An auto refractometer waxaa loo isticmaalaa in lagu hubiyo isku dhafka iftiinka ka dib marka la galo isha isha. Waxay u isticmaashaa xaaladda emmetropia halbeegga si ay u cabbirto heerka kala duwanaanshaha dhabta ah iyo kala firdhisanaanta isha la baaro iyo emmetropia. Qaar ka mid ah our auto refractometer oo leh keratometer-ka, keratometer-ku waxa uu isticmaalaa sifooyinka milicsiga ee cornea si loo cabbiro radius of curvature of cornea.