A 38-year-old woman reports bumping into door frames on both sides for several months. Visual acuity is 6/6 in each eye. Perimetry shows a complete bitemporal hemianopia. The most likely site of the lesion is:
- A Body of the optic chiasm ✓
- B Left optic tract
- C Right lateral geniculate body
- D Anterior calcarine cortex
Correct answer: A. Body of the optic chiasm
Explanation
Crossed nasal retinal fibres decussate in the body of the chiasm and carry the temporal visual fields of both eyes, so a central chiasmal lesion produces bitemporal hemianopia. A pituitary macroadenoma compressing the chiasm from below is the commonest cause in this age group. An optic tract lesion gives a contralateral incongruous homonymous hemianopia, while a lateral geniculate or calcarine lesion never splits the field down the midline in both eyes.
Reference: Parsons' Diseases of the Eye, 23rd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.