In Humphrey visual field testing, a patient with early glaucoma shows a 'rectangular scotoma' respecting the horizontal meridian and not crossing it. This pattern localizes the defect to which anatomical structure?

• A Macular photoreceptors
• B Occipital cortex
• C Lateral geniculate nucleus
• D Optic disc (retinal nerve fiber layer) ✓

Explanation

Retinal nerve fiber layer fibers arcuate around the macula and respect the horizontal raphe. Glaucomatous damage produces scotomas that respect the horizontal meridian (nasal step, arcuate scotoma). Post-chiasmal lesions respect the vertical meridian; cortical lesions show macular sparing and congruity.

Reference: Walsh and Hoyt's Clinical Neuro-Ophthalmology, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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