Retinal nerve fibre layer (RNFL) thinning on OCT in glaucoma characteristically occurs FIRST in which sector of the optic nerve head?
- A Inferior sector ✓
- B Superior sector
- C Temporal sector
- D Nasal sector
Correct answer: A. Inferior sector
Explanation
OCT RNFL analysis (using a 3.46 mm diameter circle scan around the optic nerve) typically shows earliest RNFL thinning in the inferior sector in POAG, corresponding to superior arcuate visual field defects. The inferior RNFL (5–7 o'clock sector) has larger axon bundles and less redundancy, making it more vulnerable to early glaucomatous loss. The ISNT rule (normal: Inferior > Superior > Nasal > Temporal thickness) is violated earliest in the inferior quadrant.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.