Oogqirha bamajoni bavame ukuphosa ngekota elithi "20/20" kakhulu. Ngamaxesha amaninzi, ngaphandle kokucinga, oogqirha beziliso kunye neengcali zokunakekelwa kwamehlo basebenzisa i-20/20 kwikota ngaphandle kokufundisa ngokwenene izigulane zabo malunga noko kuthetha oko. "Mr. Smith, unomboniso we-20/20 ... akunjalo? "Abaninzi baye baqonda ukuba ukuba nombono we-20/20 uwanele, ngokuqhelekileyo okanye ubuncinane into enhle.
Ngaba ninakuze nibukele inkqubo yeendaba, 20/20? Igama elihle lomboniso weendaba ezijolise ekukhanyiseni okanye ukujonga ngokucacileyo kwiibali ezithile.
Umbono olinganayo
Umbono wabantu unzima. Umbono wethu uninzi kodwa abaqeqeshi beziliso bamehlo badinga indlela ethile yokulinganisa okanye ukulinganisa umbono. Ukuba singakwazi ukulinganisa umbono, sinokuxelela ukuba kude kangakanani na okuqhelekileyo okanye nokuba kukulungelelaniswa kangakanani ukuba kuveliswe umntu othile kwizinto esizicingayo njengombono oqhelekileyo. Kuza kunzima ukutolika umboniso ukuba sathi nje, "Umbono usondele ngokuqhelekileyo" okanye "Umbono ubonakala ulungile." Akunakuba yindlela efanelekileyo yokurekhoda uviwo lwethu. Kuya kuba nokuchanekileyo ngakumbi ukurekhoda umbono womntu ngo-20/30. Ngale ndlela, siyakwazi ukulandelela ixesha elithile indlela umboniso wethu onokuthi ungatshintsha ngayo.
Inkqubo yeSunellen ye-Visual Acuity
Ukumangaliswa kwabantu abaninzi, ukuhlolwa kwamehlo ngokubanzi kunzima.
Ngenxa yokuba iso kunye nombono wakho uyingxenye yengqondo yakho kunye nenkqubo yomnyuba, kukho izinto ezininzi kwiluhlu lokukhangela ugqirha. Okokuqala kwaye mhlawumbi umlinganiselo obaluleke kakhulu ngumbono wethu ophakathi, okanye ubumbano obubonakalayo. Le nxalenye yombono wethu esiwusebenzisa xa sijolise isohlo lethu kwinto ethile ukuyijonga.
EUnited States, sisebenzisa inkqubo ye- Snellen yobuninzi obubonakalayo. Inombolo ephezulu, i-20, ibhekisela kumgama wokuhlola oqhelekileyo kwienyawo. Izazinzulu zenze isigqibo malunga neenyawo ezingama-20 kuba nantoni na esiyijongayo i-20 okanye ngaphezulu ingathatyathwa. Baya kuleso sigqibo ngenxa yokuhamba kwamaza okukhanya kunye nendlela amehlo ethu agxila ngayo izinto. Kwijiso lomntu eliqhelekileyo, elisoloko ligqibeleleyo, i-muscle ekugxilwe kuyo yindawo ekhululekile xa ibukela izinto kwii-20 okanye ngaphaya kweenyawo. Xa izinto ziqala ukusondela kwamehlo ethu ngaphezu kweenyawo ezingama-20, iso lethu liqala ukuguqula ingqwalasela ukuze lihlale licacile.
Kwakhona, inkqubo ye-Snellen ithatha ukuba iliso eliqhelekileyo linobuncwane obufanelekileyo xa liyakwazi ukulungisa iinkcukacha ezithile kwileta ngeenyawo ezingama-20. Ezi nkcukacha zichazwe njengomgama apho ngalinye iqela leleta, ngokomzekelo, ileta E, inokuphakama okwangomzuzu omnye ngomzuzu. Omnye umzuzu we-arc ulingana no-1/60 we-degree. Incwadi yonke ibumba imizuzu emihlanu ye-arc. Ukuze uqonde oku, kufuneka ubuyele kwijometri uze udwebe unxantathu uze ulinganise i-angle yengxantathu. Isiphelo esikhulu senxantathu yileta E, enezinto ezinhlanu ... ibha ephezulu ye-E, isikhala, ibha engundoqo, isikhala kunye nebhasi ephantsi kweso.
