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I'm a commuter cyclist. I have a pair of Persol sunglasses with leaded crystal lenses. Do y'all think this is dangerous in case of an accident? I have terrible thoughts of wrecking and glass shards going into my eyes, but I'd rather not carry two pairs of sunglasses. Thanks in advance for your answers.

Edit to respond to below comment because I can't comment yet: I don't know their behavior when impacted... that's kind of what I'm getting at with this question.

Richard

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  • Will they shatter or just break? It's probably just as bad to have broken plastic in your eye.
    – ebrohman
    May 2, 2016 at 22:20
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    I don't know about non-prescription stuff, but all prescription eyewear sold in the US must employ some form of "safety glass" to minimize risk of injury.
    – Daniel R Hicks
    May 3, 2016 at 2:03
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    The differences of safety in things designed to meet minimum safety standards can be significant. And I've never seen a shattered plastic lens for prescription eyewear.
    – Batman
    May 3, 2016 at 4:54
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    Best sunglasses for cycling have shatter-proof polycarbonate lenses. Don't just think of falling, think of stones thrown up by a passing cars. If it shatters a glass-lens the risk of injury is much greater.
    – Carel
    May 3, 2016 at 7:38
  • It's not just about the lenses. I once hat the frame of (very) cheap plastic sunglasses break upon impact, leaving a nasty scar a few millimeters away from my right eye. Well made glass-based sunglasses can potentially be safer than brittle giveaways.
    – linac
    May 3, 2016 at 9:48

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I have had my glasses damaged when falling off/getting hit on my bicycle, even with a helmet. Since my lenses are polycarbonate, they tend to just bounce on the road if they do come out of the frame. I'd think in some of those hits that my glasses would have broken if they were made from glass (especially when my glasses have hit the curb or rocks).

Based on this experience, I wouldn't risk using glass based sunglasses on a bicycle if I had the option. You can find safety glasses which act like sunglasses for a relatively low price, which don't look bad (e.g. the Uvex SafetyPro line) [but note these are likely not tested for sports, but are designed for some level of safety].

The best person to ask would likely be an optometrist or eyeglass retailer (the former likely being less biased than the latter) on what they would suggest for sports. This article (Cobb, Clark, and Chad Hulsopple. "Eye injuries in athletes." eMedRef (MU) (2010).) suggests use of polycarbonate for sports.

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    +1 for a science-based answer (and even a citation :-) While from my professional knowledge, lead crystal doesn't shatter as easily as "plain" glass, it does shatter. It doesn't require a direct impact on the front of the lens either. As you say, polycarbonate is the way to go.
    – andy256
    May 3, 2016 at 3:58
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As a blind mole cyclist who has worn glasses for 30+ years, I'm more scared of dropping my glasses and smashing them on the ground. Without my prescription glasses, I can walk but I certainly can't ride or drive safely.

However my helmet is always worn properly, so it provides a shelf of protection out from the forehead.

I've had two significant accidents/falls, and neither time have I had a problem with glasses. They didn't fall or break, just needed a clean afterwards.

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    The reason I went for (soft) contact lenses when I took up cycling more seriously! An you can wear them with proper cycling eye protection.
    – Carel
    May 5, 2016 at 7:59
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    Contact lenses can be quite different in comfort depending on the person. I hate wearing mine.
    – Batman
    May 29, 2017 at 22:22
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    My prescription glasses have been plastic for at least 30 years. Haven't yours?
    – David Richerby
    Jun 19, 2019 at 13:02
  • @DavidRicherby my current pairs are both plastic, but one's developed a crack through age/usage which is growing slowly. Plastic won't shatter like glass, but it will still break, and its more susceptible to scratching.
    – Criggie ♦
    Jun 19, 2019 at 20:00
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I personally don't think it is something to stress over. Most times glasses will break at the frame before the actual lens shatters. More than likely you will break a lens free of the frame rather than shattering it in the frame.

If there is an impact centered on the lens strong enough to shatter it, more than likely your eye would be harmed either way. Any non-direct impacts would probably be dispersed enough to simply twist the frame out of alignment popping the lens free.

Also, any direct impact to the glass lens would more than likely have equally horrendous outcome with a plastic type lens.

Generally when there is an accident, bike or no bike, your bodies natural tendencies to guard your face kicks in, you turn your face away from direct impact, put a hand or arm up, and flinch (closing your eyes). Which is why i think the chances of glasses shattering into your eyes is quite low.

However that's not to say it couldn't happen in a worst case scenario. Contacts for commuting would be one option, switching to the glasses if preferred once at work or wherever you're commuting to. I'd stick with glasses though if it were me.

