Several authors have recently shown MH geometry changes on iOCT after ILM peeling in MH surgery14.However, the relationship of these intraoperative changes with the MH closure rate and anatomic normalization were less analyzed.Our study found that there were three types of iOCT features at the hole edge observed after ILM peeling. The morphological characteristics of iOCT are closely related to the prognosis of MH surgery, in that foveal flap and Hole-door changes in iOCT during surgery served as a positive predictor of MHs that acquired better functional and anatomic results after surgery than the group in which these features were present.
Though the nature of the foveal flap is still unknown, it is considered to be the early stage of operculum16, 17. As PVD progresses, the foveal flap is separated from the retinal tissue and detached in the form of an operculum.Histopathological observation of the operculum shows the presence of retinal tissue18, 19, implying that the fovea flap is a part of the retinal tissue which distraction by posterior vitreous cortex.There was a report regarding preserving the foveal flap for the treatment of MH,in which good functional and anatomic outcomes were achieved 20.Although preservation of the flap could be identified by the surgeon under the microscope during the procedure, the use of iOCT may be helpful for making more objective assessments during surgery. Our study observed the morphology of the foveal flap after ILM removal using iOCT, and found that all flaps were preserved as confirmed by iOCT during the surgery,and these patients all had a better prognosis. We assumed that the preserved foveal flaps may be helpful in the faster closure of MHs via more quickly covering up defects in the inner retina and functioning as a scaffold for tissue proliferation, also produce an environment for the photoreceptors to be restored at the fovea. To the best of our knowledge, this study is the first to use iOCT to describe the feature of fovea flap after ILM peeling and to demonstrate its beneficial effect for prognosis after MH surgery.
However, in the patients who did not have fovea flap,iOCT also showed vertical pillars of tissue at the edges of the hole projecting into the vitreous cavity after ILM peeling in eight patients.This phenomenon is similar to the “hole-door” feature described in previous literature21,they conclude Hole-door sign can predicts postoperative Type–1 closure of MH. In Our study,we found that patients with this phenomenon have a better recovery of the foveal microstructural and visual outcome compared with the negative group,while there is no difference in the closure rate of MH. The different mean diameter of holes in selected cases may be the main reason, an average of 420um in our study, while 501um in their study. These tissue pillars may be composed of redundant retinal tissue, subclinical epiretinal membranes, or small residual pieces of ILM attached to the edges of the hole. The mechanism may be similar to the invert ILM flap technology22, providing mechanical support to bridge the gap,more quickly cover up defects in the inner retina; Moreover, they are believed to be helpful in the faster closure of MHs and recovery of the photoreceptors.
Visual recovery after MH closure may depend on the microstructural recovery of the fovea, particularly the outer retina5–8. A restoration of the outer nuclear layer (ONL) with recovery of the ELM and the EZ lines over the closed MH was associated with better BCVAs in 50% of the eyes. By contrast, a lack of restoration of the ONL but with the hyper reflective bridging tissue at the closed MH indicated that the MH was closed with scarred tissue or migrated glial tissue including collagen components derived from Müller cells. The restoration of the ELM in the foveal flap group and the hole-door group was higher than in the negative group, and correspondingly, the foveal flap and hole-door groups had better visual acuity. Our research proves favorable visual outcomes after MH surgery related to restoration of the ELM, and this is similar to previous reports.This observation indicated that the recovery of the ELM might be the most critical component for visual function improvement in the early stage after MH surgery.
The size of the hole is closely related to the prognosis,and a study showed that patients with smaller MHs had superior final visual acuity and better restoration of the outer retinal structure after MH surgery23. Although the current management options for small or medium MHs have been reviewed extensively, treatment options for large, recurrent, or persistent MHs have yet to come to a general consensus because of the lack of randomized clinical trials with sufficiently large sample sizes. Regarding preoperative MH size, Liu L et al stated that simply dividing patients into a larger than 400 μm group or400 μm or less group might be more clinically significant for the purpose of preoperative counseling of patients about prognosis after MHs surgery8. This study shows that the intraoperative feature at the hole edge may be the predictor of prognosis of MH in MHD greater than 400μm. Inverted ILM flap technique has been widely used in the treatment of refractory macular hole, including large macular hole. These phenomenons found by iOCT may be similar to the iverted ILM flap,which is assumed that the facilitates gliosis and functions as a scaffold for tissue proliferation, assisting in the closure of MHs and restoration of outer retinal structure.
This study has the following limitations. It was a retrospective study and involved a small number of cases,, which limited the statistical strength of the analysis. In addition, the imaging system used in this study was not integrated into the microscope, which may impact the overall functionality of iOCT in these cases.
Both research systems and commercial systems have been described that provide microscope-integrated technology. A number of studies of microscope-integrated iOCT systems have provided early data suggesting the feasibility and potentially significant usefulness of this technology. The 3-year results of the DISCOVER study found that posterior segment surgeons seemed to prefer static imaging over time in the subsequent years of the study. In 69% of procedures, posterior segment surgeons preferred viewing images on the display screen as well, which increased from year 1 to subsequent years. These improvements may be related to greater OCT detail and subtle changes on the OCT required in on-screen review than in real-time OCT. Therefore, non-microscope-integrated iOCT can be used for static image analysis, and it is still of important clinical value in guiding the treatment of MH.