Q: What is the normal range of auto refractometer?

A: Topcon KR-8900 autorefractometer works according to Scheiner's double pinhole principle [8]

and can measure the monocular refraction with a spherical range between -25.00/ +22.00 D in 0.12

or 0.25 D steps and a cylindrical range between -10.00/ +10.00 D in 0.12 or 0.25 D steps.