Intambwe igenda itera imbere yo kureba hejuru ya 40
Nyuma yimyaka 40, ntamuntu ukunda kwamamaza imyaka yabo - cyane cyane iyo utangiye kugira ikibazo cyo gusoma neza.

Igishimishije, uno munsi indorerwamo z'amaso atera imbere bituma abandi badashobora kuvuga ko ugeze "imyaka ibiri."

Iterambere ryiterambere - rimwe na rimwe ryitwa "nta murongo wa bifocals" - riguha isura yubusore ukuraho imirongo igaragara iboneka mumurongo wa bifocal (na trifocal).

Ibyiza bya lens igenda itera imbere hejuru ya bifocals
Bifocal eyeglass lens ifite imbaraga ebyiri gusa: imwe yo kureba hirya yicyumba indi yo kureba hafi.Ibintu hagati, nka ecran ya mudasobwa cyangwa ibintu biri mububiko bwibiribwa, akenshi bikomeza kuba bibi hamwe na bifocals.

Kugerageza kubona ibintu kuriyi ntera "intermedia" neza, abambara bifocal bagomba kuzunguza imitwe hejuru no hepfo, bagahindura bakareba hejuru hanyuma bakamanuka munsi yibice byabo, kugirango bamenye igice cyinzira ikora neza.

Lens igenda itera imbere yigana cyane iyerekwa karemano wishimiye mbere yuko presbyopiya itangira.Aho gutanga lens ebyiri gusa nka bifocals (cyangwa eshatu, nka trifocals), lens igenda itera imbere nukuri "multifocal" lens itanga iterambere ryoroheje, ridasubirwaho ryimbaraga nyinshi za lens kugirango zerekane neza mubyumba, hafi kandi intera zose ziri hagati.

Hamwe na lens igenda itera imbere, nta mpamvu yo kuzunguza umutwe hejuru no hasi cyangwa gufata imyifatire itoroheye kugirango ubone ecran ya mudasobwa yawe cyangwa ibindi bintu muburebure bwamaboko.

Iyerekwa risanzwe ridafite "gusimbuka ishusho"
Imirongo igaragara muri bifocals na trifocals ni ingingo aho hari impinduka zitunguranye mumbaraga za lens.

Iyo umurongo wambaye ibice bibiri cyangwa trifocal umurongo wo kureba ugenda unyura kuriyi mirongo, amashusho yimuka gitunguranye, cyangwa "gusimbuka".Kubura amahwemo biterwa niyi "gusimbuka ishusho" birashobora guterwa no kurakara byoroheje no gutera isesemi.

Iterambere ryiterambere rifite icyerekezo cyoroshye, kidafite imbaraga za lens imbaraga zo kureba neza kure.Lens igenda itera imbere itanga ubujyakuzimu busanzwe bwo kwibandaho nta "gusimbuka amashusho."

Lens igenda itera imbere yahindutse lensike ikunzwe cyane kubantu bose bafite presbyopiya yambara amadarubindi, kubera ibyiza byabo byo kwisiga no kwisiga kuruta bifocals na trifocals.