Commentary: Inverted internal limiting membrane flap for large macular holes: Evaluation of new surgical techniques need new macular hole closure classification systems.

The treatment of full-thickness macular hole (FTMH) underwent its first revolution in 1991 after Kelly and Wendel started performing vitrectomy for these patients.[1] There have been immense technological refinements in the surgical technique and instrumentation since then. After the introduction of internal limiting membrane (ILM) peeling, the anatomical success rates have reached as high as 93%–98%.[2] Many preoperative optical coherence tomography (OCT) factors were devised to predict the outcome of the surgery, such as base diameter (BD), minimum diameter (MD), height, hole forming factor, macular hole index, diameter hole index, tractional hole index, macular hole angle, predicted length devoid of photoreceptors, extent of ellipsoid zone, and external limiting membrane defect.[3] It has been found that the success rate is lower for large MHs. The International Vitreomacular Traction Study has classified MH into small (<250 microns), medium, (250–400 microns) and large (>400 microns) based on the MD. However, with the improvement in surgical results, it has been proposed that the term “large” MH should be reserved for MD >650 microns in size.[4]

The next revolution came after Michalewska et al.[5] described the inverted ILM flap technique (IFT) for the treatment of large MHs (MD >600 microns). Several authors have reported that the technique helps achieve higher anatomical success compared to the ILM peeling alone. The IFT has undergone numerous modifications such as temporal-only flap, single-layered flap, semi-circular flap, cabbage-leaf technique, and the use of viscoelastic and perfluorocarbon liquid to prevent flap dislocation. Other tissues used to stuff the hole include the anterior or posterior lens capsule, autologous retinal flap, and human amniotic membrane.[6] However, none of the earlier studies have evaluated the role of the preoperative macular hole OCT factors in predicting the anatomical outcome after using the IFT. We congratulate the authors for their commendable work on the same. It is understood that MHs with large BD are predisposed to achieve a type 2 closure.[7]

With the advent of these surgical techniques, novel MH closure morphologies have also been seen. These patterns do not fit into the classical binary classification (open and close) provided by Kang et al.[8] Rossi et al.[2] proposed a new classification for MH closure patterns. Type 0 refers to the “open” MH configuration where the retinal pigmented epithelium (RPE) is bare and exposed to the vitreous cavity. It is further classified into three subcategories according to the configuration of the central rim of photoreceptors. The central photoreceptors may be adherent to the RPE (0A), elevated (0B), or edematous (0C). Type 1 refers to the closed MH configuration where the normal anatomy is regained. The recovery may be complete (1A) or there may be a residual defect in either the external (1B) or the internal (1C) retinal layers. Type 2 refers to the closed MH configuration but the foveal anatomy is interrupted by the tissue that was used to plug the hole. It is further classified into four subcategories according to the amount of tissue plugging the defect, that is, throughout all the retinal layers (2A), only the outer retina with reconstitution of normal inner retinal layers (2B), only the inner retina with reconstitution of normal outer retinal layers (2C), and only a bridging filling tissue (H-shape) without any reconstitution of normal retinal layers.[2] This classification considers the extent, the type, and the location of the anatomic restoration. Future studies evaluating the closure patterns using the IFT should use this classification instead of the older binary one.

Although the anatomical outcome is better with the IFT, the visual outcome has been found to be similar to that of the conventional ILM peeling technique.[9] Future studies should focus on finding new OCT biomarkers that can predict the visual outcome in large MHs using the IFT. Further, studies should be performed to evaluate the changes in macular sensitivity by using tests such as microperimetry and multifocal electroretinogram as well as to find preoperative OCT biomarkers predicting a better gain.