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pinhole glasses

Pinhole glasses, also known as stenopeic glasses, are eyeglasses with a series of pinhole-sized perforations filling an opaque sheet of plastic in place of each lens. Similar to the workings of a pinhole camera, each perforation allows only a very narrow beam of light to enter the eye which reduces the size of the circle of confusion on the retina and increases depth of field. In eyes with refractive error, the result is often a clearer image. Unlike conventional prescription glasses, pinhole glasses produce a clear image without the pincushion effect around the edges (which makes straight lines appear curved). While pinhole glasses are useful for people who are both near- and far-sighted, they are not recommended for people with over 6 diopters of myopia . It should also be noted that pinhole glasses reduce brightness and peripheral vision, and thus should not be used for driving or when operating machinery.

Pinhole glasses have been marketed by various companies on the claim that—combined with certain eye exercises—they could permanently improve eyesight. These claims have been analyzed, but no scientific evidence has been found to support them, and the claims are no longer allowed to be made in the United States under the terms of a legal settlement with the Federal Trade Commission.

The pinhole occluder, a device used by ophthalmologists for diagnosis of refractive errors, works on the same principles, but is not intended for use outside of diagnosis.

As viewing through a pinhole can much improve clarity of vision of people with refractive error, in an emergency a clear view can sometimes be obtained by looking through a single improvised pinhole.