Inverted Pedicled Internal Limiting Membrane Flap Attached to an Optic Disc with Autologous Blood Clot for Large Macular Holes

Purpose An inverted ILM flap might be accidentally separated from the retina or sucked away during surgery for large macular holes (MHs). This article is to determine the efficacy of a new inverted pedicled internal limiting membrane (ILM) flap attached to an optic disc with an autologous blood clot (ABC) technique for the treatment of large MHs. Methods An inverted pedicled ILM flap connected to the optic disc with ABC was used to treat 12 consecutive patients with significant macular holes (>600 m). The ILM was first peeled off around MH as a semidiameter of about 1.5 diameters of the optic disc. The superior residual ILM was used to produce a pedicled ILM flap that was connected to the optic disc and was later inverted to cover the MH. The macular hole was covered with a repositioned flap larger than 2 MH diameters in an inverted way. ABC was used to fasten the flap, followed by fluid-air exchange with air or C3F8 as tamponade. Spectral domain-optical coherence tomography (SD-OCT) and best-corrected visual acuity (BCVA) were performed at each postoperative follow-up. Results The mean aperture and base macular hole diameters were 737.9 ± 109.6 µm (range, 607–982 µm) and 1244.3 ± 227.4 µm (range, 975–1658 µm). All macular holes (100%) were closed after a single surgery without intraoperative or postoperative complications related to the ILM transposition technique. At the last postoperative visit, we found one eye with a U-shaped closure, three eyes with W-shaped closures, and eight eyes with V-shaped closures. No postoperative flap closures were noted in all cases. The preoperative mean BCVA was 1.5 ± 0.3 (range, 1.1–2.0). After a mean follow-up of 5.3 ± 4.8 (range, 3–16) months, the postoperative mean BCVA was 0.8 ± 0.2 (range, 0.6–1.1), and the difference was statistically significant (p < 0.05). Conclusion This novel technique is safe and suitable for large MHs and can be an alternative option for accidental ILM flap loss during other inverted ILM flap operations.


Introduction
Pathogenesis and classifcation of an idiopathic macular hole (IMH) were frst expounded by Gass [1], and pars plana vitrectomy (PPV) with gas tamponade was initially introduced to treat MH [2]. Later, vitrectomy combined with internal limiting membrane (ILM) peeling or an ILM fap technique was introduced consecutively to improve the macular hole's anatomical outcomes and visual recovery, especially for those larger MHs [3][4][5]. As it is known, the inverted ILM fap could provide a scafold for glial cells and stimulate glial cell proliferation, which would contribute to the hole closure [6][7][8]. Hence, the inverted ILM fap procedure gradually became the primary surgery to treat MH, signifcantly for those sufering from macular holes with large diameters (>400 µm), as was suggested by several studies. However, the traditional inverted ILM fap technique has some disadvantages, including the inverted ILM fap being easy to be displaced or sucked away by using a fute needle during the gas-liquid exchange [9][10][11][12][13][14][15].
Here, we proposed a new technique that created an inverted pedicled ILM fap attached to the optic disc for covering the MH, and autologous blood clot (ABC) was used to fasten the ILM fap. Tis new technique may be suitable for large macular holes and also a good choice for accidental ILM fap loss during other inverted ILM fap operations.

Methods
A total of 12 consecutive patients with large macular holes (>600 µm) were enrolled from April 2019 to November 2021, retrospectively. Recurrent MH was not included. Tis study was performed according to the Declaration of Helsinki and approved by the Ethics Committee of Xuzhou First People's Hospital (xyy11[2021]-XJSFX-058). Written informed consent was also obtained from all the participants. Te associated video (Supplemental Digital Content 1) shows the key steps of the technique procedure.
A standard 23-gauge pars plana vitrectomy was performed under retrobulbar anesthesia in all patients by the same surgeon (H.Y.L) using Constellation (Alcon, Forth-Worth, TX, USA) under noncontact viewing system Resight 700 (Carl Zeiss Meditec AG, Jena, Germany). In this article, all enrolled patients were combined with a grade II nuclear cataract and received cataract phacoemulsifcation and IOL implantation. A traditional core vitrectomy with posterior vitreous detachment was performed by triamcinoloneassisted visualization. If present, an epiretinal membrane was peeled after the detached vitreous gel was cleared. Te peripheral retina was inspected thoroughly with scleral depression. Laser photocoagulation was applied to these retinal tears or lattices detected during surgery. Te ILM was stained with 0.1 ml indocyanine green (ICG, 1.25 mg/ml, Eisai, Inc., Shenyang, China) for 30 seconds. Next, the ILM around the MH was peeled of in an area of 2 to 3 of the size of the optic disc, ensuring the ILM at the edge of the macular hole was removed. An inverted pedicled ILM fap from the superior residual ILM was created with the size larger than a 2 MH area and the root attached to the optic disc. Afterwards, the macular hole was covered with the fap in an inverted way. Finally, ABC was used to fasten the fap, the fuild-air exchange was performed, and C3F8 or air was chosen as tamponade ( Figure 1). Patients were instructed to remain in the prone position for about 7-14 days.
Patients were investigated at 14 days, 1 month, and 3 month, postoperatively. At each visit, patients underwent examinations including best-corrected visual acuity or BCVA (logMAR) measurement, slit-lamp examination, fundus examination by using an anterior ophthalmoscope under a slit lamp, and macular imaging with spectral domain-optical coherence tomography (SD-OCT). At each postoperative visit time, the restoration of foveal microstructure, ellipsoid zone (EZ) defects, and external limiting membrane (ELM) defects were estimated by the image of spectral domain-optic coherence tomography.
Te restoration of foveal microstructure was described as U-shape, V-shape, W-shape (irregular), fap closure, fatclosure, and fat-open. Te frst three were considered with satisfactory functional results. Flap closure needed further investigation, which will make improvement to the frst   Journal of Ophthalmology three types after several months. Te last two types were considered to be associated with poor functional results [16].

