Incazelo: Emmetropia yigama elisetshenziselwa ukuchaza umbono womuntu lapho kungekho nhlobo iphutha lokuphikisa noma ukugxila ekugxilweni. U-Emmetropia ubhekisela esweni elingenalo ukukhubazeka okubonakalayo. Izithombe ezenziwe kweso le-emmetropic zigxile ngokuphelele, zicacile futhi zicacile.
Amehlo anemmitropia awadingi ukulungiswa kombono . Uma umuntu ene-emmetropia emehlweni womabili, lowo muntu uchazwa njengombono ofanele.
Uma iso liyi-emmetropic, imisebe elula efika iso kusukela kude ibheke ekuhloleni okuphelele kwi-retina.
Uma ilanga liwubude obungavamile noma i-cornea ingumumo ongavamile, kungenzeka ukuthi ngeke ube yi-emmetropic. Uma iso lomuntu lide kunesilinganiso, ukukhanya kungahle kugxilwe phambi kwe-retina esikhundleni ngqo kuwo. Lokhu kungabangela ukusondelana. Uma ibhola lomuntu lifushane kakhulu, izithombe zigxilwe ngemuva kwe-retina. Lokhu kubangela ukubhekwa phambili.
Isimo esiphezulu se-emmetropia noma ukuthi iso lithinta kanjani izithakazelo zesayensi kanye nezodokotela zamehlo. Ulwazi lokuthi umntwana okhulayo ukhula kanjani ekuboniseni imfucuza kuyoba nethemba ukuthi uzobabonisa izindlela ezintsha zokulungisa amaphutha okuphika, njengokubheka eduze nokubukeka kahle noma ukusiza ukuthola izindlela zokuvimbela ukwanda kwamaphutha okuphika. Inqubo ye-emmetropization ayiqondakali kahle kodwa kucatshangwa ukuthi ivela ngokufaka okubukwayo, umsebenzi wobuchopho, izakhi zofuzo kanye nezinye izindlela lapho i-defocus ingathinta ukukhula kweso.
Uma ungenayo i-emmetropic, khona-ke unephutha lokubuyisa. Izibonelo zephutha lokubuyisa zilandelayo.
- Eduzane nokubona : Ukubukeka kweso, noma i-myopia, yisimo lapho izinto eziseduze zibonakala ngokucacile, kodwa ezikude zivaliwe. Ukuzibona ngeso lengqondo kungazuzwa njengefa futhi kuvame ukutholakala ngesikhathi seyingane. Kodwa-ke, ungahlakulela ukusondela ekutheni ukhulile. Abantu abahlakulela i-myopia lapho bekhulile kaningi abavame ukuhlakulela inani eliphakeme lokubona okuncane.
- Ukubhekela phambili : Ukubhekela phambili, noma i-hyperopia (futhi ebizwa ngokuthi i-hypermetropia), ngokuvamile kubangela izinto ezikude ukuba zibonwe ngokucacile, kodwa izinto ezivelele zibonakala zifakwe emaceleni. Ukubhekwa phambili ngokuvame ukugijima emindenini. Uma umuntu enamazinga aphezulu okubuka phambili, ukubuka kwabo kude kungase kufinyeleleke ngaphezu kombono wabo oseduze. Abantu abaningi baphoqa ukubhekwa phambili kwe-presbyopia, iphutha lokuqhathanisa ngokuvamile elivela eminyakeni engaphezu kwengu-40 ubudala.
- I-Astigmatism : I-Astigmatism ivele ivela lapho i- cornea ine-curvature engavamile. I-cornea igobile ngaphezulu kwesinye isiqondiso, okwenza kube nombono ongenalutho. I-Astigmatism ingabangela umbono obonakalayo kuwo wonke amabanga, futhi ivame ukuvela kanye nokubona okude noma ukubona okuncane. Abantu abaningi bane-astigmatism encane kakhulu. Amanani amakhulu kakhulu njenge-astigmatism abangela ukuphazamiseka ngaphezu kwemibono ephazamisayo. Inani eliphakeme kakhulu le-astigmatism ngezinye izikhathi linenkinga enzima yokufinyelela umbono we-20/20.
- I-Presbyopia : I-Presbyopia inqubo evamile yokuguga kwe- lens iso. Ukulahlekelwa ukuqina kwe-lens eyenzeka ngokuguga, okwenza kube nzima ukugxila emigqeni eseduze. Ososayensi bakholelwa nokuthi ngaphezu kokulahlekelwa ukuqina kwe-lens, umsizi owenza i-lens ishintshe ukugxila, okuthiwa umzimba we-ciliary, uqala futhi ukusebenza. I-Presbyopia ivame ukuba yindalo ngemuva kweminyaka yobudala engama-40-45 kodwa abantu phakathi kuka 35-40 bangabonisa izimpawu zakuqala ngokuya ngesimo sabo sokubukwa, umsebenzi, nokuphila kwabo