Understanding Lens Index: A Comprehensive Guide To Eyeglass Lenses

There is a common misconception that the stronger your eyeglass prescription is, the thicker the lens, but choosing high-index lenses keeps your lenses slim and thin since they bend light more efficiently to correct your vision.

Index lenses can be categorized by different gradients which we will explore in our guide, typically, the higher the index then the stronger the prescription for nearsightedness, farsightedness, and astigmatism.

Below, we’ll discuss how to determine your lens index and where to shop for high-index lenses.

What Is Lens Index?

Lens index is measured by the refractive index which refers to how efficiently a lens can bend light and is measured in numbers.

Stronger prescriptions need a higher refractive index number, this changes according to how quickly light travels through the material.

Higher index glasses have ultra slim high refractive lenses to provide style and comfort while accommodating a stronger prescription.

The most common lens indexes are; 1.50, 1.57, 1.59, 1.61, 1.67, and 1.74.

The higher the index number, the thinner the lens. You can read more about glasses lenses here.

Types Of Lens Index

Index lenses have different gradients and are matched according to your prescription.

• Standard 1.50 index lens - These are standard single-vision lenses made from basic plastic and are best for people with a weak prescription. They are also very affordable.

• Balanced 1.57 index lens - These offer a balance between thickness and weight and are best for individuals with moderate prescriptions.

• Polycarbonate 1.59 index lens - Made from a unique polycarbonate material they are tailored to each individual. Anti-reflective and scratch-resistant coatings can be applied to these lenses for durability.

• High 1.61 index lens - These lenses are very thin and light and are best for people with moderate prescriptions who want lightweight lenses.

• Middle ground 1.67 index lens - Best for people with moderate to high prescriptions.

• Thinnest 1.74 index lens - These are the thinnest lenses designed for the highest prescriptions. They are best for rimless metal frames or semi-rimless styles where you need your lenses to look minimal. They are 45% thinner than standard lenses.

You can look at a lens index chart to see all the different strengths.

How To Determine Your Lens Index

You can work out your lens index based on your prescription.

Prescription Strength

• Mild prescriptions - A prescription between 1.00 to 2.00 is a weak prescription and will usually only need 1.50 index lenses. These provide enough correction without being too thick.

• Moderate prescriptions - For prescriptions between 2.00 to 4.00 consider choosing 1.57 and 1.59 index lenses. These give a good balance of thickness and weight without ruining the aesthetics of your lenses.

• Strong prescriptions - If your prescription is stronger than 4.00 you will need to opt for high-index lenses such as 1.61, 1.67, and 1.74. These lenses are very thin and light, making them comfortable to wear and reducing the Coke bottle effect that often occurs with thicker lenses.

You can read more about how to read your prescription here.

Frame Style

• Frame type - Rimless or semi-rimless frames benefit from higher index thin lenses such as 1.67 or 1.74 to keep a sleek appearance. For people with a higher prescription check out our stylish high prescription glasses here.

• Frame size - Larger frames often need thicker lenses for support and are more common if you have a higher prescription. Smaller frames accommodate thinner lenses better.

• Aesthetic preference - For a minimalist or fashionable look, thinner lenses at 1.61 or above can help achieve this. Thicker lenses appear bulky and less appealing.

Budget Considerations

• Cost of lenses - Standard 1.50 lenses tend to be the most affordable kind of lenses, when you move up to mid and high-index lenses the price will go up.

• Long-term value - High-index lenses cost more than low-index lenses but are of higher value thanks to their thin size and lightweight. This makes them more comfortable to wear with fewer adjustments needed.

If you are not sure about your current eye prescription we recommend consulting your optician to have a complete eye exam.

Find High Index Lenses At GlassesShop

GlassesShop has a large range of high-quality prescription eyeglasses and sunglasses to meet your vision needs, as well as high-prescription glasses for people who still want style despite needing a stronger prescription.

We have reading, progressive, and single-vision glasses as well as various lens coatings and index lenses. We have low-index lenses ranging from 1.57 and 1.59 Polycarbonate high impact to 1.61, 1.67, and 1.74 which can all come with anti-scratch, anti-reflective, and UV coatings.

If you're not sure about the style of glasses that suits you, use our free home try-on service, allowing you to order up to five pairs of glasses to try on at home.

Our glasses are also affordable with deals such as buy one get one free, flash sales, and 50% off new arrivals. We also have free shipping over $69 and a 365-day guarantee.

You can check out more about our lenses here.