Results
All macular holes (100%) were closed after a single procedure. No intraoperative or postoperative complications related to the ILM transposition technique were noted. In all cases, we succeeded in inverting the fap from the superior retina to cover the MH, with no case spontaneously returning to the original position. No accidental ILM detachment from MH during the fuid-air exchange occurred. Te detailed characteristics of patients are summarized in Table 1.

Discussion
In this new technique, the ILM at the edge of the MH was circumferentially peeled of, and the ILM fap attached to the optic disc lifted from the superior retina was inverted to cover the MH. We considered that this technique is safe and suitable for large MHs and can be an alternative option for accidental ILM fap loss during other inverted ILM fap operations.
Since Michalewska et al. introduced the inverted internal limiting membrane fap technique in 2010 [3], several modifcations have been suggested [3,9,17]. All of these were based on the common hypothesis concerning the pathogenesis that the ILM fap provides a scafold to induce glial cell proliferation and facilitate the MH closure [7,8]. Photoreceptor cells around MH may move to the fovea on the surface of gliosis to improve visual function [9-15, 17, 18]. However, the classic ILM invert technique selects the edge of the MH as the base of the fap, which might not completely release the tangential traction by the ILM. Tus, a number of large MHs yielded with a fap closure, especially for those with a diameter >600 mm. As reported, the fap closure in the previous studies was found nearly 14%-16% within one month postoperatively, most of which became V-shaped or W-shaped closures after a few months because the macular defects below the inverted ILM fap were flled with gliosis, and a few cases were still fap closures (nearly 3%) after 12 months [6]. Of note, the fnal BCVA is lower in eyes with an early fap closure than in eyes with initial U-type, V-type, or W-type closures [19,20].
Teoretically, fewer neuroretinal abnormalities underneath the surgical ILM fap lead to more photoreceptor cells in the fovea, which could yield a better visual outcome [8]. We suspect that the postoperative fap closure could be avoided by releasing the tangential traction of ILM ( Figure 3).
A proportion of the surface of ILM around MH contains the residual posterior vitreous cortex to strengthen the tangential traction, so enough release becomes more critical. Concerned about these problems, we modifed the technique. In this new technique, the ILM around MH in an area of 2 to 3 of the size of the optic disc as semidiameter is peeled of. Te ILM fap attached to the optic disc is lifted from the superior edge of residual ILM. Our new technique combines the benefts of both ILM peeling and ILM fap covering. Tere was no "fap-closure" case in our report, which is consistent with previous reports, concerning modifying the inverted ILM fap technique along with circumferentially releasing ILM [15,21]. Moreover, the restoration of foveal microstructures was observed in this study.
Maintaining the stability of the ILM fap was the most challenging part of maneuvering, similar to other ILM fap techniques. In order to improve the retention of the ILM fap-covering MH, key procedures are as follows: First, the ILM fap should be attached to the optic disc, and tight adhesion ensures no free ILM fap. Second, the ILM fap position is transferred from the superior to cover MH, thus avoiding position change because of gravity when the head is upright. Tird, ABC was used to fasten the fap. Te fresh ABC soon became a clot to cover the macular area after being injected to cover the fap before the fuid-air exchange [22]. Besides, the blood clot is cost-efective, readily available from the patient's antecubital vein, and has extra growth factors to promote MH healing. By applying the abovementioned methods to 12 patients enrolled in this study, our results did not reveal any ILM fap displacement during the fuid-air exchange, proving the efectiveness of the abovementioned methods. In addition, this new technique can be a remedy for accidental ILM fap loss during other inverted ILM fap operations. Sometimes, this is an optional method to treat recurrent MH, with no ILM around MH.
In conclusion, this new surgical technique is safe and efective in treating large macular holes. Te advantages of this technique include enough relief of tangential traction around MH and the transposition of the superior pedicled ILM fap to facilitate the MH closure. Long-term follow-up of more patients is needed to confrm the advantage of this technique. Comparable studies are also needed to confrm the superiority of these modifcations over the classic inverted ILM fap technique.

Data Availability
Te datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Ethical Approval
Tis study was performed following the guidelines of the Declaration of Helsinki and approved by the Ethics Committee of Xuzhou First People's Hospital.

Consent
Written informed consent was obtained from all study participants.

Disclosure
Te funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Lishuai Zhang and Huiyu Xi are the co-frst authors.

Conflicts of Interest
Te authors declare that they have no conficts of interest.