High Index Lenses

Combining Transition Lenses and High Index Lenses: What You Need to Know

They are two technologies that have revolutionized modern eye-wear, and often lead the list of desirable options when selecting a pair of prescription eyeglasses: transition lenses and high index lenses. So can they be combined? The short answer is yes, with limitations. Let’s start by defining the two technologies.

High Index Lenses with Transition Lenses?

Transition (or photochromic) lenses automatically darken when exposed to the UV light of the sun and revert back to clear at night or indoors. They are essentially a combination of prescription eyeglasses and prescription sunglasses, and the use of transition lenses virtually eliminates the need to purchase, keep handy, and swap between regular glasses and sunglasses. While they do possess some drawbacks – not getting as dark as some sunglasses, for example, or not darkening inside the already UV-protected windshield of a car – the convenience of transition lenses makes them a popular item.

High index lenses are made of either glass or plastic, formulated from chemically-developed, high index materials as opposed to standard glass or plastic lenses. With high index lenses, stronger prescriptions can be cut using less overall material, reducing both the weight and thickness of the lens. This allows the wearer to choose from a variety of frame options that would otherwise be unfeasible with thick, heavy standard-glass or plastic lenses. Additionally, high index lenses minimize distortion, helping to prevent the “bug eye” or “tiny eye” appearance often associated with stronger prescriptions.

High index lenses are available in transition options, such as Transitions Signature Series and Transitions Xtractive, that change from light to dark, adapting to varying light conditions. These coatings are fully compatible with plastic high index lenses but cannot be applied to glass high index lenses. High index transition lenses are primarily available in single vision and progressive no-line bifocals, while options for lined bifocals are limited. The choice between high index glass or plastic is often dependent on the specific prescription; certain stronger prescriptions are only available in high index glass, which precludes them from having the photochromic coating.

The following high index ratings are made of plastic and can be ordered with a photochromic layer:

• 1.56
• 1.60
• 1.67
• 1.74

Higher ratings, such as those listed below, require the use of glass high index material and cannot be ordered with a photochromic layer:

• 1.80
• 1.90

To summarize, your ability to order a high index lenses coupled with a transition coating is limited by the strength of your prescription. Many prescriptions are mild enough to be cut from either standard glass/plastic or high index plastic and can be combined with a photochromic coating. Those prescriptions that require a high index material rating of 1.80 or above also require the use of glass high index material, thus are exempt from a transition coating.

October 11, 2024

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