Pin hole can reduce refractive error upto -
Looking through a pinhole reduces the patients refreactive error and improves vision by increasing depth of focus. However, the pinhole vision is limited by diffraction. The opitimal apeure size of a pinhole is 1.2mm, which may correct up to 3D of refreactive error. Reference : Essentials of ophthalmology by Kaiser p.20
1 D
3 D
5 D
10 D
Optics and refraction