A 42-year-old Asian woman presents with IOP of 32 mmHg on Goldmann applanation tonometry. Gonioscopy reveals Shaffer grade 1 angle bilaterally with trabecular meshwork not visible. Pachymetry shows central corneal thickness (CCT) of 510 μm OU. The Shaffer grade 1 angle corresponds to which degree of angle opening?
- A 10 degrees — extremely narrow, closure possible ✓
- B 0 degrees — closed angle with apposition
- C 20 degrees — moderately narrow, closure possible
- D 30 degrees — moderately wide, unlikely to close
Correct answer: A. 10 degrees — extremely narrow, closure possible
Explanation
The Shaffer grading system classifies the anterior chamber angle by the angle between the iris and trabecular surface: Grade 4 = 35–45°, wide open; Grade 3 = 25–35°, open; Grade 2 = 20°, moderately narrow (closure unlikely); Grade 1 = 10°, very narrow (closure possible); Grade 0 = 0° closed (iridocorneal contact). Grade 1 at 10 degrees represents a very narrow angle where complete closure is possible with mydriasis or other provocative factors. Trabecular meshwork is not visible with Grade 1, confirming the clinical description.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.