Correlation of Visual Field Loss with MRI Findings in Patients with Pituitary Tumours

The exact mechanism which gives rise to bitemporal hemianopia in chiasmal compression by pituitary tumors is currently unknown. One theory suggests that it is simply the fact that crossing fibres cross each other, resulting in less surface area of contact and, in turn, greater stress from compressive forces than are experienced by uncrossed fibres. Finite element modelling has been used to investigate this in silico but the hypothesis needs testing in vivo. This study aimed to determine whether extrinsic chiasmal compression was associated with patterns of visual field loss which supported the ‘crossing hypothesis' or predictions based on the anatomy.