This study examined the effects of preserving foveal flaps on the functional and anatomical prognosis of MH surgery and introduced a technique for preserving such flaps during surgery. To this end, a control group was selected, in which the opercula were clearly visible in the posterior vitreous plane on preoperative SD-OCT scans. We believe that our control group is able to represent the following situations: 1) spontaneous PVD progressed and the foveal flap was lost into the operculum; 2) the iatrogenic operculum formed in the process of PVD induction during macular hole surgery for MH with foveal flap. Neither the MH size nor preoperative visual acuity, which are known to have significant effects on the prognosis of MH surgery,24–26 showed any significant differences between the two groups. The group in which flaps were preserved showed better functional and anatomical results after surgery than the group in which opercula were present. Functionally, the study group exhibited a statistically significant improvement in the postoperative BCVA compared with the control group, and anatomically, the study group showed a tendency toward better and faster, although not statistically significant, restoration of the microstructure of the foveal photoreceptor, namely, ELM and EZ, which is known to be related to a good postoperative prognosis of vision on SD-OCT scans.27–29 In both groups, restoration of the foveal microstructure was observed within 12 months after surgery. In other words, if complete restoration fails within 12 months of surgery, it can be assumed that restoration is difficult to achieve. Therefore, the 12-month follow-up criterion in this study is considered to be clinically valid. This result suggests that even MH of the same size and stage may have different prognosis according to the status of the operculum and the foveal flap. In addition, preservation of the flap without forming an iatrogenic operculum during surgery may have a significant impact on prognosis.
To facilitate the closure of MHs, various surgical techniques have recently been proposed.30–34 One such example is the inverted ILM flap technique, in which instead of completely removing ILM, MH is covered with an inverted ILM flap to facilitate the healing process.30–32 Through this technique, it is assumed that the inverted ILM facilitates gliosis and functions as a scaffold for tissue proliferation, assisting in the closure of MHs. If the ILM can help in the closure of MHs, we can assume that preserving foveal flaps, which are believed to include more retinal tissues such as Muller cells and cone photoreceptors, and using them to cover the sites of MHs may have important implications in prognosis after MH surgery. Because the preserved foveal flaps can more quickly cover-up defects in the inner retina and function as a scaffold for tissue proliferation, they are believed to be helpful in the faster closure of MHs. During this study, OCT scans of the 9 eyes in the study group were obtained on Day 1 after surgery. Although it was unclear owing to the filled gas, OCT images appeared to show complete restoration of the inner retina integrity. When examining OCT images taken between 1 week and 1 month after the procedure; a tissue with a signal intensity distinct from the surroundings, which seemed to be the saved flap, was found covering the top of the fovea and was observed as a shape linking both sides of the retinal tissue as a bridge (Figure 3). The fast closure of MHs might produce an environment for the photoreceptors to assume new positions in direct proximity to the fovea. Furthermore, it is believed that if some cone photoreceptors considered to remain in the study group are preserved, they can also be helpful for the prognosis of vision. Therefore, this study concludes that in cases with a greater size or amount of foveal flaps, the preservation of flaps may have a greater significance. Future studies should be conducted on methods for quantitatively measuring flap sizes and effects of their preservation on prognosis. In addition, combining the inverted ILM flap technique and preserving the flap might help in obtaining the best anatomical and functional outcomes in case of a large MH with a flap.
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. And selection bias may have occurred while recruiting the control group. Therefore, prospective comparative studies with a larger cohort of patients will be necessary to assess the importance of preserving the foveal flap. Although preservation of the flap could be identified by the surgeon under the microscope during the procedure, the use of intraoperative OCT in the future may be helpful for making more objective assessments during the entire operation.
In conclusion, preservation of the flap might improve both the functional and anatomical outcomes of vitrectomy for Stage 2 or 3 MHs with foveal flap. Therefore, to improve the prognosis in cases of MHs that present with a foveal flap on OCT scans and are associated with anteroposterior traction arising from perifoveal PVD, we could consider early surgery before the flap becomes detached as an operculum along with PVD. In this hospital, we are attempting to perform the operation for MH with a flap as soon as possible. There had been no case in which the flap was lost as operculum when the operation was performed within 1 to 2 weeks of the diagnosis. The progression from flap to operculum might be affected by several factors, and additional studies on the optimal time of operation will be needed. Also, the saved foveal flap technique was useful for avoiding the formation of iatrogenic operculum during surgery.
Our conclusion suggests that the prevention of additional foveal tissue defects is one of the important factors for achieving the best anatomical and functional outcomes after MH repair.
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