When you wear prescription glasses, your eyes are no longer able to use their focusing muscles to the fullest. These muscles begin to weaken, making it necessary to get stronger glasses over time. Pinhole glasses were designed to help reverse this slide and develop the eye muscles.
How do pinhole eye glasses work?
Pinhole glasses, sometimes known as stenopeic glasses, are made of an opaque substance like plastic or metal. You look through the many small holes in the material, which reduce the width of the diverging rays coming from the objects you are viewing (this is often called the pencil of light).
Ordinarily, light is admitted by the full opening of the pupil. Improper bending of the outer rays of the pencil of light causes errors like farsightedness, myopia, astigmatism and presbyopia to be more noticeable. In all these conditions, pinhole glasses can bring clearer vision. The pinholes block those outer rays, letting in only the rays which will pass through the center of the pupil so refractive errors aren't noticed so much.The pupil is open wide but the center is the only portion receiving light. This can lead to a striking improvement in visual acuity.