General Night Vision Question

[nostos156]

(Cross posted from a PM as I wasn't aware that was against rules)

I've been browsing this site for a few hours now and saw many helpful posts from you, so I figured I could perhaps ask a general question that has been bugging me for a while now, but hard to describe.

For reference, I'm a recently turned 23-year-old male who has been anxious about my eyes for most of this year, as I only recently found out in February that it turns out I don't see as well as I always thought I did (ended up with -0.5 and -0.75, with 0.25 astigmatism in one eye). Of course, I went into a panic thinking perhaps this was a recent development and my eyes were getting worse. Research into myopia seemed to dispell that, though, and it is probably likely that I had this all my life (the tell-tale sign was noticing that slight streetlight starbursting in the distance at night was eliminated with glasses. I remember always having that and just thinking it was normal for lights to do that [and wow, there's a lot of detail to stuff in the distance I didn't know existed]). That, and the fact that as myopia is governed by your eye shape, it seems really weird that it would suddenly change for the worse now, right? That being said, I really hate glasses and just opt to go without, still, and I have no idea if PRK surgery would be suitable for such a minor correction.

Of course, because I was freaking out about my vision at that point, I also began noticing floaters, which an eye exam did confirm that they could see a few of them. Even typing this, I have an annoying grey little one whizzing by every so often. Those are the worst as they instantly show up as blurry specks in bright backgrounds, whereas the stringy like one I have is practically invisible unless I go looking for it. It will probably take a long time for me to ignore those ones considering my profession will have my staring into a screen for a majority of my life.

However, moving on to the actual question, I read about 'visual snow' and wondered if seeing something akin to that, but only in the dark was normal? It is hard to describe, as it isn't exactly obvious like camera ISO snow in the dark. It's similar to when you shut your eye and palm it, and your brain starts conjuring up all these wonderful colours and little snow like effects. That's basically what I'm seeing. Is that a normal side effect of the pupil dilating in the dark in order to receive more light? Is your brain trying to fill in the totally dark sections, resulting in that effect?

As you can probably tell from my blathering, I'm noticing every tiny little thing now and having it bother me. My days of thinking I was invincible coming to an end and realising I'm like everyone else is hitting me hard currently.

Any insight would be greatly appreciated.

Regards,
Lewis

[JohnHaganMD]

Well good you have done some research but some things need to be clarified.  A eye with simple myopia (arbitrary but let's say less than 3 diopters of myopia) and no other problems is a healthy eye its just out of focus. Think about "old time" cameras that had to be manually focused. If it was out of focus the picture was blurry but the camera was good. It just needed to be turned to put in focus then the picture was clear.  So a healthy myopic eye might have 20/200 vision at distance without glasses and 20/20 with glasses but be healthy and an eye that sees 20/20 without glasses may be in extremely poor health (could have glaucoma, diabetic retinopathy or other serious diseases).  You have minimal myopia.  You don't mention your vision without glasses but apparently you've done well without glasses for a long time and still do.  If you function well without glasses you are not a good candidate for lasik, prk or any refractive procedure. You probably think you'll never be 40 but after 40 myopia helps your near vision. If you have lasik after 40 your near and intermediate vision will fail and you will be in progressive bifocals.  My refractive error is -2.50 and I love it as I can read without glasses and am using the computer without glasses.  When you close your eye and press on the eye (DON"T DO THAT)  its not your brain that creates the image its the retina responding to the pressure. It's an entopic phenomena.  I have said many times I know nothing from personal experience about visual snow. There is an extensive explanation in Wikipedia. People complain of it here but it's not something any patient of mine has ever described. Many patients however do not entopic phenoma like the "flying corpusule" blue field effect.  I have a huge Weiss ring in my right eye and I never thought I would get use to it but after several years I have "neuroadapted" it an all my other floaters out of my vision.  If your eye exams have all been normal perhaps get on with your life and confirm you do well without glasses and if you know it your vision without glasses. On your posting I don't think you are a good candidate for refractive surgery.

[nostos156]

Hi John,

Thanks for the response.

