A patient presents with bilateral temporal hemianopia. MRI shows a pituitary macroadenoma compressing the optic chiasm. The decussating fibres at the chiasm carry which visual field information?

• A Nasal retinal fibres carrying temporal visual field information ✓
• B Temporal retinal fibres carrying nasal visual field information
• C Macular fibres from both eyes which remain ipsilateral
• D Superior retinal fibres only from both eyes

Explanation

At the optic chiasm, nasal retinal nerve fibres (which carry temporal visual field information) decussate to the contralateral optic tract. Temporal retinal fibres (carrying nasal visual field information) remain ipsilateral. A central chiasmal compression damages the crossing nasal fibres from both eyes, causing bitemporal hemianopia (loss of both temporal fields). The macular fibres cross posteriorly in the chiasm and their selective preservation explains the phenomenon of 'macular sparing' in some chiasmal lesions.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.