Question

A 33 year old female patient presented with inability to see the right side from both the eyes. What is the most probable cause?

• A. Injury to Left Optic Tract
• B. Right occipital lobe lesion
• C. Optic chiasma lesion
• D. Right optic nerve lesion

Hint:

Think about which side of the brain processes the right visual field.

Answer 1

The Correct Option is A

Step 1: Identify the visual field defect.
The patient cannot see the right side from both eyes. This is called right homonymous hemianopia -- loss of the right visual field in both eyes simultaneously.

Step 2: Trace the visual pathway.
The visual pathway runs as follows: each retina sends fibres via the optic nerve to the optic chiasma. At the chiasma, nasal fibres cross to the opposite side while temporal fibres remain ipsilateral. After the chiasma, fibres travel in the optic tract to the lateral geniculate body and then to the occipital cortex.

Step 3: Localise the lesion.
Right homonymous hemianopia means the right visual field is lost in both eyes. The right visual field is processed by the left optic tract (and beyond). A lesion of the left optic tract interrupts fibres carrying the right visual field from both eyes, producing right homonymous hemianopia. A right occipital lobe lesion would cause left homonymous hemianopia (or left homonymous hemianopia with macular sparing). An optic chiasma lesion causes bitemporal hemianopia. A right optic nerve lesion causes total visual loss in the right eye only.

Conclusion: The correct answer is Injury to Left Optic Tract.