That is, straight lines appear curved. This disturbing effect does not occur with pinholes. When you lay prescription glasses down improperly, they can easily get scratched at the center of the lens, the very area you have to look through. Scratching pinholes has no effect on their performance. Pinholes do not have to be cleaned of fingerprints and other marks that affect vision.
Pinholes are an easier thing to accept because they are the same for all ages.
Many people who have had corneal surgery find that their night vision has permanently deteriorated. Glare is a problem. Even in normal home lighting they have problems so that they get in the habit of turning on as many lights as possible in order to get a small pupil and reduce the visual problems. Pinholes, either conventional or Snap-ons, can deliver the same small pupil without increasing the electric bill. Children with special needs often use only their peripheral vision, and pinhole glasses help them concentrate on detail better.