This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Ophthalmology
Bitemporal hemianopia is due to lesion of : 
Select and explain. 
A. Optic chiasma, B. Optic tract, C. Optic radiation, D. Optic nerve
A: Optic chiasma
Answer: A: Optic chiasma 
Explanation: A chiasmatic lesion (often owing to a pituitary tumor or a lesion around the sella turcica) can injure the decussating axons of retinal ganglion cells within the optic chiasm. These axons originate in the nasal halves of the two retinas. Thus, this type of lesion produces bitemporal hemianopsia, characterized by blindness in the lateral or temporal half of the visual field for each eye. Ref : Waxman S.G. (2010). Chapter 15. The Visual System. In S.G. Waxman (Ed),Clinical Neuroanatomy, 26e.