Odokotela bamehlo bavame ukuphonsa ngegama elithi "20/20" kancane kancane. Ngokuvamile, ngaphandle kokucabangela, odokotela bezilingo nezokunakekelwa kwamehlo basebenzisa leli gama 20/20 ngaphandle kokufundisa ngempela iziguli zabo ngalokho okushiwo empeleni. "Mnu Smith, unombono we-20/20 ... akuyona into enhle kangaka? "Iningi liye laqonda ukuthi ukubonwa kweminyaka engu-20/20 kwanele, kuvamile noma okungenani into enhle.
Njalo ubukela uhlelo lwezindaba, 20/20? Igama elihle lombukiso wezindaba ohlose ukukhanyisa noma umbono ocacile kakhulu ezindabeni ezithile eziphathekayo.
Ukulinganisa Umbono
Umbono womuntu uyinkimbinkimbi. Umbono wethu unamakhono amaningi kodwa izisebenzi zokunakekelwa kwamehlo zidinga indlela ethile yokulinganisa noma ukukala umbono. Uma singakwazi ukulinganisa umbono, singatshela ukuthi kude kangakanani nokujwayelekile okungenzeka kube khona noma ukuthi ukulungiswa kumele kubekwe kanjani ukuletha umuntu othize kulokho esikubheke njengombono ovamile. Kungaba nzima ukuhumusha umbono uma nje sitshele ukuthi, "Umbono useduze nendawo evamile" noma "Umbono ubonakala ulungile." Lokho ngeke kube yindlela efanele yokurekhoda ukuhlolwa kwethu. Kungaba nembile kakhulu ukurekhoda umbono womuntu njengo-20/30. Ngale ndlela, singakwazi ukulandelela isikhathi esithile ukuthi umbono wethu ungase ungashintsha kanjani noma ungashintshi kanjani.
Uhlelo lwe-Snellen lwe-Visual Acuity
Ukumangala kwabantu abaningi, ukuhlolwa kwamehlo kuyinkimbinkimbi kakhulu.
Ngenxa yokuthi iso lakho nombono uyingxenye yobuchopho bakho nesistimu yezinzwa, kukhona izinto eziningi ohlwini lwakho lokuhlola lokudokotela. Okokuqala futhi mhlawumbe isilinganiso esibaluleke kunazo zonke yimbono wethu oyinhloko, noma ubumbano obubonakalayo obuphakathi. Lona yingxenye yombono wethu esiwusebenzisayo uma sihlose iso lethu ngqo kulokho okufanele sikubuke.
E-United States, sisebenzisa isimiso se- Snellen se-acuity ebonakalayo. Inombolo ephezulu, engu-20, ibhekisela ebangeni lokuhlola elijwayelekile ezinyaweni. Ososayensi banquma ngamamitha angu-20 ngoba noma yini esiyibukayo engamamitha angu-20 noma ngaphezulu ibhekwa njengama-optical infinity. Bafika kuleso siphetho ngenxa yendlela indlela amaza ahamba ngayo nendlela amehlo ethu agxila kuyo izinto. Ngeso elivamile, elisezingeni eliphelele elisezingeni eliphezulu lomuntu, isisindo sokugxila sisesimweni esikhululekile lapho sibheka izinto ezinyaweni ezingama-20 noma ngaphezulu. Uma izinto ziqala ukusondela eduze kwamehlo ethu kunamamitha angu-20, iso lethu liqala ukushintsha ukugxila kwalo ukuze lihlale licacile.
Futhi, isimiso se-Snellen sicabanga ukuthi iso elivamile linomsebenzi omuhle uma lingakwazi ukuxazulula imininingwane ethile encwadini kumamitha angu-20. Lezo zindaba zichazwa ngokuthi ibanga lapho ingxenye ngayinye yencwadi, ngokwesibonelo, incwadi E, inokuphakama kwe-angular yomzuzu owodwa we-arc. Umzuzu owodwa we-arc ulingana no-1/60 wezinga. Yonke le ncwadi yenza imizuzu emihlanu ye-arc. Ukuze uqonde lokhu, kufanele ubuyele emuva kwejometri futhi udwebe unxantathu futhi ulinganise i-angle yengxantathu. Ukuphela okukhulu kwenxantathu kuyinhlamvu E, enezici ezinhlanu ... ibha yokuphezulu ye-E, isikhala, ibha eliphakathi, isikhala nesobunxele beso.
