Pinhole glasses are based on the principle of natural reflexes as the same effect is achieved when you squint to try and see more clearly. Your eyelids close around the top and bottom of your eyes, filtering out light rays reaching your pupil from these angles. Only light from your central area of vision and to the left and right sides can now enter your eye. The image you see is often sharper with a greater depth of resolution, and is generally brighter as there is a narrower range of light levels to contrast against each other. Wearing pinhole glasses is of course much less stressful on the eye than squinting, and is far more efficient at blocking extraneous light rays to produce a sharper and brighter image on your eye.
How pinhole glasses work
To fully appreciate how pinhole glasses work it is necessary to understand how the eye processes light rays to form an image.
How the eye works:
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Light enters through the cornea - a convex transparent membrane that covers the eyeball. Its curved shape allows light entering from different angles to be concentrated into a beam of light that enters the pupil.
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The pupil regulates the amount of light that enters the eye, and passes the beam of light into the lens
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The lens focuses the beam of light through the vitreous humour and onto the retina near the back of the eyeball. The ciliary muscle controls the lens so to give it the right shape to enable exact focusing of the image on the retina.
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On reaching the retina, that is the part of the eye that is actually sensitive to light, it transmits the information to the optic nerve, which in turn sends the image to the brain.
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