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Comment by arethuza | Hacker News Reader

We got a scare a couple of years back when our teenage son got an eye infection - the doctors and eye hospital went through five different antibiotics before finally finding something that fixed it, which was quite stressful.

NB When you are warned not to wear contact lenses in swimming pools - take it seriously! We're almost certain that's how he got the problem.

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That sounds really scary. I have gradually given up on contacts and gone back to glasses over the years - partly because of comfort, and partly because of hearing nasty stories of infections and complications caused by keeping them in too long.

If you wear contacts and follow all the rules exactly (like always taking them out before swimming/water sports, taking them out after X hours of wear each day, etc), I feel like they lose a lot of the convenience that made them so appealing in the first place.

You really want to just stick them in your eyes first thing in the morning and then forget about your crappy eyesight until bedtime, but it never seems to quite work out like that. (At least not for me, I have friends who wear them day in, day out with no apparent issues).

I've worn contacts for over 30 years (although I've only worn them for sports for the last 12 years or so) and I've never had any serious problems.

My son had them for a week and run into that problem and hasn't worn them since.

I've been wearing contacts most of my life and have never heard said warning. Given pools are typically fairly sterile, I'm not sure if understand it.

Now freshwater lakes or oceans under certain conditions I could understand

Swimming pools are far from sterile. The chlorine and other additives serve to inhibit the growth of organisms, but with so many contaminating bodies in it, they are far from sterile. Some public pools, not assiduously managed, at the end of the day, take on more than the aroma of chlorine; but even those that don't are not free of bacteria and other interesting life.

Well I specifically didn't say "sterile" but rather "fairly sterile" compared to other water sources.

Edit: As a note to the pedants, of course sterile" is a binary, I used that casually to mean "less microbrial than a lot of the places where our eyes go." ;) <- right eye unfortunately hit the unsterile waters of a chlorinated pool.

As a former boss used to say, there is no "fairly sterile" just as there is no "fairly pregnant".

> As a former boss used to say, there is no "fairly sterile" just as there is no "fairly pregnant".

This (and mrob's post) is definitely incorrect. It's the opposite, in fact, there is no "sterile" in the absolute sense. You'll never kill everything.

This is measured in multiple ways, depending on field: sterility assurance level[0] is one, similar to the way the USDA specifies cooking temperatures to hit 6- or 7-log reduction in bacteria populations. This is also why we crash probes like Cassini into Saturn to not risk contaminating any possible niches that could support life even though the probes have been built in a clean room, cleaned, and irradiated.

[0] https://en.wikipedia.org/wiki/Sterility_assurance_level

> This (and mrob's post) is definitely incorrect. It's the opposite, in fact, there is no "sterile" in the absolute sense. You'll never kill everything.

I suspect that there's some level of heat at which you've done exactly that. What organic molecule is going to survive a bath in liquid tungsten? ~6100F

"It's life Jim, but not as we know it" ;).

Sure, but usually the problem is the thing you're trying to sterilize won't survive either :)

There's also flaws in procedure -- was it at the required temperature long enough -- and, of course, the real world that your target is going to be exposed to when it leaves the tungsten bath -- clean rooms aren't all that clean.

There is no "fairly sterile" -- things are either sterile or they're not. "Sterile" means zero viable microbes. It might be fairly sanitary compared to other water sources but any water treatment that's actually sterile is going to kill the swimmers.

It seems like a lot of these warnings relate to reusable lenses. I use daily disposables, and I really can't see how, say, getting tap water on them when I'm wearing them can be any more dangerous than splashing tap water in my eye.

I don't think that's true at all. I think the issue with contacts (even dailies) is that they can trap pathogens on the surface of the eye and give them a place to breed, allowing an infection to take hold. This could happen within a day while you have your lenses on.

I think dailies are somewhat safer, because you're starting each day with a sterile pair. But splashing any non-sterile water onto them is a mistake.

I think that one source of infection is dirty storage pots. That's what NHS Choices says, and they tend to be evidence based (although we can argue about the evidence they use).

http://www.nhs.uk/Livewell/Eyehealth/Pages/Contactlenssafety...

That seems plausible. But I was once told that ideally you shouldn't even take a shower in contacts (Not that I always followed that advice). Maybe I just had an over-cautious optometrist.

It's definitely the standard advice, I just wonder how much evidence there is to support it. I guess it does make sense that the lens might make it easier for the bacteria to breed.

If any microorganism gets in your eye, it will usually be washed out of the eye by your tears and the sweep of the eyelid. If you're wearing contacts, it can get trapped in the film of liquid between the contact lens and the cornea, or in the film around the edge, and the tears and eyelid sweep will not be able to eliminate it. It's then in an environment where it's free to multiply and cause problems.

I don't think swimming pools are that sterile:

"“It doesn’t matter if it’s fresh water or a chlorinated pool,” Gibbons said. “There are bugs and pathogens that chlorine doesn’t kill, which could potentially cause damage to the cornea, infection or ulcers.”

http://healthcare.utah.edu/healthfeed/postings/2015/07/07141...

Perhaps some bugs are evolving resistance to chlorine?

I assume it's possible.

They can't really become resistant to high concentrations of cleaning products like chlorine bleach because they just physically ruin the organism - the best explanation I've heard is that that would be "like a human becoming resistant to lava." Not gonna happen.

But in really low concentrations like in a pool, perhaps they could resist the oxidation effects...

I thought the opposite: http://uk.businessinsider.com/terrifying-facts-about-public-...

Were these soft or hard lenses?

The one time I had to switch to softs, I had an infection in 2 weeks. My lens hygiene procedures are not compatible with softs apparently.

They were single use daily soft lenses - which I've used for a few years.

He had only been using them for a week or so and wasn't that good at getting them out so I suspect he must have scratched his eye while getting them out after swimming.

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