I-iris ingeyesistimu ebonakalayo yeso, ilawula inani lokukhanya elidlula kumfundi. Kuyingxenye enemibala yeso.

Iris iyinto yesibani seso, ingeyesikhumba sayo semithambo (ungqimba oluphakathi). Itholakala ngaphambi kweso, phakathi kwe-cornea nelensi, ekuqhubekeni kwe-choroid. Ihlatshwe maphakathi nendawo ngumfundi ovumela ukukhanya ukungena esweni. Isebenza kububanzi bomfundi ngesenzo semisipha ebushelelezi eyindilinga (imisipha ye-sphincter) nemisebe (imisipha ye-dilator).

Ukulawulwa kwabafundi

Iris iyahlukahluka ngokuvulwa komfundi ngokuthola inkontileka noma ukunwebeka imisipha ye-sphincter ne-dilator. Njenge-diaphragm esekhamera, ngaleyo ndlela ilawula inani lokukhanya elingena esweni. Lapho iso libona into eseduze noma ukukhanya kukhanya, izinkontileka zemisipha ye-sphincter: umfundi uyaqina. Ngakolunye uhlangothi, lapho iso libona into ekude noma lapho ukukhanya kubuthakathaka, imisipha ye-dilator iyasayina: umfundi uyanwebeka, ubukhulu bawo buyanda futhi buvumela ukukhanya okuningi kudlule.

Imibala yamehlo

Umbala we-iris uncike ekugxileni kwe-melanin, i-pigment ensundu, etholakala futhi esikhunjeni noma ezinweleni. Ukuphakama kokuhlushwa, mnyama amehlo. Amehlo aluhlaza okwesibhakabhaka, aluhlaza noma angama-hazel anokugxila okuphakathi.

I-Aniridie : kubangela ukungabikho kwe-iris. Kuyisici sofuzo esivela lapho kuzalwa noma ngesikhathi sobuntwana. I-pathology ejwayelekile, ithinta ukuzalwa okungu-1/40 ngonyaka. Inani lokukhanya elingena esweni alilawulwa: kakhulu, lingalimaza ezinye izakhiwo zeso. I-Aniridia ingaxaka i-cataract noma i-glaucoma, isibonelo.

I-Ocular albinism : isifo sofuzo esibonakala ngokungabikho noma ukunciphisa i-melanin ku-iris ne-retina. Kulokhu, i-iris ibonakala iluhlaza okwesibhakabhaka noma mpunga ngomfundi obomvu obonakalayo ngenxa yemithambo yegazi ebonakala ngokusobala. Lokhu kudilizwa kungenxa yokungabikho noma ukushoda kwe-tyrosinase, i-enzyme ebandakanyeka ekukhiqizweni kwezingulube ze-melanin. Izimpawu ezibonwayo ngokuvamile:

• i-nystagmus: ukunyakaza okuxakile kwamehlo
• photophobia: ukungabekezelelani kwamehlo ekukhanyeni okungadala ubuhlungu bamehlo
• ukwehla kwamandla okubuka: i-myopia, i-hyperopia noma i-astigmatism ingathinta abantu abane-albinism.

Lokhu kuchithwa kungathinta isikhumba nezinwele, sikhuluma nge-oculocutaneous albinism. Lesi sifo siholela esikhunjeni esihle kakhulu nezinwele ezimhlophe ezimhlophe noma ezimhlophe kakhulu.

IHeterochromia : okuvame ukubizwa ngokuthi “amehlo asodongeni”, akusona isifo kepha yisici somzimba esiholela kukwehluka okuyingxenye noma okuphelele kumbala we-iris. Kungathinta irises yamehlo womabili futhi ivele lapho kuzalwa noma kungavela esifo esifana ne-cataract noma i-glaucoma.

IHeterochromia ingathinta izinja namakati. Phakathi kosaziwayo, uDavid Bowie uvame ukuchazwa njengonamehlo amnyama. Kepha umbala onsundu esweni lakhe lesobunxele kungenxa ye-mydriasis engapheli, umphumela wokushaywa akuthola eminyakeni yakhe yobusha. I-Mydriasis ukukhuliswa kwemvelo komnyama ebumnyameni ukuletha ukukhanya okuningi ngangokunokwenzeka esweni. KuBowie, izicubu ku-iris yakhe zalimala ngokushaywa okwenza umfundi wakhe avule unomphela futhi aguqule umbala wamehlo akhe.

Azikho izindlela zokwelapha zalezi zifo. Ukuchayeka elangeni labantu abane-albinism kungadala ukulimala kwesikhumba futhi ingozi yabo yokuba nomdlavuza wesikhumba iphezulu. Ngakho-ke iWorld Health Organisation (WHO) (6) yeluleka ukuthi ungalokothi uziveze elangeni, kusukela ebuntwaneni. Kunconywa ukufaka isigqoko nezibuko zelanga kwazise i-iris eyonakele ayisadlali indima yayo njengesithiyo emisebeni yelanga ye-ultraviolet.

I-Iridologie : ngokwezwi nezwi "ukutadisha iris". Lo mkhuba uqukethe ukufunda nokutolika iris ukubona isimo somzimba wethu nokwenza isheke lezempilo. Le ndlela ephikisanayo ayikaze iqinisekiswe ngokwesayensi ngocwaningo.

I-biometrics kanye ne-iris identification

Iris ngayinye inesakhiwo esihlukile. Amathuba okuthola ama-irises amabili afanayo ngu-1/1072, ngamanye amagama akunakwenzeka. Ngisho namawele afanayo anama-irises ahlukile. Lesi sici sixhashazwa yizinkampani zebhayometrikhi ezisungula izindlela zokukhomba abantu ngokubona irises zabo. Le ndlela manje isetshenziswa umhlaba wonke ngabaphathi bamasiko, emabhange noma emajele (8).

Kungani izingane zinamehlo aluhlaza okwesibhakabhaka?

Lapho kuzalwa, izingulube ze-melanin zingcwatshwa ekujuleni kwe-iris (9). Isendlalelo sayo esijulile, esinombala oluhlaza okwesibhakabhaka ngokumpunga, bese sibonakala ngokusobala.

Yingakho ezinye izingane zinamehlo aluhlaza okwesibhakabhaka. Emasontweni onke, i-melanin ingakhuphukela ebusweni be-iris futhi iguqule umbala wamehlo. Idiphozi ebusweni be-melanin izodala amehlo ansundu kanti uma ingavuki, amehlo ayohlala eluhlaza okwesibhakabhaka. Kepha lesi simo asithinti zonke izingane: iningi lezingane zase-Afrika nezase-Asia selivele linamehlo amnyama lapho zizalwa.

Amehlo aluhlaza okwesibhakabhaka, ukuvela kofuzo

Ekuqaleni, wonke amadoda ayenamehlo ansundu. Ukuguquguquka okuzenzakalelayo kofuzo kuthinte okungenani uhla olulodwa lombala wamehlo, kwavela amehlo aluhlaza okwesibhakabhaka. Ngokusho kocwaningo lwe-10 (2008), lokhu kuguquka kwavela eminyakeni engama-6000 kuya kwengu-10 edlule futhi kwavela kukhokho oyedwa. Lokhu kuguquka bekuzobe sekusakazekele kubo bonke abantu.

Ezinye izincazelo zingenzeka, kepha: lokhu kuguquka kungenzeka ukuthi kwenzeke kaningana ngokuzimela, ngaphandle kwemvelaphi eyodwa, noma okunye ukuguqulwa nakho kungadala amehlo aluhlaza okwesibhakabhaka.