A I-Lensmeter noma i-Lensocter, eyaziwa nangokuthi i-focimeter noma i-vertormeter, iyithuluzi le-opthalmic. Isetshenziswa ikakhulukazi ngabakwa-Optometrists kanye nama-Opticians ukuqinisekisa ukuthola umuthi ofanele ezihlokweni ze-eyeglasses, ukuze bakwazi futhi bamake ama-lens abhulofu, futhi baqinisekise ukubekwa kwelensi okulungile.