AIM:To investigate the efficacy and safety of pars plana vitrectomy(PPV)combined with inverted internal limiting membrane(ILM)flap and PPV combined with ILM tamping in the treatment of large basal diameter idiopathic macular hole(IMH), and to analyze the correlation between postoperative visual acuity and preoperative parameters.

METHODS:This study is a retrospective clinical study. Totally 56 patients(57 eyes)with macular hole bottom diameter greater than 1 000μm, who treated in Joint Shantou International Eye Center from January 2018 to December 2020, were enrolled in this study. Thirty eyes were involved in PPV combined with inverted ILM flap(Group 1)and 27 eyes were involved in PPV combined with ILM tamping(Group 2). The best corrected visual acuity(BCVA), the closure of the macular hole, thickness of foveal neurosensory layer and complications were compared between the two groups at 1wk and 1mo after the surgery. Person correlation analysis was used to explore the correlation between preoperative parameters and BCVA at 1mo after operation.

RESULTS: There was no significant difference in gender, age, eye type, course of disease, preoperative BCVA, postoperative macular hole healing classification, preoperative hole bottom diameter and eye axis between the two groups(P>0.05). The closure rate of macular hole in Group 1 was 97%, of which type 1 closure was 80%. The closure rate of macular hole in Group 2 was 100%, of which type 1 closure was 78%, and there was no significant difference in the closure rate(P=0.99). The postoperative follow-up BCVA of patients in both groups was better than that before operation(all P<0.01). The BCVA of Group 1 was better than Group 2 at 1mo after operation, and the difference was statistically significant(t= -2.20, P=0.03). There was no significant difference in the thickness of foveal neurosensory layer between two groups at 1mo after operation(t=0.407, P=0.69). The BCVA at 1mo after operation was positively correlated with the hole diameter and preoperative BCVA(r=0.435, P=0.004; r=0.440, P=0.001). There was no complication in both groups during and after operation.

CONCLUSION:PPV combined with inverted ILM flap and PPV combined with ILM tamping can improve the closure rate of the hole. The long-term visual acuity of PPV combined with inverted ILM flap is better than that of PPV combined with ILM tamping. There is a significant positive correlation between postoperative BCVA and the bottom diameter of the hole and preoperative BCVA. Preoperative bottom diameter can be used as one of the basis for clinical prognosis.