Customize Your 1.67 or 1.74 High Index Lenses into Sunglasses
High index lenses are thin, lightweight, and compatible with a variety of attractive and stylish frames. That’s all well and good but what about outdoor use? Are there high index sunglasses? Two possible options are wearing a pair of flat sunglasses over the prescription glasses, or using clip-ons. Apart from the clunkiness and less than stylish appearance of wearing two pairs of glasses, there’s the problem of carrying around the sunglasses. It’s an extra complication, which means that sometimes you won’t have them when needed, you can lose them, and all the handling increases the risk of scratching or damaging them.
On the other hand, clip-ons are easier to carry around, and look better. But again, it’s one more thing you’ll have to carry around, which introduces the same inconveniences of using a pair of flat sunglasses. Another problem is their repeated clipping and removal makes it likely they’ll eventually break. However, you can customize your 1.67 or 1.74 high index eye-wear into sunglasses by choosing the right options. In addition, it isn’t necessary to customize a separate pair of glasses just for outdoor use. This will be explained later.
The Requirements for Sunglasses
Sunglasses should do three things. They should reduce sunlight intensity, glare, and block out all UV light. All of these are important. Intense sunlight causes squinting, which is uncomfortable and causes eyestrain, fatigue, and possibly headaches. Glare causes the same problems, and also interferes with clear vision. Our eyes can’t process the extreme contrast produced by glare from reflections off shiny objects or from the sun when it’s low in the sky.
Blocking out UV has nothing to do with comfort because you can’t see or feel it, although you will feel its aftereffects in the case of sun blindness. However, this requires extreme UV exposure. For moderate exposure levels, the problem is cumulative eye damage that may cause serious vision problems later in life. Fortunately, most high-index plastics naturally block out all UV light. However, you should always verify this before your purchase.
A functional pair of sunglasses limit your frame choice somewhat. Namely, you can’t use a frame style that accommodates very small lenses. If you like glasses with small lenses, there is little point trying to customize them into functional sunglasses. The reason is too much UV light will reach your eyes from bypassing the lenses entirely. Select a frame that accommodates the largest high index lens possible. The frame should also fit closely. These two requirements will prevent UV light from “leaking in” through the sides.
Sunlight Intensity and Glare
Although polarized lenses do a good job of eliminating glare, they aren’t versatile. They can distort your view of some digital displays and they cut down light intensity. Less light transmission makes them less useful indoors and dangerous at night. They are meant for use in outdoor daylight.
Unless you intend to have two separate high index glasses for indoor/night and outdoor/day use, applying a transition tint on a single pair of glasses is a better option. Transition tints respond to bright sunlight by darkening into sunglasses, but become clear when you’re indoors and at night.
Transition tints can take a few minutes to adjust either way, and are activated by UV light. If your car’s windshield blocks UV, then the tint won’t darken. However, an inexpensive clip-on kept in the glove compartment is a good work-around for this problem. Transition gray and transition brown tints are available for 1.67 and 1.74 high index lenses. Gray tint allows true color perception, while brown increases contrast. Transition tints also block out all UV light.
By avoiding small lens sizes and adding a transition tint to your high index lenses, you will effectively have a pair of eyeglasses that turn into sunglasses outdoors but remain useful indoors and at night. The transition tint eliminates the light intensity, glare, and UV problems. The largish lens size and the high index lens material, also block UV.