Troy,

Hehehe - this is more unimportant than 1095 vs 440C vs SV30 vs 357 vs 12 ga.. whatever the answer is, none of us can change our eyes out anyway, so why get excited about it in this venue? Learning to get the most out of what we have is far more relevant.

I wonder if there is a correlation between various reactions to my innocent comment and eye color.... nah, more wasted bandwidth.

Anyway, so far all I get are nothing more than what I already wrote; none make reference to specific source data. If there is a significant body of evidence, it most likely belongs to the USA DoD (could be any service, but I'll wager the Army would have had the broadest interest). I'm guessing that the data, if it exists, is in the mid-WWII to mid-VietNam date range - for what I hope are obvious reasons.

I'm going to bounce back to John and Avatar's questions and let more skilled/persistent searchers seek the truth on the matter of eye color (hope someone nails it down).

Tom

Jumping in here:

Sure, and everything I can type is readily available information and none of it is new - although it seems to be in danger of becoming forgotten information as more and more folks turn to light amplification devices - I have plenty of experience with those and they have their place. But I digress...

Caveat: Like making fire with friction, reading about "seeing in the dark" is absolutely not as good as being out in the dark with someone who can teach you.

OK - photopic, mesopic, and scotopic vision - fascinating stuff - let's call 'em "P", "M", and "S" for short.

P is daytime/ fairly high illumination and the cones do most, but not all, of the work. This is acute vision right in front of your focus. Cone = color vision and in this mode the rods main contribution is peripheral vision. You see color in front and B-W on the edges (your brain will be tricking you if you try to check this out, but you *can* prove it to yourself - no color available off on the edges - rods only come in one flavor)

S only uses the rods and they are completely absent in the center of your field of vision - that's retinal turf reserved exclusively for cones. So you have a total blind spot directly in the center of your field of vision that you use the most. Coping with that one issue effectively makes a HUGE difference for most people who feel that they simply cannot see at night. We'll come back to S in a moment.

M is relatively recently classified and explains away a few things that used to make folks like me go "Yeah, but sometimes I can see colors..." Essentially, M is a transitional mode that we use that involves enough light to stimulate the cones enough for our brains to notice but not so much that we totally overwhelm our rods. Deep twilight and early dawn are natural examples and for many of us, much more than a glimmer of moonlight on a clear night kicks this in. Without getting much into the color aspect of it, here's a simple test I use: If I can easily read a newspaper in moonlight, it's freaking bright out - for me, that's well under 50% illumination, but it varies from person to person. Proof that you are in M mode is that you can focus the print - S vision is horrible for acuity for obvious reasons. It also means that you've lost some of your dark adaptation, although it will come back more quickly once you get back into the gloom.

Bright moonlight (for me that means anything 1/4 or more) is fun while it lasts and I pay attention to moonrise/set/phase because while it knocks the snot out of my night vision, I can move through open areas as quickly as in daytime - YMMV, but it's awesome for everyone at some level of moonlight around 50% and up. OTOH, if there is a bright moon and you're mostly moving thru areas (like heavy canopy) where it's gloomy, the occasional patches of moonlight really screw you up. I have a really simple solution for dealing with that: I have an intense habit-turned-reflex to close my master eye tightly whenever light flares and only open it after the light dies out (bet you can guess where I developed that habit). One last thing - for M to really work in moonlight, you need to be in direct moonlight in all but highly reflective environments (like snow). Unlike daytime, there are pools of DARK under the trees... unless it's all snow covered and that's yet another topic in the saga (I have not found anything natural that's close to equaling snow cover, but others may know of similar environments).

See next post for more if interested.

OK - back to S: I'll hit a few things for you to work with, but there's more. Best to have a really good instructor with you, but give these a whirl: Oh - disclaimer - this has nothing to do with pilot issues (NVGs, instrument panel lights, glare, etc) - it's about being on the ground in the dark. Some of it is very relevant to being on the water after dark and some of it is true but irrelevent out on the water.

1. You cannot see anything directly in front of your field of vision. Forget it; you're totally blind there in S mode. If you're a ground-watcher when walking in the daytime, you're going to fall down a LOT walking around with S vision. Quit looking at the ground all the time.

2. You MUST look at things off-center - use the top, side, bottom of your field of vision. Around 20 degrees or a little less works best for most folks.

3. A tiny bit of light goes a long way with S - unlike cones, there are LOTS of rods feeding each optic nerve synapse - some say as many as 100 rods/nerve ending. That's a lot of additive input.

4. S is GREAT at detecting motion - it totally beats the snot out of P for motion detection. Use that. Stop, Look, Listen, smell, feel - do all that. Use the stops especially for detecting motion while you're really LISTENING - amazing what useful info you gather that way. Turn your head this way and that while you're doing this - even a nearly imperceptible breeze sounds like a gale in your ears, and it sems to automatically put the eyes into hyper-motion detecting mode.

5. CONTRAST - use the sky, use the variation between ground and trail and so on.

6. This is tricky and hard to explain/learn; it's also contradictory but true: If you stare (using the edge of your vision) at something in S mode, it washes out fairly quickly (rhodopsin, or visual purple, bleaches out FAST because it's so light sensitive). So you lose something you're intently studying... that's how a stump becomes a big fat racoon ot boogey man or - anyway, KEEP LOOKING, but ever so slightly twitch your eyes so you slightly shift the exact place the image is falling on your retina. Keep this up for more than 30 seconds and it will make you gasp - you can see the darned thing rather well! The best explanation I have heard is that our brain retains each slightly different image and uses them to build an accurate composite image. Which brings us to

7. PRACTICE - you're darned tootin' that we need to train our brains to show us what our eyes see and our optic nerve pre-processes. We get far more sensory input than we can consciously deal with and it's further complicated in S mode vision because suddenly other senses positively LEAP into the forefront, clamoring to deliver THEIR information. Don't discard that cool river of perfume running out of the short grass prarie that you just passed through, but also train your brain to better process the optic information you're getting - it is VERY different than the optic input you get almost all the time. We're clearly diurnal, but we can handle nocturnal pretty well with practice.

