1.56 vs. 1.61 vs. 1.67 Lenses: Which Index Should You Choose?

Shopping for prescription glasses online comes with one question that is easy to overlook: should you choose 1.56, 1.61, or 1.67 index lenses? The numbers may look technical, but they describe how efficiently a lens material bends light—and help determine how thick your finished glasses may be.

The short answer: 1.56 is often a practical value option for lower prescriptions, 1.61 can offer a useful balance of thickness and cost, and 1.67 is worth considering for stronger prescriptions or larger frames. None is automatically best for every wearer.

What does lens index mean?

The refractive index measures how strongly a lens material bends light. A higher index can achieve the same prescription with less lens curvature and, in many designs, less thickness. The actual result depends on your prescription, lens design, frame size and shape, and how your pupils align with the frame.

1.56 vs. 1.61 vs. 1.67: a practical comparison

These are general comparisons, not fixed prescription cutoffs. A small, well-centered frame with 1.61 lenses can sometimes produce a better-looking result than a much larger frame fitted with 1.67 lenses.

Which index makes sense for your prescription?

Lower prescriptions: start with the frame

For a relatively mild prescription, the thickness difference between indexes may be modest. A comfortable frame that fits your face and places your pupils close to the lens centers often matters more than paying for the highest index.

Moderate prescriptions: consider 1.61

With a moderate prescription, 1.61 can be a sensible middle ground. It may reduce visible edge thickness in minus lenses or center thickness in plus lenses, although the exact savings vary by prescription and lens geometry.

Stronger prescriptions: evaluate 1.67

For higher prescriptions, particularly when thicker lens edges are a concern, 1.67 deserves consideration. However, higher index is not a promise of the lightest possible glasses: material density, frame weight, lens diameter, and minimum thickness requirements also affect the final weight.

If you have a stronger minus prescription, read our guide to choosing glasses for high myopia before selecting a frame.

Why frame size and shape can matter as much as lens index

A wide frame usually requires a larger lens blank. With minus prescriptions, this can increase edge thickness; with plus prescriptions, lens shape and required center thickness are especially important. Smaller, rounded or softly rectangular frames may help manage lens thickness, provided they fit properly and match your preferred style.

Frame fit also affects optical centration. Before ordering, check the frame measurements and follow our eyeglass frame size guide.

Does a higher index mean clearer vision?

Not necessarily. All three indexes can provide clear prescription correction when manufactured and fitted correctly. Lens design, accurate prescription measurements, appropriate coatings, and proper centration are often more important to everyday visual comfort than index alone. Some higher-index materials have different optical properties, including chromatic dispersion, so choosing the highest number without considering your needs is not always the right approach.

What about progressive, bifocal, photochromic, and sunglass lenses?

Lens index is only one part of a lens order. Whether a particular index is available with single-vision, progressive, lined bifocal, photochromic, polarized, or other lens options depends on the lens design and material offered for that combination. If you need multifocals, start with the lens design and fitting requirements, then choose a compatible material. Our bifocal versus progressive lens guide can help.

Three things to check before ordering prescription glasses online

1. Your full prescription: Include sphere (SPH), cylinder (CYL), axis where applicable, and ADD for multifocal prescriptions. Both sphere and cylinder can influence finished lens thickness.
2. Your pupillary distance (PD): Accurate centration matters. If you are unsure of your measurement, see how to measure your PD.
3. Your frame and total lens price: Compare the finished combination rather than the index alone. Consider fit, coatings, lens type, and any upgrade charges.

Frequently asked questions

Is 1.67 better than 1.61?

1.67 can produce a thinner lens for some prescriptions and frames, but it is not universally better. For a mild prescription, the difference may not justify an upgrade. For a stronger prescription, it may be worthwhile.

Is 1.56 suitable if I have astigmatism?

Possibly. Astigmatism by itself does not determine the best index. The complete prescription, including sphere, cylinder, and axis, plus frame dimensions, should guide the decision.

Are 1.67 lenses always lighter?

No. Higher-index lenses can be thinner, but final weight depends on material density, lens dimensions, and the frame. Thinner does not always mean lighter.

Should I choose a smaller frame for strong prescriptions?

Often a smaller, well-fitting frame helps control thickness, especially for stronger minus prescriptions. But the frame still needs to fit your face, pupil position, and visual needs.

Our recommendation: choose the complete pair, not just a number

For many shoppers, 1.56 is a reasonable starting point for mild prescriptions, 1.61 offers a useful middle option, and 1.67 can be worthwhile when thickness becomes more noticeable. The best choice is the one that fits your prescription, frame, visual needs, and budget together.

Explore EYEisland eyeglass frames, and if you are uncertain which index suits your prescription and chosen frame, contact the EYEisland team before placing your order.