I-angle yimizuzu emihlanu ye-arc yencwadi yonke nomzuzu owodwa we-arc kubha ngayinye.
Ngakho-ke kusho ukuthini i-20/400?
Isibonelo, inombolo ephansi esikhathini 20/400 ibanga lapho imininingwane yohlu ngalunye ifaka iminithi eyodwa ye-arc. Ngakho-ke, lapho umuntu ema 400 amamitha ukusuka e-E enkulu eshadini leso, isici ngasinye se-E senza umzuzu owodwa we-arc. Lokhu kwaba yindinganiso ngoba iso lomuntu nezinhlelo zezinzwa ebuchosheni zisenza sikwazi ukubandlulula kalula phakathi kwezinhlamvu ezinezici ezithinta umzuzu owodwa we-arc.
Enye indlela yokucabanga ngalokhu kusho ukuthi uma umuntu elinganiswa ukuba nombono we-20/50, lowo muntu kufanele athuthele kufike ku-20mitha ukuze akwazi ukuxazulula imininingwane encane kunobhala, kanti umngane wabo ojwayelekile angama emuva emuva ngezinyawo ezingu-50 futhi uxazulule imininingwane encane kakhulu.
Ukusebenzisa izibuko ezigumbini zokuhlola
Uma ucabanga ngakho, iningi lamakamelo okuhlola ama-optometrists asetshenzisiwe awayizinyawo ezingama-20 ubude. Ngokuthakazelisayo, ukumisa nje isibuko kufana nokulinganisa ubude obude obuyizinyawo ezingu-20. Uma igumbi lingamamitha ayishumi ubude, ukubeka isibuko ukuphanga ishadi lesiso kwenza igumbi libonakale ngamamitha angu-20 ubude. Ama-optometrists athole kahle kakhulu ekulinganiseni amashadi e-eye ngokusho ibanga eliqondile lisuka kweso lesiguli esibukweni bese esuka esibukweni eya kumklamo weshadi lesiso. Ngokufika kwamashadi e-iso ekhompyutheni, ukulinganiswa kulula nakakhulu.
Ingabe 20/20 Ngokwejwayelekile Ngempela?
Kumele sinqume umbono we-20/20 ukuze sibe umbono ovamile. Kodwa-ke, njengamanani amaningi ekunakekelweni kwezempilo, kukhona "ububanzi" obuvamile bombono. Abanye bethu bangase babone okungaphansi kuka-20/20, bathi 20/25, kanti abanye bethu bangabona kangcono kunama-20/20, bathi 20/15, futhi babhekwa njengento evamile. Amashadi amaningi amaso akhelwe ukuhlela usayizi wezinhlamvu kuze kube phansi ngo-20/10, njengoba kungavamile ukuthola umuntu obona kangcono kune-20/10. Ukuxazulula umbono wethu oyinhloko kufana nokuqapha kwekhompiyutha ephezulu. Uma amaphikseli emuhle kakhulu futhi eseduzane ndawonye, ​​ukuxazulula kokuqapha kungcono. Abakhiqizi be-TV empeleni bahlola ubuciko bokubukwa . Kukhona iphuzu lapho isinqumo esithile se-TV esiphezulu kune-acuity engcono kakhulu yabantu ebonakalayo ngeke kwenze umehluko. Uma ukulungiswa kwe-TV kungcono kunalokho iso lomuntu elikwazi ukuxazulula, yini iphuzu?
I-SOURCE: Izinqubo zemitholampilo ku-optometry, i-Eskridge, i-J, u-Amose, uJ., Bartlett, J., uJB Lippincott Company, ngo-1991.