Introduction: Post Apocalyptic Prescription Glasses (Updated)
So you're out in the wilderness, or downtown for that matter, and the unthinkable happens. Your glasses get destroyed, lost, or otherwise rendered unusable. What are you to do, surely you can't survive and thrive without being able to see clearly?
Fortunately for those of us with eyes that don't work correctly, there is a solution. By exploiting some simple(ish) physics we can get our vision back.
This works no matter what your prescription is, and can come in really handy day to day, or during a camping trip/survival situation.
Want to know how?
Using this exact same processes (with one minor adjustment) you can also make Glacier Goggles(really powerful sun glasses), which help prevent snow blindness and have been used by aboriginal peoples living in norther climates. I have made notes in the instructable for how to change these "glasses" into glacier goggles; these are indicated with italicized text.
//Edit Pilgrimm has some knowledgeable comments about the glacier glasses down in the comments section. //I'm thinking he(I assumed if I'm wrong please correct me) has more experience with them then I do. Head to the //bottom of the article and check them out.
//Another edit the first person who posts a "I made it" comment will get a free 3 month membership
Step 1: The Trick
So here is how to do it without any tools, or really any effort.
Wrap your index finger in a tight circle. Keep it there with your thumb, and get your other fingers out of the way. You want to get about 1mm(diameter) opening that lets light through.
Next close one eye, and holding you hand close to your open eye, look through this little aperture created by your finger.
You should be able to see everything (no matter the distance) in focus now.
//Edit:Tallwood2000 has suggested a method to use a pencil or pen instead of your fingers to make it easier look a //little less silly :) See the comments section for their description. Wobbler also has a neat trick that is easier on the //hands. Check them both out in the comments section.
Wow, how does that work?
Step 2: The Physics
So how can we replicate the intense machining that goes into creating modern optics with our index finger?
The truth is that we can't.
To understand what is going on we have to start with how our eyes work. All of our eyes, unless something terrible has happened, have a natural lens (a piece of tissue that is more dense than air but still transparent) that bends light into the back of our eye (retina). Now lenses can only focus light that comes from a specific distance; this is why pictures are out of focus when an object is too close to the camera. Now for our natural lenses, the lens in our eye is soft and can have its shape changed by muscles in the eye. This allows us to focus on things that are close to us, and things that are far away. Unless, of course, our natural lens isn't the proper shape. This makes everything blurry no matter how hard our eye muscles try to get things in focus.
So we have invented corrective lenses (glasses) that sit in front of our eyes and bend light in a way to counteract the irregularities that our natural lens has. Now our eyes can focus the light coming at them onto our retina, then our brain does its magic and we can see.
Now obviously you can't make a lens out of nothing just by bending your finger, unless you're a wizard/witch. So what are we doing?
The reason a lens can't focus objects from multiple distances is because it takes all the rays of light and bends them into a single point. This means that if those rays are coming from further away or closer than the focal length of the lens they won't converge at a single point. Instead, they'll be spread out in a shape larger than the object, resulting in a big, blurry, object-shaped smudge.
So what if we take all the rays coming in from different directions and get rid of them and just use one? We now no longer need to take a bunch of rays and converge them onto a single point. Instead, we just let that single ray hit anywhere on the lens and it will look like the object. This is what we are doing by making that really small hole with our finger, blocking all of those extra rays which need focusing and only letting "one ray" per object through. This allows us to see, in focus, what is around us despite our natural lenses being warped.
If it is this easy to correct blurry vision why did we go to all the trouble of making lenses in the first place?
As well as this simple trick works, there are some problems. You'll notice quite quickly that everything is significantly darker when you are looking through that little hole. Remember all those extra rays that we are blocking out? By blocking all of those we are drastically reducing the amount of light that reaches our retina, making everything darker. It is this that we exploit to make glacier goggles. You'll also notice that all depth perception is gone. It becomes really hard to tell how far away something is, especially if you don't know the size of the object already. So that is why corrective lenses are better, but they are way more difficult to make.
Now this is a really simplified explanation of what is really happening, because light isn't a ray, it's a wave, or particle, or both. But I will leave higher level physics classes to explain that to you, because I would probably not do that good a job.
Step 3: Materials You'll Need
As this is a survival project some of these following steps won't apply if you are making these in the field, but it should help as a reference.
Materials and Tools that You'll Need:
A piece of leather: Roughly the same size as your glasses (Mine is scrap from another project, but if you are out in the bush, a leather belt will work really well for this. Depending on your eyes and your belt you might be able to get away with using the section of belt that is perforated instead of punching your own holes)
A Knife: It will need to have a fairly small point on it to make the holes.
String or Twine: Or another method for attaching the "glasses" to your face.
Cutting Surface: I used a cutting board but anything you can cut the leather on will work.
That is all you'll need.
However if you want to make these look good...
A Measuring Device: This is to make everything symmetrical and square.
Leather dye: Add some colour (yes, I'm Canadian) to your leather, or make it look aged.
Eyelets: The holes last longer and not stretch out.
(If you are using eyelets you will also need: An eyelet punch and "anvil" (these usually come with the eyelets but not always), and a rubber or wooden mallet)
Step 4: Designing the Glasses
Start with a piece of paper, and using the knife poke some different sized holes in it. Experiment to find the largest hole that lets you focus, this will let in the most light and make these more functional.
Next you need to measure the distance between your eyes, I did this experimentally, but you can measure the distance between the center of your glass' lenses (this should also be on your prescription, should you have it handy). I poked a bunch of small holes in a piece of paper and determined which two fit the distance between my eyes. Remember that when you make this out of leather it is going to curve over your nose and take that into account when determining the distance between pupils.
