Pinhole glasses, also called stenopeic glasses, are eyeglasses with lenses that consist of many tiny holes filling an opaque sheet of plastic. These "pinholes" block indirect rays from entering the eye, thus preventing them from distorting your vision. While this does not actually improve the focusing ability of the eye, it does reduce the size of the blur circles so that reasonably clear vision may be achieved.
If you try on a pair of pinhole glasses, you may actually notice a slight improvement in your vision. However, while wearing the pinhole glasses, vision is quite obstructed by the black spaces around the pinholes. Most people would be reluctant to wear the glasses, as they are not very fashionable. Also, it should be noted that pinhole glasses reduce brightness and peripheral vision, and therefore are unsafe to wear while driving or operating machinery.
Pinhole glasses are mainly used by eye care specialists as a diagnostic tool. In almost all cases, other forms of correction will obtain clearer vision.
Source: Optometrists Association Australia. Pinhole Spectacles. Copyright 2008.
Optometrists Association Australia. Pinhole Spectacles. Copyright 2008.