In gonioscopy of a suspected angle-closure patient, the clinician uses the Shaffer grading system. A grade 2 angle is described as:
- A Wide open angle; all structures visible including ciliary body band
- B Very narrow angle; only Schwalbe's line visible; closure very likely
- C Narrow angle where the posterior trabecular meshwork can barely be seen; closure possible ✓
- D Angle closed; no trabecular meshwork visible
Correct answer: C. Narrow angle where the posterior trabecular meshwork can barely be seen; closure possible
Explanation
The Shaffer grading system grades the angle from 4 (wide open, 35–45°) to 0 (completely closed). Grade 2 represents a 20° angle where the posterior trabecular meshwork can just be seen; angle closure is considered possible. Grade 1 (10°) means only the anterior trabecular meshwork/Schwalbe's line is visible and closure is probable. Grade 0 is complete apposition. Grades ≤2 warrant prophylactic laser peripheral iridotomy if the fellow eye has already had angle-closure.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
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Written and medically reviewed by the StethoPrep medical team.