Regarding the “How to survive without your glasses” post from contributor J.E. on Saturday August 23, those were all good tips, but some folks have sufficiently poor uncorrected vision that rough shapes and colors is all that can be detected beyond a few feet. Planning a self defense strategy with those limitations could wind up being hazardous to everyone around them, friend or foe.
Simple myopia (nearsightedness) can be at least partially overcome with magnifying lenses, which is what’s going on when J.E. suggests using binoculars in place of glasses. For those with astigmatism (distortions in the lens of the eye) and especially severe astigmatism, that trick doesn’t work very well.
What I suggest is obtaining multiple pairs of eyeglasses in one’s prescription. A couple of my local budget eyewear chains periodically offer “two sets of prescription eyeglasses for $99” deals. The frames offered on those deals will be ugly plastic ones, usually black or dark brown, and the deal will usually be for single-vision lenses– no bifocals. They’ll be glad to add bifocal (reading) capability, because the added options are where they make their money after getting you in the door with the $99 offer. (Other options include scratch resistant coatings, more attractive frames, replacement guarantees for breakage, et cetera.)
Get several “double pair deals” in your prescription during the sale, and don’t worry too much about the lack of bifocals. No-bifocal lenses will work fine for everyday distance sight, and a ten pack of plastic credit-card-size magnifiers can be had online for a few dollars to cover the reading portion. Stick-on plastic reading magnifiers can be had for under $20, trimmed with scissors and stuck to the bottom of your single-vision lenses. (Here’s a tip: They’ll come in pairs; use them one at a time and close the other eye while reading.)
The “$99 deal” will be for plastic lenses, which is fine and better than glass lenses, which can be easily broken. One upgrade they may offer is polycarbonate lenses, and if that upgrade is cheap enough, I’d suggest taking them up on it. Polycarbonate lenses are much tougher than plastic and lighter, because their different refractive index and material strength allows them to be a bit thinner, a bit more scratch resistant, and are what one finds in true safety glasses because it’s so tough. “Bulletproof” Lexan teller shields in banks are polycarbonate, just thicker. (Here’s another tip: Always clean plastic lenses, including polycarbonate, very gently under running water to minimize scratching.)
Because polycarbonate has a different refractive index, switching back and forth between regular optical plastic lenses and polycarbonate may cause some mild disorientation for a short time, as the eye accommodates the perceived distortion caused by the different refractive index between the two materials.
Tip: strong prescriptions can be thick, and the larger the lens, the thicker it will be at the edges, so those glasses will weigh more, sometimes enough more to be bothersome. Select frames with reasonable lens sizes– not too small as to limit correct vision, nor not so large the weight is an issue.
Tip: know the base curve of your finished lenses, something best determined by a competent optician. Base curve is the curvature of the external face of eyeglass lenses, which also determines the curvature of the internal face to correspond to your prescription. Changing base curves may introduce what the eye perceives as distortion, requiring an accommodation period. Once you find a base curve your eyes “like”, note it and order all your lenses with that base curve.
There are two basic types of temples– the eyeglass part on the sides that connects to the frame front (where the lenses are) and hook over your ears. Skull temples are angled down at the ends, usually about 45 degrees, and cable temples wrap completely around the back of the ear. Cable is preferred, because they won’t allow your glasses to slip forward as much when you’re sweating and looking down. Cable temples, and your ears, are still flexible enough to allow your glasses to be pulled off, as might happen if one falls into water from a boat. Cable temples are not common on eyeglasses, and frame manufacturers usually offer only a few styles with them.
The answer is sport-type elastic straps that fasten to the 45 degree bend in skull temples and go around the back of your head, available from most large sporting goods stores or online. You can go one step farther and get true sports eyeglasses, which have heavier frames and no temples at all, just the elastic straps. They will be pricey, though. I have two pair, which I use for strenuous activities; I can assure you, however, from my white water rafting experiences, that they still can and will be pulled off your head by rapidly moving water, never to be seen again. (The trick there, if you can manage it, is to pull them down off your face to around your neck, as the raft goes over. This way your odds on retaining them are better.)
Whatever spare glasses you obtain, wear each pair for several days to make sure the prescription and fit are correct. Keep them in hard clamshell cases to prevent breakage, and keep a copy of your prescription and soft optical-grade drying cloth in each clamshell case. Label each case with the date– “J Doe, 2014 spare”– so you know what’s in the case. Then, stash them among your emergency supplies.