I-angle yimizuzu emihlanu ye-arc kwileta yonke kunye nomzuzu omnye we-arc kwibha nganye.
Ngako-ke i-20/400 ithetha ntoni?
Ngokomzekelo, inombolo ephantsi kwikota 20/400 ngumgama apho iinkcukacha zetekisi nganye zifaka enye iminithi ye-arc. Ngoko ke, xa umntu ema 400 iinyawo ukusuka kwi-E enkulu kwi-chart yamehlo, isakhi ngasinye se-E sichaza umzuzu omnye we-arc. Le nto yaba ngumgangatho kuba iso lomntu kunye neenkqubo ze-neurological engqondweni zenza ukuba sikhewule ngokucacileyo phakathi kweencwadi kunye neempawu ezingaphaya komzuzu omnye we-arc.
Enye indlela yokucinga ngale nto kukuthi ukuba umntu ulinganiswa ukuba abe nombono we-20/50, ngoko ke lowo mntu kufuneka aphakamise ukuya kwii-20 ezinyawo ukuze akwazi ukucombulula iinkcukacha ezincinane kunobumba, kanti umhlobo wabo oqhelekileyo unokuma indlela yokubuya emva kweenyawo ezingama-50 kwaye usombulula inkcukacha encinci.
Ukusebenzisa izibuko kwiiNkonzo zokuHlola
Ukuba ucinga ngako, ininzi yamagumbi okuhlola optometrists ayisebenzanga ngamawaka angama-20 ubude. Okuthakazelisayo, ukumisa nje isibuko kufanekisela umgama wokuvavanya ubude obude obu-20. Ukuba igumbi linamamitha alishumi ubude, ukubeka isibuko ukuphinda isicatshulwa kweso senze ukuba indawo ibonakale iinyawo ezingama-20 ubude kwiso. I-Optometrists iye yafika kakuhle kakhulu ekukhawuleni amashadi yamehlo ngokuhambelana nomgama ochanekileyo kwiso lesigulane ukuya kwisibuko uze uvela kwisibuko ukuya kwiprojekti yetshathi yeliso. Ngokuza kweetekisi zamehlo zekhompyutha, ukulingana kulula ngakumbi.
Ngaba 20/20 Ngokwenene?
Simele sibone umboniso we-20/20 ukuba ube ngumbono oqhelekileyo. Nangona kunjalo, njengemilinganiselo emininzi kwiinkonzo zempilo, kukho "udidi" oluqhelekileyo lwemibono. Abanye bethu banokubona ngaphantsi kwe-20/20, bathi 20/25, kwaye abanye bethu bangabona bhetele ngaphezu kwe-20/20, bathi 20/15, kwaye bajongwa njengesiqhelo. Uninzi lweetrakthi zamehlo zenzelwe ukucwangcisa ubungakanani betawubanzi ukuya phezulu nge-20/10, kuba akunqabile ukufumana umntu obona ngcono kunama-20/10. Isisombululo sombono wethu ophakathi sifana ne-computer-resolution solution. Ukuba iipekseli zilungile kakhulu kwaye zivalelwe kunye, isisombululo sesondlo silungile. Abavelisi beTV bakubonayo ubunzima bokubukeka . Kuba ngumbono apho isisombululo esithile seTV ephakamileyo kuneyona nto ibonakalayo ebomntu ayibonayo. Ukuba isisombululo seTV si bhetele kunokuba iso iso lomuntu lingasombulula, yintoni na into?
I-SOURCE: Iinkqubo zeklinikhi kwi-optometry, i-Eskridge, J, uAmosi, uJ., Bartlett, J., uJB Lippincott Inkampani, ngo-1991.