You might have considered transitions lenses as a solution to your need for corrective eyewear, UV protection, and discomfort from brightness in direct sunlight or nighttime driving. Transitions lenses are known for their gradual tinting, and adaptation to changing light conditions.
But it can be a severe challenge to optometrists striving to balance comfort, protection, and function in both eyeglass and contact lenses — and although transitions lenses are loved by some, they can’t please everyone. Sunlight and the spread of smart screens provide challenges to that balance.
Sunlight
Sunlight is great, but it’s not without its risks. Interestingly, most of the risks come from solar radiation that’s shorter in wavelength. From shorter-wavelength blue light to extremely short wavelength x-rays, our eyes can suffer under sunlight.
Fortunately, the atmosphere, especially the ozone layer of the atmosphere, protects life on earth from the shortest wavelengths. These types are Ultraviolet type C and X rays — the most typical parts of sunlight’s electromagnetic spectrum that doesn’t reach the surface.
However, not all UV light halts at the ozone layer. Ultraviolet types A and B still penetrate through to the surface. Moreover, sunlight is rich in blue wavelength light within the visible spectrum.
Ultraviolet Light
The outdoor hazard is the UV index. UVA and UVB sunlight penetrate the atmosphere. These rays (almost irreversibly) damage cells in both the eyes and the skin and UVA/B content in sunlight has been linked to the development of cataracts.
Blue Light
Blue light is the least harmful because it’s the longest wavelength. But our bodies are attuned to blue light for waking up, so blue light common to smart device screens can interfere with your body’s circadian rhythm. The sun is the primary source of blue light. Still, computer screens have also contributed to the average person’s exposure.
It’s also a risk factor for the onset of age-related macular degeneration, a type of vision loss that can be very hard to treat, regardless of the corrective lenses available.
Moreover, the International Organization for Standards has standards for the potential hazard, specifically ISO-8980-3 for 380-460nm (Blue Light Hazard Function B(lambda). If there’s a potential for hazard, it might be wise to look at protective equipment designed for it.
At this time, blue light shows no sign of being an overtly dangerous type of radiation. But again it’s not recommended to indulge in blue light too much, especially for children.
At the end of the day, it might be best to limit exposure to high sources of blue to violet light, however possible.
Brightness of Sunlight
There’s a shock of brightness when you walk out into late morning or afternoon sun. It can often lead to excessive squinting, which is a strain on your eye muscles.
The brightness of direct sunlight tends to be quite intense. It’s over 100 times brighter than indoor lighting or the average headlight on the highway.
It’s this discomfort that spurs most people to look for solutions, from traditional non-prescription sunglasses to the innovative “transitions” corrective lenses.
How Transitions Lenses Work
The key feature of transitions lenses is the activation of patented photochromic molecules, i.e. molecules that change colour according to how much light they receive. These molecules change structure when hit by light, leading to sunglass-like tint in the lenses. They return to a clear tint under normal lighting conditions.
There are two methods for joining the photochromic molecules to the corrective lens. The first is called imbibing. Imbibing comes from a Latin word meaning “to drink.” It involves embedding the photochromatic additives into the lens material through a heated process.
But some lens materials are more receptive to photochromatic imbibing than others. Another method simply coats the lens with an outer photochromic layer.
Transitions Eyeglass Lenses
These corrective lenses, available as a lens option for eyeglasses, have been around for decades. Their brilliance comes with some drawbacks, however.
Pros
- They’re conveniently usable as sunglasses outdoors or in mixed outdoor and indoor light.
- UV protection is constant.
- Inside or in low light, they’re entirely transparent.
- They can be used in any prescription style and shape.
- They can be combined with other lens coatings.
- They save you from buying a pair of prescription sunglasses.
Cons
- Some people might find the in-between stages of darkening a bit off-putting.
- Cold weather slows the transitions process.
- UV light is a key trigger for the process, so they might not darken enough inside a car (which has UV protection built-in).
Transitions Contact Lenses
These lenses have only been FDA approved recently, as there were more health and safety hurdles to pass for photochromic contact lenses. They have since been declared safe for prescription. They’ve been lauded by Time as one of the best inventions of 2018.
Pros
In some encouraging trials, transitions helped relieve eye stress for most, especially in outdoor daylight activities, indoor screen time, and night driving.
These lenses:
- Reduce opposing traffic’s halos by up to 18%, and starbursts by up to 28%
- Block up to 15% of indoor blue light, and up to 55% of outdoor blue light
- Block 100% of UVB, and over 99% of UVA radiation, especially beneficial for ages 40-65
- Provide 38% better colour contrast than ACUVUE® OASYS with HYDRACLEAR® PLUS
- Were preferred for their reduced eye stress due to brightness by 3 out of 4 surveyed
Notably, wearing these contact lenses allows you the experience of a seamless transition between lighting extremes, much like eyeglass transitions lenses.
Cons
- Transitions contact lenses come with the usual disadvantages of contact lenses, from mild irritation or discomfort to corneal ulcers.
- They require the same care and precautions as regular contact lenses.
- These contacts are safe only for 14 day periods, so they need to be replaced twice a month.
- Transitions contact lenses don’t replace sunglasses, because the contacts don’t cover and protect your entire eye.
- Because transitions contact lenses are not substitutes for 100% UVA/B screening sunglasses, you still need them.
- Because they’re so new, clinic trials to determine whether they increase the risk for eye disorders have not yet been conducted.
Best Uses for Transitions Lenses
You can always go with the tried, tested, and true eyeglass transitions lenses. Eyeglass’ lenses can be chosen with other features in mind, not just photochromic properties. They cover enough of your eye to protect your macula from exposure to UV rays. The detail-oriented part of your retina is mostly protected with transitions eyeglass lenses.
But these corrective transition eyeglass lenses can’t ever be shaped to wrap around the eye; corrective lenses need to be just concave (or convex) enough to refract light precisely. That’s why frames don’t come in a wraparound shape.
The Canadian Optometry Association recommends the wraparound style of sunglasses (with 100% UVA/B protection) for children. This advice comes based on the World Health Organization’s estimate that up to 80% of the damage from UV light occurs in childhood.
With transitions contact lenses, you can better leverage non-prescription wraparound sunglasses (even as an adult) for prolonged sunlit activity. The wraparound style will cover parts of your eyes that transitions eyeglasses just can’t.
After dusk, you can take off your wraparound sunglasses. The transitions lenses should improve your vision for activities like night driving.
You’ll be able to rely on the seamless transitions of the photochromic contact lenses between changing outdoor and indoor lighting conditions. That combination gives you more flexibility in shooting for full protection from UV light during the time spent outdoors.
Ask Your Optometrist
An adult conscious of the dangers of UV radiation can avoid the average remaining 20% of lifetime UV damage through proper eye protection while enjoying the comfort of transitions lenses. Doing so can now involve the seamless brightness comfort of photochromic lenses, whether eyeglass lenses or contact lenses.
