An I-auto refractometer isetyenziselwa ukujonga ukuhlangana kokukhanya emva kokungena kwi-eyeball.Isebenzisa imeko ye-emmetropia njengomgangatho wokulinganisa iqondo lomahluko kwi-vergence kunye nokusasazwa phakathi kweliso elihloliweyo kunye ne-emmetropia.Abanye bethu i-auto refractometer kunye ne-keratometer, i-keratometer isebenzisa iimpawu ezibonisa i-cornea ukulinganisa i-radius ye-curvature ye-cornea.