I can't see things very well at a distance. I used to wear classes, then contact lenses, then nothing. I hadn't worn any corrective lenses for years because glasses were annoying and my contact lenses were messing up my eyes. One day I was thinking about the reason for near-sightedness and I figured that if it's caused by an inability of the eye's lenses to flatten out, then maybe I could physically assist them in some way instead of just optically correcting for the problem like 'corrective lenses' do. Then after trying some things I realized that I could pull back back on the skin at the sides of my eyes and this seemed to do the trick. Since then I've been in several seminars in which I successfully used this trick to be able to read the screen or chalkboard that was too far away for me to otherwise make out clearly. So I decided to make a simple device to do this for me. What I made probably wouldn't be something that most people would want to wear in public, but a professionally made, miniaturized version of such a device might have more widespread appeal, and it was fun to make and test in any case.
Note: Squinting is thought to work by decreasing the amount of light entering the eye as well as by slightly flattening the eye's cornea. The cornea is a lens of the eye that is responsible for a majority of the eye's focusing power. If one squints one can notice a decrease in the field of vision indicating a decrease in eye's aperture. However, when pulling at the eyelid corners with your fingers you will notice an enhancement of distance vision greater than that achievable by squinting, and without any noticeable decrease in field of vision. So it seems that this system works more by flattening the cornea than it does by decreasing the eye's aperture. A final possibility for how this system works is related to the eye's length: In near sighted people light from distant objects converges slightly in front of the retina (the part of your eye that actually detects the incoming light and sends the information to your brain). Using this system the pulling back on the eyelids may be compressing the eye slightly, thereby allowing the convergence of light rays to occur further back in the eye: at the retina, allowing clearer vision of the distant objects.
Step 1: Get the linear actuator
= The first photo shows a portable CD player, you could also take apart a non-portable CD player but those are usually a little harder to take apart.
= The second photo show the inside of a CD player. The black region on the green board on the left is what you're after, it has all the necessary motors and gears attached.
= The third photo shows this same mechanism from the underside, showing the motors and gears. You do not need to disassemble this mechanism, you will use it as is. All you need to cut are the wires leading to the rectangular motor (as noted on the photo).
Looking at the third photo: We'll be interfacing with the rectangular motor which is connected to the worm gear which is connected to the laser lense. The laser lense gets moved linearly, up and down along the worm gear. A 'worm gear' is the best way to allow low torque motors (such as the small rectangular one in the photo) to be used in high torque applications (like this one), but some cheaper CD players won't use worm gears. These alternate gear configurations will also work ok for this application.