually the first step. Then 1.74 may provide an additional edge-thickness benefit when the prescription is strong enough; otherwise 1.67 may be the more balanced choice.
Which index is better for a strong plus prescription?
The answer depends on prescription power, frame size, lens design, and the required center thickness. A higher index can reduce center thickness and curvature, but the difference should be calculated for the actual frame.
Do 1.67 and 1.74 lenses need anti-reflective coating?
A quality anti-reflective treatment is strongly worth considering for both. High-index materials reflect more light at their surfaces than standard plastic, so the treatment can improve lens appearance and light transmission.