Pinhole eyeglasses are another nontraditional method of vision correction. The glasses consist of a frame with non-prescription opaque lenses that have a pattern of many small (approx. 1 mm) holes (or "pinholes") for the wearer to see through. The pinholes can produce a reasonably clear image on the retina by allowing only a small portion of light rays that are reflected from an object to pass through small points on the lens. This eliminates most of the light rays that would remain unfocused by an eye that is nearsighted, farsighted, or has astigmatism.
(This same principle is in play when a person who needs corrective lenses squints when they don't have their glasses on. The squinting reduces the effective size of their pupil and limits the amount of unfocused light rays reaching their retina. The result: better vision!)
Eye doctors routinely use a pinhole lens to quickly gauge a patient's best achievable vision. If a person's vision improves when looking through a pinhole lens, their vision problem is probably due to an uncorrected refractive error. If the pinhole lens fails to improve their vision, an eye health problem, such as a cataract, may instead be the cause of their problem.
Some companies sell pinhole glasses, advertising them as miracle treatments or a "natural" alternative to conventional glasses. Unfortunately, though pinhole glasses can provides some improvement in functional vision, they cannot reverse nearsightedness, farsightedness, or astigmatism. And because they severely restrict peripheral vision, pinhole glasses should never be worn for driving.