A patient with a pituitary tumor would exhibit which of the following disorders (AIIMS May 2007)
|A||Bitemporal (heteronymous) hemianopia|
|B||Right nasal hemianopia|
|C||Left homonymous hemianopia|
Bitemporal (heteronymous) hemianopia
• The optic chiasma is the part of the brain where the optic nerves partially cross.
• Specifically, the nerves connected to the right eye that attend to the right temporal visual field cross towards the left side to enter the left optic tract. The left optic tract, which already was carrying the left nasal visual field.
• Hence, the fibres carrying nasal visual field go ipsilaterally, whereas, the temporal visual fields become contralateral by a cross-over at optic chiasma.
• It also concluded that the parts of both eyes that attend to the right half of visual field are processed in the left visual system (cortex) in the brain, and vice versa.
• So, a lesion at the optic chiasma is basically damages the temporal visual field fibres of both the eyes, and thus produce a bitemporalhemianopsia, leading to tunnel vision (loss of peripheral vision in both eyes)