During automated static perimetry (Humphrey 24-2 SITA-Standard), a patient with suspected normal tension glaucoma shows a reproducible superior arcuate scotoma respecting the horizontal meridian in the nasal hemi-field. The reliability indices show fixation losses 2/20, false positive rate 2%, false negative rate 8%. The most important feature indicating this is a true glaucomatous defect rather than artefact is:

• A High mean deviation (MD) with low foveal threshold
• B Cataract-like generalised depression affecting all points equally
• C Pattern standard deviation (PSD) elevation with no generalised depression ✓
• D Clover-leaf pattern on total deviation probability plot

Explanation

A significantly elevated pattern standard deviation (PSD) with a localised arcuate defect respecting the horizontal meridian distinguishes true glaucomatous nerve fibre layer loss from diffuse media-related depression. MD measures mean sensitivity loss and is elevated in both glaucoma and cataract; cataract produces diffuse, relatively uniform depression. A clover-leaf is a reliability artefact. The arcuate scotoma respecting the horizontal mid-line and elevated PSD with acceptable reliability indices confirm genuine glaucomatous loss.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.