Objective To compare and observe the efficacy and safety of pars plana vitrectomy (PPV) combined with 41G ultrafine needle injection of balanced salt solution (BSS) and internal limiting membrane inversion and coverage in the treatment of large-diameter macular hole (MH). MethodsA prospective study. From April 2023 to April 2024, 42 patients (42 eyes) diagnosed with large-diameter MH at The Affiliated Eye Hospital of Nanchang University were included in the study. The substrate diameters (BD) of MH are all greater than 1 000 μm. All affected eyes underwent best corrected visual acuity (BCVA), microvisual field, optical coherence tomography (OCT), and OCT angiography (OCTA) examinations before surgery. BCVA examination was conducted using the international standard logarithmic visual acuity chart, and the statistics were converted to the logarithm of the minimum angle of resolution (logMAR) visual acuity. Microfield-of-view examination records the mean retinal sensitivity (MS) within a 12° range of the fovea. The minimum diameter (MD) and BD of the hole were measured by OCT and the MH index (MHI) was calculated. OCTA measures the area and perimeter (PERIM) of the foveal avascular zone (FAZ) in the fovea centralis, as well as the retinal vessel length density (VLD) and vessel perfusion density (VPD) in the central area. The affected eyes were divided into the observation group (22 eyes, treated with PPV combined with 41G ultra-micro needle subretinal injection of BSS and the control group (20 eyes, treated with PPV combined with internal limiting membrane inversion and coverage) according to the random number table method. The patients were followed up for 6 months after the operation, and the above indicators were reexamined at 1, 3 and 6 months. The changes of BCVA, MS, FAZ parameters, VLD, VPD before and after the operation, as well as the closure of the hole and the occurrence of complications were compared between the two groups. The independent sample t test was used for comparison between groups. The correlation between postoperative indicators and preoperative structural parameters was analyzed using Pearson analysis. ResultsIn the 22 eyes of the observation group, the hole closure rate was 100.0% (22/22) 6 months after the operation, and the complete closure rate was 90.9% (20/22). In the control group of 20 eyes, the closure rate was 95.0% (19/20), and the complete closure rate was 90.0% (18/20). The hole closure rate of the affected eyes in the observation group was better than that in the control group, but the difference was not statistically significant (χ2=1.736, P=0.420). logMAR BCVA, MS, FAZ area, PERIM, VLD and VPD at each time point after the operation in both groups were significantly improved compared with those before the operation, and the differences were statistically significant (P＜0.05). The results of Pearson correlation analysis showed that in the observation group, logMAR BCVA at 6 months after surgery was positively correlated with BD before surgery (r=0.340, P=0.029), and negatively correlated with MHI before surgery (r=−0.350, P=0.023). Six months after the operation, MS was positively correlated with the preoperative hole height and MHI (r=0.330, P=0.034). In the control group, 6 months after the operation, MS was negatively correlated with BD before the operation (r=−0.480, P=0.032), and positively correlated with MHI before the operation (r=0.510, P=0.027). Six months after the operation, the FAZ area of the affected eyes in the observation group [(0.17±0.09) mm2] was larger than that in the control group [(0.12±0.07) mm2], and the difference was statistically significant (t=−0.340, P=0.025). No complications such as abnormal intraocular pressure, retinal pigment epithelium injury or retinal detachment occurred in all the affected eyes after the surgery. ConclusionsPPV combined with 41G ultra-micro needle subretinal injection of BSS for the treatment of large-diameter MH has a high rate of hole closure and good safety. Larger BD and MD, lower MHI and hole height before surgery may affect the recovery of visual function after surgery.