Yeah, I've gone through all 23 years without glasses and never actually noticed the slight blur in the extreme distance (and the slight double vision of LEDs and starbursting at night) was because of a refractive error until I was told it was. My worst eye I believe is 20/30, which means in the UK at least I'm still legally able to drive, so it's more of a mild inconvenience than anything. (What you don't know can't hurt you and all)

Well, I sure hope to not be needing glasses as well at 40, but since my myopia is so minimal that is probably a vain hope at best, huh? Sounds like it would probably progress into needing reading glasses eventually. Kinda makes me wish I had a slightly higher refractive error now as well! (Since I spend a good majority of my life reading small text on a screen). Is there any standardised data of myopia strength correlation to presbyopia and how it will affect the outcome of needing reading glasses, or is it one of the things I'll just have to find out when I come of age?

Not to worry, I don't palm my eyes ever, except once. I've googled visual snow but I'm not sure it is the same thing. I can see shapes in total darkness (when eyes have adjusted) but no discernable colour, it just looks like very faint noise, but it is so mild I can't even confirm if it is actually noise. I was just wondering if that kind of thing in total darkness was normal or not. This only happens during the dark, never during the day. I thought it was maybe just a entoptic phenomena, like your eyes see it for the same reason a camera does in the dark - with very little light to go on, your cones are at maximum possible sensitivity, but there's still not enough information for them to put anything together, so it just looks a little bit like random noise.

Thanks for the extensive reply.

[JohnHaganMD]

If a person is -1.00 myopic the myopia provides +1.00 diopters of reading power, if -2.50 then +2.50 reading add.  This is a very rough guide of how a person with no refractive error 0.00 would need in reading glasses at what age to correct presbyopia: 40 years old -start with a +1.00; 45 years old +1.50 50 years old +2.00 60 years old +2.50 - +3.00 So a person with a -1.00 refractive error might expect to be comfortable reading without glasses till about age 45-50.  However if the reading glasses he/she needs will be one diopter less because the myopia still contributes focus power. This at age 60 a person not needing glasses for distance would use a +2.50 reading glass but the one diopter myope would use a +1.50.

[nostos156]

Well, scratch what I said before. If this chart is correct:

https://www.welchallyn.com/content/dam/welchallyn/documents/upload-docs/Research/Reference/Spot-VS100-Screener-Visual-Acuity-Chart-Info.pdf

Then my left eye is 20/30-40 and my right eye is 20/50. But I was never told I'd need glasses to drive 'unless I wanted them' so nothing illegal there.

[nostos156]

Hrm,

Have you experienced people intentionally making their eyes more myopic through surgery in order to keep reading before? Of course, we're talking 30+ years away so who knows what options I'll have then.

[JohnHaganMD]

It is difficult to make an eye more myopic which requires the cornea to be made steeper or more curved. Lasik and PRK (and before that RK) work by making the cornea flatter. That is why farsighted lasik is not very successful.  There are quite a few procedures that are being tested to try and correct for presbyopia with something short of clears lens exchange for a multifocal IOL which is way too risky and costly.  Stimulation of the ciliary body is being tried. Corneal inserts which I think a very bad idea.  Given all the problems the body is subject to having one that is cured with reading glasses or progressive bifocals isn't all that bad.

[nostos156]

Hi John,

Back again as I read about Ortho-k, which would in theory, seem ideal for my extremely mild myopia. Pop in a lens overnight, and be able to see much better in the distance without any other correction for multiple days (apparently, the lower your correct, the longer you can go without).

However, there must be risks, right? I'm aware of the possibilities of infection from misuse and lack of attention to care, but how about unintended side effects?

I read that floaters may be caused by pressure on the eye. Isn't this exactly how Ortho-k works? If I could potentially cause more floaters, then I'd rather not.

[JohnHaganMD]

I have no personal experience with ortho-K other than several patients done elsewhere who were disappointed with it.  There has been some recent research that indicates it may have a role in developing myopia in reducing the total amount of final myopia. But there is no general agreement. Yes the risks include infection and damage to vision possibly permanent.

[nostos156]

Well, I contacted a local opticians who does them. Turns out the manufacturers will only supply them in the ranges -1.0 to -4.0, so I'm not eligible for that either.

