Describing an optical device consisting of an opaque disk punctured with a fine slit or hole (or holes), which is placed in front of the eye in the same position as glasses and enables sharper vision in cases of gross far- or nearsightedness or astigmatism. It reduces distortion in the image formed on the retina because it confines the light reaching the eye to one or more fine beams. The same principle is used in the pin-hole camera.