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  1. ole timer

    ole timer Forum Owner Forum Owner

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    Vision
    We take our eyes for granted. However, in a survival situation we may have lost our glasses, or we may need to prevent snow blindness.

    Vision is something we often take for granted especially in outdoor situations. ANY SKILL (even well practiced skills) becomes very difficult without our eyes to help us along. I have often wondered how Native American and other primitive civilizations faired when faced with vision problems. Surely they had near-sighted and farsighted peoples right? Maybe they just delegated hand-skills such as basketry to those with Myopia (nearsightedness) and relied on those with Hyperopia (farsightedness) to hunt or scout. I find myself among the nearsighted group yet would not resign myself to only practice hand-skills if I lost my glasses in the woods and had to fend for myself.
    The solution is an application of physics, yet is not new at all. We see that vision correcting or vision protecting devices have been used by many ancient peoples. An example is the snow goggle used to reduce glare by the sun on the bright snow. The slits were basically mimicking our eyelids as we squint.

    Pinhole goggles so named for the small pinholes placed in a material to reduce excess light rays and assist in our eyes imaging of objects are a good solution to broken or lost glasses. Making them is a helpful skill to understand before you find yourself making them without glasses! They are essentially the same as primitive snow goggles but imitate the pupil’s ability to retract when focusing versus the eyelid as we squint.

    How Pinhole goggles work

    Pinhole goggles provide an endless depth of focus when the eyes are not correctly focusing by reducing the amount of excess scattered light rays to the retina. They are good for helping with refractive errors of the eye. A refractive error means that the shape of your eye does not bend light correctly resulting in a blurred vision.
    So lets get to work.

    Pinhole glasses can either be single holed or multiple holed. Many holes allow for more light and therefore easier to see but may limit the focusing.
    The holes should be about 1 mm in diameter (a typical trim nail is a good gauge) If multiple holes are placed just space them evenly and remember the goal is to minimize excess light.
    IMPORTANT - To get the spacing right for your eyes take a scrap strip of bark or paper and poke two holes estimating where your pupils are and the spacing between them. Do this as your starting place. This scrap should sit on the bridge of your nose where the goggle bridge sits. Looking through hole on the right as your “keeper” hole make additional holes in the left side until you can see through both holes comfortably. To be sure you have the proper position and spacing alternate closing each eye while looking through both holes. You should be able to close each eye without losing any of the image seen previous to closing the eye. In other words, make sure the focus of each eye is the same and that the holes allow equal view of that focus target. When you are confident place this strip as a template on the goggle fashion from almost any material and mark or drill the holes being sure the bottom of the strip is flush with the bottom of the bridge on the goggle.

    Snow Goggles
    On a sunny day in winter the sun reflects off the snow which can cause snow blindness, a debilitating and potentially dangerous condition which literally blinds a person for a few days. Snow goggles can prevent this from happening.

    Code:
    http://wildwoodsurvival.com/survival/winter/goggles/index.html