HIGH-INDEX LENS COMPARISON
Both 1.67 and 1.74 are premium high-index materials designed to reduce lens bulk in stronger prescriptions. The better choice depends on your prescription, frame dimensions, measurements, and how strongly you prioritize the thinnest possible finished lens.
Keep your current frames when compatible. Final lens thickness depends on your complete prescription and frame measurements.
THE FASTEST WAY TO CHOOSE
The strongest choice is not automatically the highest refractive index. Start with your prescription and frame, then decide how important maximum thinness is to you.
1.67 is already a premium high-index lens. For many strong prescriptions, it provides a meaningful reduction in lens thickness without requiring the highest index available.
1.74 is most compelling when visible lens bulk is a major concern and you want the highest-index clear plastic option available from RenewLens.
SIDE-BY-SIDE COMPARISON
A higher refractive index allows a lens material to bend light more efficiently. In suitable prescriptions, this can reduce the amount of lens material required and help produce a thinner finished lens.
| Comparison Point | 1.67 High-Index | 1.74 High-Index |
|---|---|---|
| Main advantage | Premium thinness with a strong overall balance | Greater thinness potential when every millimeter matters |
| Typical fit | Many moderately strong to strong prescriptions | Higher prescriptions or maximum-thinness goals |
| Frame consideration | Often excellent in moderate-size, well-centered frames | Worth stronger consideration when a larger frame may exaggerate thickness |
| Appearance | Very thin compared with lower-index materials for suitable prescriptions | Usually thinner than 1.67 when prescription and frame conditions are comparable |
| Finished weight | Can reduce lens bulk versus thicker lower-index options | Do not assume it is always lighter; finished weight also depends on density and lens geometry |
| Best decision logic | Choose when 1.67 already delivers the thinness you want | Choose when extra thickness reduction is genuinely important |
Illustration only—not an exact millimeter or percentage measurement. Actual finished thickness depends on the full prescription, PD, frame dimensions, lens shape, design, and minimum-thickness requirements.
THICKNESS DIFFERENCE
This is one of the most important questions when comparing 1.67 vs 1.74 high-index lenses. The answer is that 1.74 has greater thinness potential, but there is no single millimeter or percentage difference that applies to every prescription.
When the same prescription, frame, and lens design are compared, 1.74 can usually be made thinner than 1.67 because its higher refractive index bends light more efficiently. However, the actual thickness difference between 1.67 and 1.74 lenses depends on the complete prescription and frame.
The stronger the prescription, the more meaningful the additional thickness reduction from 1.74 may become. With some prescriptions, the visible difference between 1.67 and 1.74 may be relatively modest.
Frame width, lens shape, and optical positioning influence how much material is required. A smaller, well-centered frame may already produce an excellent result with 1.67.
Choosing 1.74 solely because the index number is higher is not always necessary. The goal should be the best balance of thickness, appearance, frame compatibility, and cost for your prescription.
Compare common prescription lens materials and learn how prescription, frame dimensions, and optical measurements affect finished thickness.
INDEX IS ONLY PART OF THE RESULT
Two customers can choose the same lens index and still receive noticeably different finished thicknesses. The material must be considered together with the prescription and frame.
Stronger prescriptions generally create more lens thickness. Astigmatism can also change where thickness appears around the lens.
Larger lens openings generally require more material. A smaller, well-centered frame can sometimes reduce thickness substantially.
The relationship between your pupillary distance and the frame can affect how far the optical center must be shifted and how thick the lens becomes.
Minus lenses are generally thicker toward the edges, while plus lenses are generally thicker through the center.
Base curve, lens design, and required minimum center or edge thickness influence the final geometry.
Full-rim, semi-rimless, rimless, grooved, and drilled frames can have different thickness and material requirements.
Review the RenewLens lens thickness guide for a broader comparison of common material options.
YOUR PRESCRIPTION SIGN MATTERS
Nearsighted prescriptions are generally thinner through the center and thicker toward the edge. Higher-index material and appropriate frame dimensions can both help reduce visible edge bulk.
Farsighted prescriptions are generally thicker through the center. High-index material, lens design, and frame size can help manage the finished center thickness.
