I-Chiasma Opticum (ephinde ibizwe ngokuthi i-Optic Chiasm noma i-Optic Commisure) isakhiwo esisengqondweni lapho izinzwa ze-optic ezivela esweni ngalinye ziwelana. Lokhu kubangela ukuthi inkambu yokubukwa yesokunxele icutshungulwe uhlangothi lwesokudla lobuchopho kanye nendawo yokubuka engakwesokudla icutshungulwe uhlangothi lwesobunxele lobuchopho. Igama elithi "Chiasma Opticum" lisuselwa egameni lesiLatini elithi "chiasma", elisho "ukuwela", kanye "opticum", okusho ukuthi "optical".