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What is the Thinnest part of neuro-retinal rim according to ISNT rule ?
What is the Thinnest part of neuro-retinal rim according to ISNT rule ?
Updated On: Jun 23, 2026
- Inferior
- Superficial
- Temporal
- Medial
Show Solution
The Correct Option is C
Solution and Explanation
Step 1: Spell out the mnemonic. ISNT stands for Inferior, Superior, Nasal, Temporal, listed in decreasing rim thickness. A healthy optic disc obeys this sequence on examination.
Step 2: Pull the answer from the last letter. Since the order runs thickest to thinnest, the final quadrant - Temporal - is by definition the thinnest part of the neuro-retinal rim in a normal eye.
Step 3: Discard the rest. Inferior is the thickest, the exact opposite of what is asked. "Superficial" and "medial" are not even members of the ISNT scheme. Note that violation of the ISNT rule, particularly inferior or superior notching, is an early sign of glaucomatous damage.
\[\boxed{\text{Temporal}}\]
Step 2: Pull the answer from the last letter. Since the order runs thickest to thinnest, the final quadrant - Temporal - is by definition the thinnest part of the neuro-retinal rim in a normal eye.
Step 3: Discard the rest. Inferior is the thickest, the exact opposite of what is asked. "Superficial" and "medial" are not even members of the ISNT scheme. Note that violation of the ISNT rule, particularly inferior or superior notching, is an early sign of glaucomatous damage.
\[\boxed{\text{Temporal}}\]
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