Nikeza uhlu olunezinhlamvu lwezinhlobo ezahlukene zamalensi
Context:Ukwakhiwa Kwamalensi Alula  Ama-lens amaningi angama-lens ayisiyingi: ama-surfaces awo amabili ayizingxenye zama-surfaces eziyindilinga. Indawo ngayinye ingahle ibe ne-convex (eqhuma ngaphandle kwe-lens), i-concave (ecindezelwe ngaphakathi kwe-lens), noma i-planar (iflethi). Umugqa ohlanganisa izikhungo zezinhlayiya ezakha ama-lens surface ubizwa ngokuthi i-axis ye-lens. Ngokuvamile i-lens axis idlula enkabeni ye-lens, ngenxa yendlela ekhiqizwa ngayo. Izibuko zingase zisikwe noma zigaywe ngemva kokukhiqizwa ukuze zibe nokuma noma usayizi ohlukile. Khona-ke i-axis ye-lens ingase ingadluli enkabeni ye-lens.  Ama-lens e-toric noma e-spheric-cylindrical anezinhlaka ezinama-radius amabili ahlukene okugoba ezindizeni ezimbili ezi-orthogonal. Anamandla ahlukahlukene okugxila kuma-meridian ahlukahlukene. Lokhu kwakha ilensi ye-astigmatic. Isibonelo yilensi yezibuko ezisetshenziselwa ukulungisa i-astigmatism esweni lomuntu.
Ngezansi kunezimo ezahlukene zamalensi: - I-convex: Igoba iphuma maphakathi ne-lens - I-concave: Ijika maphakathi ne-lens - I-planar: ilensi eyisicaba