There is also very compelling evidence that after being in S mode for a few hours, all of a sudden our brain (or optic nerve or both) REALLY kicks in with the image processing, and the more often you use S mode the faster that kicks in. Caution: The opposite is true if you are exhausted to the point of being snoozy, at least in my experience. That's when the monsters start appearing in the darkness... shouldn't be moving then anyway, unless you're on some military marathon-death-march maneuver.

Ummm - did I mention that you simply must give yourself time to dark adapt? There are lots of techniques to help keep that time from being unbearably long, but even in the best of circumstances it takes at least 30 minutes to get to about 3/4 throttle in S mode. That's 30 minutes of no-BS DARK. If you've really been screwing your eyes up for days with bright sunlight you may be out of luck for geting anywhere better than about 10% - 25% of your basic capability working on a given night - guard your vision during the day if you know you're going to be out at night. It varies from person to person, of course.

Diet shouldn't matter for properly fed folks, but if you're vitamin A deficient, you're toast. Eat your veggies regularly - dark green leafy stuff and beta-carotine things (carrots, yellow-orange squash, etc.). But go easy on it - don't want Vit A poisoning, so just take in the normal healthy dose naturally.

A bright red light can DAZZLE you - make your pupils contract - but that will NOT wash out dark adaptation. Pupils dialate back open very quickly compared to your dark adaptation time. Rods are hyper sensitive to a short wavelength in the "green" range (around 510 nm wavelength), so if you use anything more than the faintest glimmer of green light, you will knock out your dark adaptation. There's a fine line there that I'll leave to the astronomers, who may need to use a glimmer of green for instrumental or map reasons, but for us woodshounds, stay away from anything but red. Look at a red Photon directly and you'll be dazzled. Shield it with your hand and direct the light at whatever you need to see and it will have no adverse impact.

Ach! There's more, but this post is already too long. Go practice! Walking with S mode vision fired up and humming just so totally beats the stuffing out of that little cone of light from a flashlight (torch) - you can only see where the light shines, have about nada for peripheral vision, and once you get it, you'll really HATE running into flashlight walkers. S mode gives your brain a huge panorama of visual input that you're largely unaware of during P mode vision. You can see things way off the sides... like I said, practice.

Again, remember that the words "acuity" and "scotopic" do NOT belong in the same sentance - the world is a bit fuzzy in S mode; maybe something like 20/200. And that is a good reason to wear clear eye protection if you're trudging down an overgrown gloomy path in the woods - you may very well be able to see everything quite well for your purposes, but that tiny little twig... there are techniques to spot those but that's more than I care to take on at a keyboard - best done close beside a person, pointing out things like that.

Which brings up a point - if you wear eyeglasses, they will be of comparatively little help in S mode for most folks, but they WILL protect your eye from casual twigs. If your uncorrected vision is pretty bad, leave them on even out in the open, because they will help up to a point.

Have fun <img src="/images/graemlins/cool.gif" alt="" />

Tom

Umm ... Err . .. OK .. but ... what about eye color? Curious minds and all.

And, by the way, thank you.

If you want to keep yoour night vision sharp, do not drink tonic water or drinks mixed with it.

I don't know anything more about eye color that what I already wrote, so... no one so far has turned up anything worthwhile one way or another yet on that subject. <shrug> I've been careful with avoiding the Pygmalion effect with scouts and adults and still my experiences follow that alleged fact. I searched for primary data hard enough to decide that it's either not readily available on the WWW and/or someone more skilled at searching than I will have to dig it up. All I've found is annecdotal, like my statement.

Tom

Eh? I didn't know that - the quinine in tonic water can cause slightly blurred vision and/or a temporary decrease in COLOR vision (cones; photopic vision) in SOME people (not all), which is why pilots are supposed to abstain from tonic water / quinine for 24 hours before flying, but I never heard or read anything about it affecting scotopic vision - where did you read that?

I like my occasional gin and tonic... or just plain tonic water. But I'll reconsider if it is surely known to adversely affect my night vision.

Regards,

Tom

UH, HUH. Excuses for ETOH consumption. Right.

As I understand the physiology, ETOH consumtion does not bother visual acuity, but interferes with occular movement -- hence the horizontal nystigmas[sp] test.

Well I can't find anything conclusive about eye color and night vision, but I did find this.
http://www.madsci.org/posts/archives/jul2001/994098545.Ge.r.html
This guy seems to think it is the exact opposite. I have actually heard that people with light colored eyes are more affected by bright sunlight, but I'm not sure about any of this night vision stuff.

I do know that some people seem to have poor night vision, but that is usually a cause of age. I think most people just don't know how to use their night vision because they never have had to.

This is a great topic though.

I beleive the legend about pale eyed people being more susceptable to bad things in the sun. I'm one of those 'pale eyed devils' of literature fame and I have had probelms when the brown eyed guy next to me did not.

Totally non-scentific. Anecdotal only.