An I-auto refractometer isetshenziselwa ukuhlola ukuhlangana kokukhanya ngemva kokufaka inhlamvu yeso.Isebenzisa isimo se-emmetropia njengezinga lokukala izinga lomehluko ekucineni nasekuhlakazekeni phakathi kweso elihloliwe kanye ne-emmetropia.Abanye bethu I-auto refractometer ene-keratometer, i-keratometer isebenzisa izici ezikhanyayo ze-cornea ukukala i-radius yokugoba kwe-cornea.