Vision test, iyo Ishihara bvunzo inonyanya kufarira maonero emavara. Nhasi ndiyo bvunzo inonyanya kushandiswa pasi rese kuongorora marudzi akasiyana ehupofu hwemavara.

Inofungidzirwa muna 1917 napurofesa weJapan Shinobu Ishihara (1879-1963), bvunzo yeIshihara inzvero yechromatic yekuongorora maonero emavara. Zvinoita kuti zvikwanise kuona kumwe kutadza kunoenderana nekuona kwemavara (dyschromatopsia) kunowanzo kuunganidzwa pasi peizwi rekuti color blindness.

Muedzo unoumbwa nemapuranga makumi matatu nemasere, akaumbwa nemosaic yemadota emavara akasiyana, umo chimiro kana nhamba inoonekwa nekuda kwechikamu chemavara. Naizvozvo murwere anoedzwa pakukwanisa kwake kuziva chimiro ichi: bofu reruvara harigoni kusiyanisa mufananidzo wacho nokuti haaoni ruvara rwawo zvakarurama. Muedzo wakakamurwa kuita akasiyana akateedzana, imwe neimwe yakanangidzirwa kune chaiyo anomaly.

Muedzo unoitwa muhofisi yeophthalmology. Murwere anofanira kupfeka magirazi ake ekugadzirisa kana achida. Maziso ese ari maviri anowanzo kuedzwa panguva imwe chete.

Mahwendefa acho anoratidzwa mumwe mushure memumwe kumurwere, uyo anofanira kuratidza nhamba kana chimiro chaanosiyanisa, kana kusavapo kwechimiro kana kuti nhamba.

Muedzo weIshihara unopiwa kana paine fungidziro yekupofomara kwemavara, semuenzaniso mumhuri dzemapofu eruvara (iyo inosarudzika kazhinji ine geneti) kana panguva yekuongororwa kwemaitiro, semuenzaniso pamusuwo wechikoro.

Mhedzisiro yebvunzo inobatsira kuongorora marudzi akasiyana ehupofu hwemavara:

• protanopia (munhu haaoni tsvuku) kana protanomaly: maonero ekutsvuka anoderedzwa
• deuteranopia (munhu haaoni girinhi) kana deuteranomaly (maonero egirinhi akaderedzwa).

Sezvo bvunzo iri qualitative uye kwete uwandu, hazviiti kuti zvikwanise kuona pamwero kurwisa munhu, uye saka kusiyanisa deuteranopia kubva deuteranomaly, somuenzaniso. Kuongorora kwakadzama kweophthalmologic kuchaita kuti zvikwanise kutsanangura rudzi rwehupofu hwemavara.

Muedzo zvakare haugone kuongorora tritanopia (munhu haaone mavanga uye tritanomaly (kuderera kwekuona kwebhuruu), izvo zvisingawanzo.

Hapana kurapa ikozvino kunoita kuti zvibvirire kuderedza upofu hwemavara, izvo zvakare hazvikonzeri hurema hwezuva nezuva, uye hazvishandure kunaka kwekuona.