Investigation of the effects of idiopathic macular hole surgery on retinal layers and microvascular structures using optical coherence tomography

Introduction and Aim: Idiopathic macular hole (MH) is a vertical full-thickness defect of the foveal neurosensory retina. Its treatment is surgical, aiming at anatomical closure of the macular hole and functional improvement in visual acuity. The nourishment of the posterior segment is provided by retinal and choroidal vessels. Surgical intervention induces various changes in the posterior segment structures. This study aims to investigate the effects of macular hole surgery on retinal and choriocapillaris layers as well as microvascular structures using optical coherence tomography angiography (OCTA). Materials and Methods: This study included 35 eyes of 35 patients who underwent surgery for MH at the Retina Clinic of Manisa Celal Bayar University Hafsa Sultan Hospital. Postoperative measurements were performed at 6-24 months using 6x6 mm macular sections. Parameters such as vascular densities (VD) of the superficial capillary plexus (SCP) and deep capillary plexus (DCP), macular thickness, foveal avascular zone (FAZ) parameters, subfoveal choroidal thickness (SFCT), choriocapillaris flow areas, and outer retinal flow areas were evaluated using OCTA. The measurements were compared with the patients' fellow eyes and a control group. Results: Among the participants, 22 underwent pars plana vitrectomy (PPV) with internal limiting membrane (ILM) peeling and gas tamponade, while 13 underwent PPV with temporal ILM flap and gas tamponade. Operated eyes were compared with fellow and control eyes. Additionally, two subgroups were formed based on ILM excision and ILM flap techniques. The mean age of the patients was 65.23 ± 5.83 years (range: 51-79). Of the patients, 22 (62.9%) were female, and 13 (37.1%) were male. Postoperative best-corrected visual acuity (BCVA) showed a significant improvement compared to preoperative values (p<0.001). Significant improvements in BCVA were also observed within both the ILM excision (p<0.001) and ILM flap groups (p=0.004). Comparing operated eyes with fellow eyes, significant differences were observed in foveal and perifoveal SCP VD (p<0.001 and p=0.008, respectively), while there was no significant difference in whole-image or parafoveal SCP VD. A significant difference in foveal DCP VD was noted between operated and fellow eyes (p<0.001). FAZ area also demonstrated a significant difference between the groups (p<0.001), while SFCT and SFCT measurements showed no statistically significant differences. When operated eyes were compared with the control group, all SCP and DCP VD values were significantly lower in operated eyes (p<0.001). SFCT and choriocapillaris flow areas were also significantly reduced compared to the control group (p<0.001 and p=0.036, respectively). In subgroup analysis, SFCT was significantly lower in the ILM flap group compared to the ILM excision group (p=0.048). The only significant difference between single-operation eyes and reoperated eyes was found in parafoveal DCP VD (p=0.013). Preoperative BCVA showed a moderate negative correlation with whole-image SCP VD (r=-0.392, p=0.02) and perifoveal SCP VD (r=-0.388, p=0.021). Conclusion: Postoperative OCTA findings demonstrate a significant reduction in FAZ area and SCP VD compared to fellow eyes. When compared to the control group, both SCP and DCP showed notable decreases in vascular densities. Postoperative BCVA values negatively correlated with SFCT and choriocapillaris flow areas. Larger sample sizes and longer follow-up studies are needed to elucidate the impact of macular hole surgery on microvascular structures and their relationship with visual outcomes. Keywords: Macular hole, optical coherence tomography angiography, superficial capillary plexus, deep capillary plexus, foveal avascular zone, choroidal blood flow.