Pinholes have been used to aid vision for hundreds of years. There is evidence that Eskimo communities have used fabrics and wood with narrow slits in as a primitive form of pinhole glasses, in order to protect their eyes from the glare of the sun off the snow and ice for many centuries. In the mid 20th Century, pinhole glasses for public use were pioneered. Although the first prototypes of pinhole glasses were unattractive, heavy and cumbersome to use, technological advances in materials, lasers and production methods have meant that the pinhole glasses of today are high-tech in comparison.

The medical profession too have adopted the science of pinholes as a way to measure visual acuity and to detect refractive vision disorders in their patients. Ophthalmologists often use a pinhole occluder to gauge visual acuity on a 20/20 or 20/50 scale, and also to determine the extent of a patient's refractive error (measured in diopters). This device is essentially a pinhole which is held very close to the patient's eye, and works on the principle that anything seen through a tiny hole will always be seen in focus. If the patient can see a target image through the pinhole more clearly than without the pinhole, then traditionally ophthalmologists prescribe eye glasses (logically, the ophthalmologist should prescribe pinhole glasses as he/she would have just proved that pinholes do improve vision!)

Honeycombing & Double Images

The science behind pinhole glasses is therefore proven by nature and approved by the medical profession. So why aren't pinhole glasses more popular? The truth is they are rising in popularity as more is understood about them. One great myth that needs to be exploded is that pinhole glasses do not work because of the honeycombing effect. This is when your eyes focus more on the opaque occluding plastic rather than the light rays passing through the pinholes, allowing you to 'see' the pinholes rather than the information transmitted through the pinholes.

Naturally, as with any new pair of glasses, your new pinhole glasses will take a little getting used to. Many people claim to be conscious of their eyeglass lenses and frames when they first wear them, but after a little time their brain gets used to the information it is receiving, so they notice the frames less. The same is true of the honeycomb effect. Providing you have a low refractive error then once you let your brain adapt to the improved visual information being received through the pinholes, then the honeycombing effect disappears! Honeycombing does become more of a nuisance at a higher refractive error index, and those with a refractive error of 6 diopters or more may find pinhole glasses impractical because of a persistent honeycombing effect.

The occurrence of double images is another factor that has historically deterred people from investing in a pair of pinhole glasses. However, with a greater understanding of how this happens we can see that as with the honeycombing effect, it only becomes a real problem for people who have a refractive eye disorder of 6 diopters or more.

Double images occur because light entering the minute aperture of the pinhole is slightly bent around the edges of the pinhole. This is known as diffraction, and happens to all light rays when they pass close to the edge of an object or opening. A well known example of diffraction is the swimming-pool phenomenon, when objects submerged in the water appear to be in a different location to where they actually are. This is because the water diffracts the light entering the pool, so the resulting reflection makes objects appear offset to where they really are.