//Edit:Pilgrimm has mentioned that using a slit instead of a hole will alleviate the need for this step, and allow //multiple users to use these "glasses". It will be more difficult to cut out of the leather though.
Now its time to figure out how big we need our piece of leather to be. Measure your existing glasses, or guesstimate by placing your hand across your face and measure the distance between your fingers. Same for the height of the band.
Once you have the rough dimensions they can be transferred to the leather.
Pencil works well, or you can lightly cut the marks in with the knife.
Edit// Based on the comments I have received I have updated the design of the "glasses". They now feature two slits //above and below the first pin hole, and another pin hole on the ear side of the first. These changes allow for greater //peripheral vision, without compromising the ability to focus.
Step 5: Cut Out the Leather
Once you have the marks on the leather you can begin to cut the piece out.
I used a leftover bit of a scrap piece I bought at Tandy Leather Supply. It is 5oz. vegetable tanned shoulder, I believe. The whole piece cost $23.99 (as evident in the photo) but the other project used the majority of it up.
Use the pocket knife and the ruler to cut out the leather in straight lines.
Once the leather is cut out, it's time to make the holes for the strap to go through.
On the edges of the short side, where the arms of your glasses would be, mark a place for a hole the same diameter as your string.
To make these holes you could use a leather punch; however it can be done quite easily with a pocket knife. Using the knife as a drill, rotate the cutting edge around in a circle. I put in two holes big enough for the eyelets that I am using.
// EditWobbler and michaellb2 have raised a good point, if you want to you can put in more holes. This will increase // your peripheral vision and allow more light in. There are actual glasses like this: link. Just be careful not to put them // too close together.
Next, if you have them, it's time to put in the eyelets. The eyelets will stop the cord from stretching the holes in the leather, they also add a professional look to the project. If you don't have them the "glasses" will still work just as well, so don't worry.
I put eyelets in with a screwdriver, rubber mallet, and the little "anvil" that came with the eyelet set. Starting with the screwdriver and a #4 Philips bit I punch twice per eyelet, rotating by 45 degrees each time, to bend over the edge. Then I use the spreading tool and the rubber mallet to more evenly bend over the edge. With this project the smooth side of the eyelets should face inwards towards you so that the bent over side doesn't scratch you.
Step 6: Wet Forming
In order to make these "glasses" contour to your face, and to block out more light, it helps to wet form the leather.
To do this dunk the leather in a bucket of warm water, let it sit for about 30 seconds so that it becomes pliable. Then place it against your face and mold it around your nose and the sides of your face. Make sure you have enough space your your eyes to open and close without your eyelashes getting in the way.
Make sure that the leather touches you face all the way around your eye socket so that no light gets in.
Leave it on your face for 3-5 minutes until the leather stops losing its shape when you take it off. When it maintains its shape you can take it off and let it dry, this will take a while.
Once it is dry you can dye it if you wish.
Step 7: Adding the Apertures
Now that you have your "glasses" formed to your face its time to make the apertures that will let you focus. Using the paper template from earlier, mark where the holes should be. Next, being very careful, use the knife to make little holes the same size as you did on the paper.
Make slits (~10mm x ~3mm) that you can see comfortably out of, but remember the bigger the opening the brighter and less effective they will be.
Step 8: Adding the Band
The wet forming will help the "glasses" fit your face, but in order to ensure that they stay there we are going to add a band.
To let the "glasses" be adjustable I tied one piece of twine to each of the two larger holes we put in earlier. I then tied the two pieces together using a system of knots that can slide but are also reasonably secure, called a clove hitch (see how to tie one here , we're using another piece of string rather than a wooden bar). Doing this twice, once for each side of the head, allows the knots to slide until they hit each other, making the "glasses" easy to tighten and loosen.
Alternatively you could just tie a length that is the same size as your head between the glasses.
Step 9: Final Remarks
Now you have a set of "glasses" that you can make, should your normal prescription ones get damaged. A useful skill to know if you, like me, depend on your prescription glasses to see the world clearly. Now as we have already discussed they have some limitations, which is why we had real glasses before.
These are not a replacement for corrective lenses. I will not be held accountable for anything that happens to you or that you do while wearing these. I do not recommend using these unless you really are SOL and desperately need to be able to see clearly.
I added dye and some tooling patterns to the "glasses" once they where done. I didn't show these in the steps because I didn't think it was necessary. I will however be writing another ible' soon which covers how to do that.
There are a few limitations while using these:
- The main one is the limited range of vision, reducing what you can see to two pinpricks can be quite dangerous, especially in our modern world.// This is reduced greatly by adding more apertures.
- The darkness caused by blocking out the majority of the light that enters your eyes.// Also reduced with more //apertures
- The loss of depth perception; this makes moving around while wearing them quite disorientating.//Still an issue
However, there are moments where you need to be able to focus:
- Being able to read would be the largest one: if you are on a trail and lose your glasses, reading the map for directions would be key to helping you survive.
- If you need to start a fire, being able to see fine detail (like for making a featherstick) would be a great help.
- Performing first-aid- even cleaning out a little cut is really hard if it's a big red blur.
I would use these only when I need to clarify something. Don't wear them all the time while you're walking around; I have, it's awful.
Hope you learned a new useful trick, but also that you never have to use it. If you liked this instructable please give it a vote by clicking the trophy in the top right corner. If you have any questions, please post a comment, or pm me. Thanks for reading- Lucas