01 Ukongeza kokuchaneka kwayo, isixhobo sokulinganisa i-PH saziwa nangokuguquguquka kwayo. Ingasetyenziswa kuluhlu olubanzi lweendlela zamehlo kunye nobukhulu, ukuhlalisa iimilo zobuso ezahlukeneyo kunye nobukhulu.
Ngaphezu koko, esi sixhobo sidlala indima ebalulekileyo kwinkqubo yokufakwa kwamehlo ngokubanzi. Kunye neminye imilinganiselo enjengomgama we-pupillary, inceda oogqirha bamehlo benze isisombululo esibanzi samehlo esilungiselelwe iimfuno ezithile zomntu.
Isishwankathelo, isixhobo sokulinganisa ubude bomfundi sisixhobo esibalulekileyo koogqirha bamehlo kunye neengcali zokunxiba zamehlo. Ukuchaneka kwayo, ukuchaneka, kunye nokuguquguquka kwayo kwenza ukuba ibaluleke kakhulu ekuqinisekiseni ukuba iimpahla zamehlo ezichazwe ngugqirha zibonelela ngowona kulungiswa kombono kunye nentuthuzelo kumntu oyinxibileyo.