Kev txawj ntse xim hloov lub lens hloov nrog kev siv ntawm ultraviolet lub teeb, hloov kho xim qhov tob, ib daim iav yog ntau lub hom phiaj, tsis muaj teeb meem hloov pauv, sab hauv tsev thiab sab nraum zoov yooj yim dua, kev tiv thaiv qhov muag ntau dua.
Cov xim hloov xim ntse qhia pom cov qauv kev faib tawm, thaum raug ultraviolet irradiation, cov molecule cia li kaw los thaiv lub teeb nkag, siv nws zoo photoresponsiveness thiab colouring, sai teb rau lub teeb hloov, ntau npaum.