On corneal topography, the inferior-superior (I-S) value is an important diagnostic parameter for keratoconus screening. An I-S value above which threshold is considered suspicious for keratoconus?
- A 2.5 D
- B 1.9 D
- C 1.4 D ✓
- D 1.0 D
Correct answer: C. 1.4 D
Explanation
An inferior-superior dioptric asymmetry greater than 1.4 A on corneal topography is considered suspicious for keratoconus. This reflects the characteristic inferior steepening seen in keratoconus. Values above 1.9 A (option B) are more definitively abnormal, but 1.4 A is the screening threshold that triggers further investigation.
Reference: Cornea: Fundamentals, Diagnosis and Management, 5th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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