Amachashaza Phambi Kwamehlo Akho?

Cishe uke wawabona—amachashazana ampunga avele aqhamuke esikhaleni phambi kwamehlo akho. Ungase uwabone lapho ufunda noma lapho ubuka udonga olunombala okhanyayo noma isibhakabhaka esicwathile.

UMA wake wazama ukugxila kwelinye lalawa machashazana, uyazi ukuthi ngeke ukwazi ukukwenza. Ukunyakaza okuncane kakhulu kwamehlo akho kuwenza anyamalale ngokushesha, futhi ngisho noma elinye lehlela ezansi nehlo, ngeke ukwazi ukubona ukuthi liyini.

Ayini la machashaza? Ingabe aphezu kwezinhlamvu zamehlo akho, noma angaphakathi? Cwayiza kodwa ungawanyakazisi amehlo. Uma la machashaza eshintsha eya kwenye indawo noma enyamalala, asuke ephezu kwezinhlamvu zamehlo, akuwona-ke lawo esikhuluma ngawo.

Kodwa uma kukhona umehluko omncane noma ungekho nhlobo, khona-ke angaphakathi, akuyi-vitreous humor, uketshezi olugcwalise ingaphakathi lenhlamvu yehlo. Njengoba engemuva kwe-lens yehlo, ahlala efiphele. Futhi njengoba i-vitreous humor iwujengezi olungajiyile kakhulu kunamanzi, angatshuza, aye le nale lapho uzama ukubona elilodwa ngokuqondile. Alithola kanjalo-ke igama lawo lesayensi yezokwelapha—muscae volitantes, okusho ukuthi “izimpukane ezintantayo.”

Avelaphi?

Avelaphi wona la machashaza? Amanye ayizinsalela ezasala phakathi nenqubo eyenzeka ngaphambi kokuba uzalwe. Uma umbungu usaqala ukukhula, ingaphakathi lehlo linemicu eminingi. Lapho umntwana ezalwa, le micu kanye namanye amangqamuzana kusuke sekushintshile kwaba yi-vitreous humor. Nokho, amanye amangqamuzana nemicu emincane kuyasala, bese kuzintantela ngokukhululekile. Kukhona nomgudu osuka kuyi-optic nerve uye kuyi-lens, kubantwana abangakazalwa unomthambo oya kuyi-lens ukuze uyondle. Lo mthambo uyadleka bese uyamunceka, ngokuvamile ngaphambi kokuzalwa, kodwa izingxenye ezincane zawo zingase zisale.

Kodwa kukhona neminye imithombo. Ngisho nakumuntu omdala, i-vitreous humor ayilona ujengezi yonke. Yembozwe ulwelwesi olukhanyayo oluthambile. Luncike kuyi-retina, ingxenye ezwela ukukhanya cishe eyemboze ingxenye enkulu yengaphakathi lehlo futhi emukela lokho okubonayo. Lolu lwelwesi olukhanyayo lunamathela kuyi-retina ngayo yonke indawo yalo engaphambili. Kulo mphetho kubenyezela imicu emincane kuyo yonke i-vitreous humor.

Lapho sikhula, le micu iqala ukushwabana. Lokhu kubangela ukuba eminye yayo yephuke. I-vitreous humor nayo iba namanzi kakhudlwana ukuze imicu ephukile ikwazi ukuntanta kahle kuyo. I-vitreous humor nayo iyashwabana kancane bese iqala ukuqhela kuyi-retina, mhlawumbe ishiya omunye udoti wamangqamuzana. Ngakho-ke lapho ukhula uzobona eziningana zalezi “zimpukane ezintantayo” zizulazula phambi kwamehlo akho.

Omunye umthombo walezi zintwanyana ezintantayo ungase ube imithambo yegazi ye-retina. Ukushayeka ekhanda noma ukucindezela kakhulu inhlamvu yehlo kungabangela umthambo omncane ukuba ukhiphe amangqamuzana egazi abomvu amaningi. Amangqamuzana abomvu ayanamathela, ngakho avame ukwakha isixha noma iketanga. Amangqamuzana angawodwa noma ayizixha angase aye kuyi-vitreous humor, futhi uma ehlala eduze ne-retina, angase abonakale. Amangqamuzana abomvu angase aphinde amuncwe umzimba, ngakho ekugcineni ayanyamalala. Nokho, lawa awavamile ukuba ama-muscae volitante ngoba abangelwa ukulimala okuncane.

Ingabe ukuba khona kwala machashaza kubonisa ukuthi kunokuthile okungalungile? Ngokuvamile akunjalo. Abantu abanamehlo avamile, ngisho nabasebasha, bayawabona, futhi kancane kancane bafunda ukungawanaki. Kodwa kunezimo ezithile ezingabonisa ingozi.