I wouldn't have problems with soft contacts if they weren't so expensive, and then the astigmatism ones are even more pricey, and I didn't see them available under 0.50 astigmatism.

[JohnHaganMD]

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[SoftwareDeveloper]

re: ortho-k,  I'd suggest talking to an eye doctor rather than just  an optician if you were serious about it (though I think regular contacts are likely a better bet).  

I suspect that at your age they could likely over-correct your vision if they don't have an ortho-k lens that corrects less than 1 diopter of myopia. If your eyes are overcorrected slightly to be very slightly farsighted, hyperopic, then your eye would merely accommodate to focus well.  I haven't confirmed this (I was always highly myopic), but I think at your age that being very slightly farsighted wouldn't be a strain.  Ultra-near vision (like a few centi-meters from your eye) that is likely not used often wouldn't be quite as clear, but unless you need to do fine work that close up its likely you wouldn't notice.  


If you can drive without glasses, many people wouldn't bother with correction. However if you want the crispest vision possible, many people find soft disposable   contact lenses very comfortable and convenient if they don't like glasses. Some people have a little difficulty the first time they put something in their eyes, but most adapt quickly (and you'd need to do the same with ortho-k). Although ortho-k is worn while you sleep so you won't notice it except when trying to sleep, the lenses likely aren't going to be as comfortable as disposable soft lenses.  

[nostos156]

Considering how expensive they are, and how apparently I don't need the special astigmatism contacts for such a low value, it seems I'd get away with just buying regular contacts for whenever I needed to be outside all day.

At that point, Ortho-K probably doesn't seem worth it since it is always temporary anyway. I imagine contacts which correct under 1 dioper are probably extremely thin and more comfortable compared to the higher correction ones too?

[JohnHaganMD]

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[nostos156]

Back again for another round of curious question.

As for the Ortho-K, I did speak (over email) to an eye doctor. He said that regular contacts would be just fine, as with astigmatism under 0.50, the regular contacts would correct it anyway and mask it. I'm presuming this is true and I don't need to pay extra for the special ones?

Another question I had is, the main room I do my work in is a bedroom, with dark wallpaper. Ergo, I need quite a lot of lux in the room otherwise it is always too dark. Is there a generally accepted point where being too bright (measured perhaps in lux?) can damage your eyes?

Right now I have 3 1000 lumen LED bulbs under a rice paper shade to diffuse the light, and it works perfectly, everything seems nicely illuminated. However, will that kind of brightness cause any long term problems to my eyes, especially on those occasions I happen to glance at it?

[JohnHaganMD]

Ortho-K and regular contacts are two entirely different things. Ortho K worn at night to try reduce dependence on glasses during the day while regular contacts worn during day to obviate the need to wear glasses during day.   Half a diopter of astigmatism generally does not require a toric contact. Light bulbs you buy at the store are not going to damage your eyes. Some may be so bright they're uncomfortable.

[nostos156]

Hi John,

Yeah, I'm aware they're different. I just thought I'd need toric contacts to correct astigmatism, if I went that route. but could not find any due to my correction being so low - apparently, that's below below .50, I simply don't need torics and regulars will work fine, as you said.

That's great, as toric contacts were a lot more expensive and generally why I figured I should just go with ortho-k over the long term. As I can't use it without overcorrecting into farsightedness, and I can use the cheaper contacts, that will most likely work. Will just need to buy a pack in my prescription and give them a try and see how I like them.

RE the lightbulbs: thanks for the reassurance. I was just worried because I'm using multiples of very bright ones, and yes, looking at them is very uncomfortable and leaves me with  afterimages for quite a few minutes, so I was just worried over the long term it may cause some damage.

A lux meter records about 1500 or in the direct line of sight of the bulbs from below if I happen to glance up (low ceiling, unfortunately), and in the range of 100-200lux around the room depending on if the meter is in direct line of sight of one of the bulbs.

[JohnHaganMD]

If it bugs you modify your work environment, change position of lights, change type/power of lights or all else fails wear a baseball cap with a visor.