This is one reason prescription strength alone cannot predict exactly how a finished pair of lenses will look. Frame size, PD, cylinder, lens diameter, and design can materially change the result.
DO NOT CHOOSE BY INDEX NUMBER ALONE
No. 1.74 has a higher refractive index and greater potential to reduce thickness, but that does not mean every prescription or frame needs it.
The better goal is to choose the material that produces the right finished pair of glasses—not simply the highest number.
COST VS THINNESS
For many prescriptions, 1.67 offers an excellent balance of thinness and value. Moving to 1.74 makes the most sense when reducing visible lens thickness is important enough to justify the additional upgrade cost.
1.67 is already a premium high-index material and can produce an excellent cosmetic result for many stronger prescriptions.
The additional cost of 1.74 is easier to justify when your prescription and frame can benefit from further thickness reduction and visible lens bulk is one of your main concerns.
KEEP THE FRAMES YOU ALREADY LIKE
Many existing frames can receive new high-index prescription lenses when the frame remains structurally sound and is compatible with the selected prescription, material, lens design, and mounting requirements.
Many full-rim frames can accept high-index lenses when the eyewire, bridge, hinges, and frame material remain stable.
Drill points, grooves, cords, edge thickness, and material suitability require additional attention.
Cracked, brittle, warped, heavily worn, or unstable frames may require additional review or may not be suitable for new lenses.
HOW THE RENEWLENS PROCESS WORKS
Select single vision, progressive, computer, professional, or sunglass lenses.
Compare available lens materials and choose the index that fits your prescription and goals.
Use your own secure box with the prepaid label or select the available free shipping-kit option.
Compatible frames are fitted with the new prescription lenses, inspected, packed, and returned with tracking.
READY TO ORDER?
A premium high-index option for many stronger prescriptions when you want meaningful thickness reduction without automatically choosing the highest refractive index.
Select 1.67 LensesThe highest-index clear plastic option currently offered by RenewLens for customers who place the greatest emphasis on reducing visible lens bulk.
Select 1.74 LensesRELATED RENEWLENS GUIDES
FREQUENTLY ASKED QUESTIONS
There is no universal millimeter or percentage difference because finished thickness depends on the complete prescription, frame dimensions, PD, lens shape, and lens design. Under otherwise comparable conditions, 1.74 has greater thickness-reduction potential than 1.67. The difference tends to matter more when the prescription or frame would otherwise produce substantial lens thickness.
It depends on how much additional thickness reduction matters for your prescription and frame. 1.67 already provides excellent thinness for many stronger prescriptions. 1.74 is most compelling when maximum practical thickness reduction is a priority and your prescription and frame can meaningfully benefit from the higher index.
Both are high-index lens materials. 1.74 has a higher refractive index, giving it greater potential to reduce finished lens thickness when the prescription, frame, and lens design are otherwise comparable.
No. 1.74 can be thinner, but 1.67 may already provide enough thinness for many strong prescriptions. The better choice depends on your prescription, frame dimensions, measurements, comfort goals, and desired appearance.
Not necessarily. A higher index can reduce the amount of lens material required, but finished weight also depends on material density, prescription, lens geometry, and frame dimensions.
1.74 deserves stronger consideration when the prescription is high, the frame is relatively large, or reducing visible lens thickness is one of your highest priorities.
They can be. 1.67 is already a premium high-index material and may provide an excellent balance of thinness and practicality for many strong prescriptions.
Yes. Larger lens openings generally require more lens material and can make thickness more visible. Choosing an appropriate frame size can be as important as choosing a higher index.
Generally, yes. Minus lenses used for nearsighted prescriptions tend to be thinner through the center and thicker toward the edges.
Generally, yes. Plus lenses used for farsighted prescriptions tend to be thicker through the center, with the final thickness influenced by lens diameter, design, and prescription.
In many cases, yes. The frame must remain in suitable condition and be compatible with the prescription, lens material, frame dimensions, and mounting requirements.
KEEP YOUR FRAMES · UPGRADE YOUR LENSES
Choose the lens category you need, compare the available materials, and order new prescription lenses for compatible frames you already own.
