In the Hirschberg corneal light reflex test, each millimeter of decentration of the corneal light reflex from the pupil centre corresponds to approximately how many prism diopters of deviation?

• A 15 prism diopters
• B 22 prism diopters
• C 2 prism diopters
• D 7 prism diopters ✓

Explanation

In the Hirschberg test, 1 mm of corneal light reflex decentration corresponds to approximately 7 prism diopters (or 7Δ) of misalignment. Common landmarks: reflex at the pupil edge (~15Δ), at the limbus (~45Δ), midway between pupil edge and limbus (~30Δ). This quick bedside test is important in pre-verbal children or patients who cannot cooperate with cover testing, though the prism cover test remains the gold standard for accurate deviation measurement.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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