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 seen in the lesion of: March 2009 
Select and explain. 
A. Lateral geniculate body, B. Optic nerve, C. Optic chiasma, D. Optic tract
C: Optic chiasma
Answer: C: Optic chiasma 
Explanation: Ans. C: Optic chiasma Bilateral/Bitemporal hemianopia is a loss of temporal field vision in both eyes. This may be caused by a lesion that affects the centre of the optic chiasm and damages fibres from the nasal halves of the retina as they decussate. It is usually caused by the tumours in the region of sella turcica, pressure by a suprasellar aneurysm or by chronic arachnoiditis Possible causes of this condition include: Pituitary tumour Craniopharyngioma Suprasellar meningioma