Eyes are an important asset to survival. In some cases of emergency, they will be the difference between life and death. So some thought should be given to protecting your eyes, and optimizing your ability to see.
What do you need to protect your eyes from? Basically, UV (Ultra Violet light), intense light (sun, reflections from snow or water), airborne particles (dust or sand) and occasionally, projectiles. For UV and intense lights, the obvious solution is sunglasses. Good ones block all UV and cut down most bright lights to a bearable level. If they are polarized, they can cut glare and may even help you to see into water to see what fish may be lurking there. Unfortunately, sunglasses are a bit bulky for some kits. One alternative is “flat” glasses such as the “I-Shield” (www.survivalmetrics.com). These are roll up sunglasses (available in dark and light versions; I suggest the dark) which are held on with a cord. A smaller (and cheaper) option is the “roll-up” sunglasses you get at the optometrist’s office after a dilation. These roll up and fit into a film canister (for you old timers), pill bottle or other container. To use them, unroll and let the ends press against your temples as they try to roll back up. Not terribly secure, but better than nothing and “free” to boot. I suspect some duct tape and paracord could help keep these glasses in place.
On the other hand, to protect against blowing dust or sand, goggles are the optimum solution. The best ones seal all the way around the eyes so no particles can get in. But again, many goggles would be too bulky for some kits. The surplus aviator ones I have are pretty compact. The front (lenses) are glass, connected by a hinge, and the rims are fur covered wire rings. The sides are nylon cloth. By pressing the rims toward the lenses, they flatten out pretty well. Ones like mine are not as available these days, but some (and reproductions) can be still found. This style of goggle seems popular with the “steampunk” crowd. Mine have dark lenses so they act as sunglasses as well.
“Safety glasses” offer protection against some projectiles, but generally there is not room for these in any but the biggest kits. By projectiles, I am not talking about bullets; there is not really any eye wear which can protect against them. More like BB’s, gravel, splinters of wood and metal and the like. Fortunately, these are less common hazards during survival situations.
To keep duplication of equipment to a minimum, you could look for goggles with tinted lenses, or minimum clearance sunglasses with side shields. To really cover the bases, see if “safety” rated lenses are available.
So far we have assumed that your vision is normal. In many cases, this is not a good assumption. Being able to see well will increase your ability to survive. It is a good bet that you normally wear glasses or contact lenses for the best vision; if so, you need to pay some attention to this in your survival preparations.
Contact lenses can be quite beneficial during normal circumstances, but can be a problem in a survival situation. They are small, fragile, sensitive to dirt and generally should not be left in the eye for days at a time. Although some lenses are “rated” for extended wear, even up to “30 days”, it is risky to wear any lenses overnight, and only by using the correct lens and “perfect” maintenance can the risks of temporary or permanent vision problems be minimized. This is usually not practical in a survival situation, so I suggest carrying a case to store your contacts in, and to remove them as soon into the situation as it is practical to do so. Which then leaves you with inferior vision.
If you wear glasses, the circumstances which plunged you into the survival situation may have led to the the loss or breakage of your glasses. Which also leaves you with inferior vision. Thus, carrying spare glasses is of value both for glasses wearers AND contact wearers. Unfortunately, as mentioned above, these can be too bulky for some kits. One option I’m tempted by is a pair of titanium folding glasses (from China). These would be about half the size of normal glasses. I don’t know how much I trust the lens makers there; I’ve gotten the wrong prescription locally; it would be a real chore if the pair from out of the country was not right. Perhaps I’ll order the frames and get the lenses locally.
Of course, if you wear glasses normally or as a backup to contact lenses, you need to rethink your “protection” methodology. Make sure your sunglasses/goggles will work with your glasses. One option is have sunglasses which “clip on” your glasses; another is photo chromatic lenses in your glasses, which darken in response to light. Conversely, you could consider replacing the lens in your protection with a prescription one. Or have a frame which mounts inside holding a prescription lens. A good option, if you have room for it, is goggles which fit over your glasses.
We have talked about “normal” vision. In some cases, “superior” vision will aid you during a survival situation. Of course, you probably have a Fresnel lens or other magnifier in your kit, for reading small print, dealing with splinters and starting fire. Most Fresnel lenses appear to be 2 to 3 power; higher power would be better if you can find it (6x is rumored, but I’ve yet to find one). In some kits I include a multi-lens folding magnifier to give me a range of powers.
In a perfect world, you would also have a good pair of binoculars to allow you to see into the distance, to aid in locating safety or resources. Such would be too big for most kits, but a possible alternative would be a small “monocular”; basically a tiny telescope. These are available in various powers, and decent ones are not outrageously expensive. The higher the power, the “further” you can see, but the “field of view” (width) you can see will be less, making finding something more difficult. Most “pocket” sized monoculars have a fairly small front or “objective” lens, which means that their ability to gather light is poor. To overcome that would require the size of the unit to be much bigger, and thus impractically large for most survival kits. This means that you need to be aware that your monocular will likely not work well in low light situations.
There are “straight” ones, which tend to be longer, and “prism” ones which simulate the same optical length by “folding” it using prisms or mirrors. I would say that the prism ones tend to be higher quality, but for your kit, go for what will fit. 10 x 25 (power x objective lens size in mm) seems about the biggest I’d look at. Although they now have variable power ones which might be worth a look. I’ve seen ads for a 10 – 30 x 25 which could be useful and the price is reasonable, but they do not specify the overall size which could be a deal-breaker. Size appears to NOT be commonly listed; this is something you will probably want to shop for locally. Then you can not only evaluate the size, but how usable it will be for you.
If the monocular concept just does not do it for you, and you have the space, there are some compact binoculars (basically 2 monoculars hinged together). Good ones tend to be pricey, though.