Quantifying surgical skill in macular surgery

PURPOSE: To evaluate the relationship between patient outcome and surgical experience by developing an objective quality measure of macular hole surgery based on forceps damage to the inner retina.

METHODS: We retrospectively examined 3 macular hole case series >1 year after pars plana vitrectomy, internal limiting membrane peeling and gas tamponade. The patients were operated by (1) a novice surgeon (<20 cases), (2) an intermediate (150+ cases) and (3) an experienced surgeon (2000+ cases). Primary outcome was inner retinal volume defect as segmented from optical coherence tomography (GCL++: thickness from internal limiting membrane to inner plexiform layer). Secondary outcome was retinal function measured by confocal microperimetry using a custom scanning protocol.

RESULTS: Thirty-two patients were examined: 11, 10 and 11 patients in the novice, intermediate and experienced surgeon group, respectively. Median GCL++ volume defect was 23.68 × 106 μm3 (IQR: 22.77 × 106 -44.81 × 106 μm3 ), 8.42 × 106 μm3 (IQR: 4.86 × 106 -10.03 × 106 μm3 ) and 3.55 × 106 μm3 (IQR: 1.44 × 103 -7.94 × 106 μm3 ) in the novice, intermediate and experienced surgeon group, respectively (p = 0.0004). The novice surgeon volume defect differed significantly from the intermediate and experienced surgeon (p = 0.016 and p = 0.0002, respectively). A subset of 12 patients underwent microperimetry measurements demonstrating correlation between inner retinal volume defect and reduced retinal sensitivity (p = 0.02).

CONCLUSIONS: Forceps induced inner retinal damage commonly occurs during initiation of internal limiting membrane peeling in macular hole surgery. Damage to the structure and function of the inner retina seems to correlate to surgical experience.