Izinga le-substrate linquma ukuqina kwelensi kanye nokuthembeka kokumbozwa.I-substrate enhle ecacile futhi ekhanyayo, isikhathi eside sokusebenzisa futhi akulula ukuphuzi;Futhi amanye ama-lens awasebenzisi isikhathi eside kumbala ophuzi, noma amboze.Ilensi enhle ngaphandle kokuklwebheka, imihuzuko, indawo enoboya, i-pitting, i-lens oblique ukuhlangabezana nokubhekwa kokukhanya, isiphetho siphezulu kakhulu.Alikho ibala, itshe, umugqa, ibhamuza, ukuqhekeka ngaphakathi kwelensi, nokukhanya kuyakhanya.
Uma iphezulu inkomba ye-refractive, i-lens iba mncane, futhi intengo iphezulu.