Uma Kunengozi Esongelayo

Uma ngokungazelelwe uqaphela amachashaza amaningi kunakuqala, lokhu kungase kusho ukuthi kunokuthile okungalungile okwenzekayo. Ikakhulukazi uma ubona ukubanika okuncane kokukhanya ngaphakathi kwamehlo akho. Lesi senzakalo sivela kuyi-retina, lapho ukukhanya kushintshwa khona kube ama-nerve impulse. Izinto ezintantayo eziningi kanye nokubanika kokukhanya kuvame ukubangelwa ukuhlukana kwe-retina. Kwenzeka kanjani lokhu?

I-retina inohlonze olunjengolwe-tissue paper emanzi futhi ithambe njengayo. Ulwelwesi lwayo oluthambile oluzwela ukukhanya luncike olwelwesini olungemva kwayo nasengxenyeni engaphambili kuphela ye-vitreous humor nakuyi-optic nerve, ngengxenye elula okuyiyona ebonayo. I-vitreous body isiza ekugcineni yonke i-retina isendaweni yayo. Ihlo liyakwazi ukumelana nezingozi kangangokuthi ngisho nokushayeka kakhulu akuvamile ukubangela i-retina ukuba ihlephuke noma isuke endaweni yayo.

Nokho, igalelo lingabangela ukulimala okwenza i-retina ibe buthakathaka endaweni ethile noma kubangele ukudabuka okuncane noma imbobo. Imbobo enjalo ingase ivele phakathi kwalapho kuhlangana khona i-vitreous humor ne-retina: Ukunyakaza ngokushesha noma ukulimala kwenza i-vitreous humor idonseke kanzima kuyi-retina, okubangela ukudabuka kancane. Uketshezi oluvela ngaphakathi kuyi-vitreous lungavuzela ngemva kwe-retina, luyikhuphule endaweni yayo. Lokhu kuphazamiseka kubangela amangqamuzana enzwa emukela ukukhanya ukuba adedeleke, futhi abonakala njengokubaniza.

Ukopha, okukhulu noma okuncane, ngezinye izikhathi kuhambisana nokuhlukana, ngoba ingxenye engaphakathi ye-retina inoxhaxha lwayo lwemithambo yegazi. Amangqamuzana egazi ayabaleka aye kuyi-vitreous humor, futhi abonakala njengenqwaba yezinto ezintantayo ezimane ziqhamuke esikhaleni. Ngokushesha ngemva kwalokhu, njengoba i-retina ihlukana, uvele wembozwe ubumyama.

Ngakho-ke, uma kwenzeka ubona inani lamachashaza landa, ikakhulukazi uma ehambisana nokubanika, hamba uye kudokotela wezifo zamehlo noma uphuthume esibhedlela! Kungenzeka ukuthi kuhlukene i-retina. Izinyathelo zokuyilungisa zingase zingenzeki ngemva kokuba i-retina isihlukene kakhulu.

Ingabe sekuyiminyaka ubona la machashaza emehlweni akho kodwa engahambisani nokubanika? Mhlawumbe akudingekile ukuba ukhathazeke. Cishe wonke umuntu uyawabona la machashaza. Uma ungawanaki, ngeke anyamalale, kodwa ingqondo iyafunda ukungawanaki njengoba uqhubeka wenza imisebenzi yakho yansuku zonke. Iqiniso lokuthi angaba khona ngaphandle kokuphazamisa ukubona liwubufakazi bokuklanywa kwehlo ngendlela yokukwazi ukuzivikela nokukwazi kwengqondo ukuvumelana nezimo.

Nokho, ngaphambi kokuba bathi asikho isidingo sokukhathazeka, abantu abanezinto ezintantayo kufanele bahlolwe ngudokotela wezifo zamehlo.

[Ibhokisi/Isithombe ekhasini 25]

Umsuka Wokulungisa Izinkinga Zokubona

Uma ufaka izibuko zamehlo ezigunyazwe udokotela noma ama-contact lens, kungenxa yama-muscae volitante. Ilukuluku lokwazi ngawo laholela uFrans Cornelis Donders, udokotela ongumDashi odumile wekhulu le-19, ukuba aqale ukucwaninga ngesayensi yokwakheka kwehlo neyezifo zalo. Ngaphezu kokuthola eminye imithombo yama-muscae volitante, wathola ukuthi ukukwazi ukubona izinto ezikude kuphela kubangelwa ukuncipha kwenhlamvu yeso nokuthi ukubona ngokufiphala kubangelwa izindawo ezingalingani ze-cornea ne-lens. Ukuhlola kwakhe kwenza kwaba nokwenzeka ukusungula inqubo yokulungisa izinkinga zokubona ngokufiphaza imisebe futhi ngaleyo ndlela kwaba nezibuko zamehlo namuhla.

[Isithombe]

Ama-“donder”

[Umthombo]

Courtesy National Library of Medicine

[Umdwebo ekhasini 24]

(Ukuze ubone ukuthi indaba ihlelwe kanjani, bheka encwadini)

I-“retina” ehlukene

Amangqamuzana abomvu

Ukudabuka kuyi-“retina”

Ulwelwesi oluthambile

I-“lens”

I-“pupil”

I-“iris”

I-“ciliary body”

I-“vitreous humor”

Imithambo yegazi

I-“optic nerve” eya ebuchosheni