High Index Lenses

High Index Transition Lenses vs. Photochromic Lenses

Gone are the days when the only option for high-prescription eyeglass wearers was to look like you strapped a pair of magnifying glasses to your face.

Photochromic Lenses vs. High Index Transition Lenses

High index lenses offer the potential for lighter and certainly thinner eyeglass lenses than standard eye-wear materials, effectively eradicating the stigma of thickly framed, visually distortive “Coke Bottle” eyeglasses. Available in plastic or glass in a variety of indexes, high index lenses are also compatible with a number of protective coatings and treatments.

One option they’re not always compatible with is the transition, or photochromic, coating. Certain high index materials are available with the coating, but the nature of high index lenses often precludes the availability of transitional lenses. Not all manufacturers combine the two formats – especially on the higher-end high index materials like 1.80 or 1.90 glass lenses. If you want transition high index lenses you’re more likely to find them at the lower end of the index spectrum. 1.67 index lenses, for instance, are often available with photochromic lenses.

While on the subject, a bit of clarification on terminology is probably in order. “Transition” and “Photochromic” are interchangeable terms. They both mean the same thing and describe the same process: lenses that automatically darken in the presence of ultraviolet light and revert back to a clear state indoors or at night. “Photochromics” is the technical term for the technology used to accomplish this feat, but “Transition” is just as often used to describe such lenses. “Transition” derives not only from the descriptive action of the lenses but also from the company that first developed and marketed the photochromic coating, Transitions® brand lenses.

Since your preference for a certain high index material may force you to choose between it and photochromic lenses, here’s a snapshot of photochromic lens facts to help you decide:

• They react only to ultraviolet light, so do not darken when exposed to most forms of indoor, artificial lighting.
• Regardless of their state – fully clear, fully darkened, or anywhere in between – photochromic lenses provide 100% protection from both UVA and UVB rays.
• Many current automobile windshields are designed to block ultraviolet light. Therefore, photochromics typically do not darken fully when worn inside a vehicle. You may choose to wear a different pair of sunglasses or to supplement your corrective eye-wear with clip-on shades while driving.
• Transition lenses are fully compatible with most other coatings, such as anti-reflective, anti-fog, and scratch resistance.
• They’re available in a wide range of prescriptions and in a variety of specialty applications, such as bifocals and progressive lenses.