It is equal to half of the cylindrical power plus the full spherical power of the spectacle lens, i.e., the sphero-cylindrical lens dioptric midpoint. It indicates the spherical lens, which puts an astigmatic eye in a position of meridional balance.
It is equal to half of the cylindrical power plus the full spherical power of the spectacle lens, i.e., the sphero-cylindrical lens dioptric midpoint. It indicates the spherical lens, which puts an astigmatic eye in a position of meridional balance.
