2024-11-15
Not All Sunglasses Protect Your Eyes
You can buy sunglasses for $10 at a gas station or $400 at an optical shop. They might look identical from the outside. But the difference in what they do to your eyes can be significant, and the labels on the hang tag do not make it easy to figure out which is which.
UV protection is not a luxury feature. It is the entire point of sunglasses from a health perspective. Cumulative UV exposure contributes to cataracts, macular degeneration, pterygium (that fleshy growth surfers get on their eyes), and even cancer of the eyelid skin. This is not theoretical. It is well-established medical science.
So let us decode what the labels mean and what actually matters.
UV400 vs "100% UV Protection"
These two labels mean the same thing. UV radiation is divided into UVA (315-400nm) and UVB (280-315nm). "UV400" means the lens blocks all wavelengths up to 400 nanometres, which covers both UVA and UVB completely. "100% UV protection" or "100% UVA/UVB" is the same claim in different words.
This is the minimum you should accept in any sunglasses. If a pair does not have one of these labels, do not buy them. A dark lens without UV protection is actually worse than no sunglasses at all. Here is why: the dark tint makes your pupils dilate (open wider), which lets in more light. If that light is unfiltered UV, you are exposing your retina to more UV than you would with bare eyes. Your natural squint reflex protects you more than a dark lens with no UV filter.
Polarized: Real Benefit, Not UV Related
Polarized lenses block reflected glare. When light bounces off a flat surface like water, snow, wet pavement, or a car hood, it becomes horizontally polarized (the light waves align in one direction). Polarized lenses have a vertical filter that blocks this specific type of glare.
The practical effect is dramatic. If you have ever worn polarized sunglasses while driving on a wet highway or fishing on a lake, you know the difference. Reflected glare essentially disappears.
But polarization has nothing to do with UV protection. A polarized lens without UV coating still lets UV through. And a non-polarized lens with UV400 blocks all the UV just fine. Polarization is about visual comfort and glare reduction, not eye health. They are separate features.
That said, any quality polarized sunglasses will also have UV400 protection built in. It is the cheap polarized glasses where you need to check.
Lens Categories (1 through 4)
You might see a category number on some sunglasses, especially European or Australian brands. This refers to how dark the lens is:
- Category 0: Clear or very light tint. Fashion glasses, not sunglasses. 80-100% light transmission.
- Category 1: Light tint. Good for overcast days. 43-80% light transmission.
- Category 2: Medium tint. Good for moderate sun. 18-43% light transmission.
- Category 3: Dark tint. What most sunglasses are. Good for bright sun. 8-18% light transmission. This is what you want for general outdoor use in Alberta.
- Category 4: Very dark. For extreme conditions like glaciers or high altitude. 3-8% light transmission. Too dark for driving (illegal to drive with in most jurisdictions, including Alberta).
The category tells you about visible light transmission (how dark the lens is), not UV protection. A Category 1 lens can still have UV400 protection. Darkness and UV filtering are separate characteristics.
Lens Colour: Does It Matter?
Tint colour is mostly about contrast and comfort in different conditions, not about protection:
- Grey: Neutral colour perception. Everything looks natural, just dimmer. Best all-around choice.
- Brown/amber: Enhances contrast slightly. Good for driving and variable conditions. Many people find brown tints more comfortable than grey.
- Green: Similar to grey but with slightly enhanced contrast. Classic Ray-Ban G-15 is a green tint.
- Yellow/orange: High contrast. Good for overcast or low-light conditions but too bright for full sun. These are not sunglasses colours; they are sport-specific tints for shooting, skiing in flat light, etc.
- Rose/pink: Enhances depth perception and contrast against green and blue backgrounds. Niche use.
For general UV protection, the colour of the tint does not matter. What matters is the UV filter built into or coated onto the lens material. Choose your tint colour based on what looks good and feels comfortable, not based on protection claims.
Alberta-Specific Considerations
We live at a latitude and altitude where UV exposure is significant. Alberta gets intense sun in summer, and snow reflection in winter doubles your UV exposure from below. If you ski, snowboard, or spend time on frozen lakes in winter, UV protection is just as important in January as it is in July.
Wraparound sunglasses or styles with good coverage around the sides block UV from entering at the edges. This matters more here than in less sunny climates. A narrow aviator looks great but lets a lot of peripheral UV in.
Prescription Sunglasses vs Clip-Ons vs Photochromic
- Prescription sunglasses: The best optical quality and most comfortable option. The main downside is cost and needing to carry two pairs. Worth it if you spend significant time outdoors.
- Clip-ons/fit-overs: Functional, affordable, slightly awkward looking. Magnetic clip-ons designed for your specific frame are much better than generic ones. A good option if prescription sunglasses are not in the budget.
- Photochromic (Transitions): Lenses that darken in sunlight and clear indoors. Convenient since you carry one pair. The downsides: they do not darken inside a car (the windshield blocks UV that triggers the darkening), they take a few minutes to fully clear when you come indoors, and they do not get as dark as dedicated sunglasses. In cold weather they get darker and take longer to clear. In hot weather they do not get as dark.
The Simple Buying Guide
When buying sunglasses, check for three things:
- UV400 or "100% UV protection" on the label. Non-negotiable.
- Adequate coverage. Bigger is better for actual protection. Side coverage matters.
- Polarized if you drive, fish, ski, or spend time around water and snow. Optional but worth it for comfort.
Everything else, the brand, the colour, the category, the price, is either personal preference or specific to your use case. A $20 pair from a pharmacy with UV400 protection protects your eyes exactly as well as a $300 designer pair, assuming the UV claim is accurate. The expensive pair might have better optics, better frames, and better coatings, but the UV protection is identical.
If you want to be certain about the UV protection on a pair of sunglasses, any optical shop can measure the UV transmission with a lensometer in about 10 seconds. Bring in your favourite gas station sunglasses and we will tell you exactly what they block. No charge, no sales pitch.