Anyone who remains in this environment for long periods during the summer without protection can suffer from snow blindness. This painful condition forces the person to discontinue the use of the eyes until healing can take place. This is nature's way of protecting the eyes from permanent damage. Some advantages that pinholes have over prescription glasses. Bifocals or trifocals are designed to provide a clear image only at fixed distances.
Pinholes provide an improved image at ALL distances.
Multi-focal lenses provide a continuously variable curve that is supposed to give good vision at all distances. In reality, the distortion on either side of the center line is considerable and often too great for comfortable use. Pinholes eliminate this problem. There is no need to continually throw away old glasses and buy new, stronger ones. Unless the pinholes break, they can be used an entire lifetime.