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    I'm sorry to say Nate, but this answer seems to be mostly guesses.
    – andy256
    May 3, 2016 at 3:53
  • Well, when my sister accidentally head-butted me in the eye when I was a child, the glass lens of my glasses was smashed. I was lucky that no glass went in my eye, but I don't remember any damage beyond bruising from the impact. If the lenses had been plastic (and they were, after that!), the lens certainly wouldn't have shattered, and I don't see how the bruising would have been worse. So I dispute your claim that direct impacts are "equally horrendous" to glass and plastic lenses.
    – David Richerby
    May 29, 2017 at 20:34
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Personally, I wouldn't ride a bike with any glasses which have metallic frame (especially without flexible grips) and real glass lenses because of their weight and potentially sharp edges. I've seen a friend of mine who got pretty deep cuts on his nose after falling from a bike (wearing his expensive and heavy Police sunglasses which tore skin from his nose). (And after that injury he couldn't wear glasses for quite some time).

Since I needed both corrective lenses (myopia) and sun protection I've ordered custom tinted plastic polycarbonate lenses and semi-rimless frame with flexible grips and that costed significantly less than some brand name sunglasses.

I could recommend above mentioned type of glasses (with or without prescription :). These glasses are quite light, flexible and can come off easily in case of falling. (Didn't fall with my glasses on so far, but I've dropped them numerous times and sat on them once - luckily no big damage).

EDIT: I wanted to edit this question a long time ago because I've put the wrong term plastic were it should be polycarbonate.

As David Richerby mentions in his comment below, plastic is bad material for lenses due to fragmentation upon impact.

Here is a video which displays difference between plastic and polycarbonate lenses. Polycarbonate lenses won't shutter when impacted/stressed.

On the other hand, I would disagree about type of frames and whether semi-rimless or rimless frames are durable enough.

Another video of testing a sport performance product - a semi-rimless glasses from well known manfuacturer.

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  • This seems like bad advice. Metal frames can bend, whereas plastic frames are more likely to break in two. And many plastic frames have a metal core, anyway. (Semi-)rimless designs aren't as strong, so seem more likely to break. (Also, rimless frames aren't available for all prescriptions.)
    – David Richerby
    May 29, 2017 at 20:36
  • Also if pushed down onto your face, the lower edge of glass or plastic semi-rimless lenses is likely to be thinner and more square-edged than a frame and more likely to cut you.
    – Chris H
    May 30, 2017 at 6:37
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    As an anecdote, I was hit in the eye with squash ball while wearing semi-rimless metal framed prescription glasses with some kind of plastic lenses. The frame was bent and the lens slightly cracked in one corner, but I wasn't hurt at all. I have been using protective goggles for squash since then, but wouldn't call half-rimless glasses a hazard.
    – ojs
    May 30, 2017 at 19:19
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    Polycarbonate is a type of plastic. CR39 is a different type of plastic. It is incorrect to say polycarbonate instead of plastic.
    – Eric S
    Feb 25, 2018 at 3:07
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Persol's website mentions "crystal lenses" but leaded crystal is solely used in glassware, never eyeglasses. ie it does not exist. These look to be fashionware, and not protective at all.

Consider the ANSI testing and certification for safety lenses, which includes the behavior of frame materials as well. just Google "youtube ansi z87 testing" for a quick study, which more than answers the original query.

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When the first words used are "I personally don't think" I would tend to take the subsequent advice with extreme caution. There are well-established criteria for safety glasses that opinions do not circumvent, which many brands like Oakley meet or exceed in their entire lines of sports eyewear; they also have separate lines for ballistic protection, which meets much higher impact velocity standards for military/shooting protection. ANSI Z87.1 should be the minimum for safety, as both shatter resistance and impact penetration from things like rocks kicked by passing cars can go right through the wrong plastics, and no type of glass is safe. Falling can also shatter bad eyewear, and long shards of glass or plastic can blind you - an extremely poor tradeoff in cost and fashion vanity. Those tests on YouTube are the real deal, and you can't judge just by looking at a pair whether they will protect or not. As an aside, I'm doubting the worth of this stackexchange experiment, as too much of the advice seems to come not from those with insider knowledge, but from people just spouting opinions free from even personal anecdotal experience half the time. Honestly, when it comes to technical advice, some opinions are worth a lot more than others, and having to read through the uninformed when life or health is at stake, and try to differentiate good from bad makes for a very inefficient forum paradigm.

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    Please stick to the question. If you want to take issue with the way that people use the site (it's not a forum, by the way), please use Bicycles Meta.
    – David Richerby
    May 29, 2017 at 20:37
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    Youtube videos might be good supporting information but in no way are proof. Certifications are the real deal.
    – Criggie ♦
    May 30, 2017 at 2:23

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