Pinhole glasses

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.

Additionally, pinhole glasses reduce brightness and peripheral vision,[1][2] and thus should not be used for driving or when operating machinery.

This is because the eyelid moving over the pupil will reduce the amount of light falling onto the retina and thus will briefly remove the lateral inhibition effect which normally makes all the holes appear bigger (and the grating appear thinner).

[citation needed] Pinhole glasses have been marketed by various companies on the claim that—combined with certain eye exercises—they could permanently improve eyesight.

Due to a lack of formal clinical studies to substantiate this type of claim by companies selling pinhole glasses, this type of claim is no longer allowed to be made in the United States under the terms of a legal settlement with the Federal Trade Commission.