Comparative Study of Decellularized Human Amniotic Membrane Hydrogel and Inverted Internal Limiting Membrane Flap in Idiopathic Large Macular Holes

Overview

The human amniotic membrane (hAM) patch, introduced by Rizzo et al. in 2018, showed a 100% anatomical success rate for large or failed macular holes over a 6-month follow-up. Despite its regenerative properties like promoting angiogenesis and having low immunogenicity, its clinical use is limited by challenges such as trimming to fit small holes and complications during insertion. To overcome these issues, decellularized amniotic membrane (dAM) has been processed into a hydrogel form, enhancing its applicability and allowing it to be used as an injectable hydrogel for minimally invasive therapies. While dAM hydrogels have been used in various medical fields, their application in intraocular surgery is new. This study proposes using dAM hydrogel for large macular hole closure, comparing its effectiveness to the inverted ILM flap technique in a randomized controlled trial.

A macular hole (MH) is a neuroepithelial defect in the macular area of the retina. The estimation of macular hole incidence about 33 of every 10,000 person in individuals older than 55 years old1. The female-to-male ratio is 2 to 3:1. Idiopathic macular hole (IMH) is MHs occurring independently of primary ocular diseases such as trauma and vitreoretinopathy2 and represents the predominant subtype of MH, constituting approximately 83%1. There is a 5% to 15% risk of developing macular hole in the other eye if a macular hole develops in one eye.1 In 1988, Gass proposed a classification system for idiopathic macular holes, as well as a new hypothesis for its pathogenesis, which emphasizes the role of the vitreo-macular tangential traction in the formation of macular holes3. Macular hole closure can occurred spontaneously in approximately 5-10% cases in early stages. Pars plana vitrectomy with internal limiting membrane (ILM) peeling and gas tamponade has been the standard of care of small size macular hole treatment with success rate more than 90%4. However, in large macular hole more than 400 um, the success rate is lower. Previous study showed closure rate of large macular hole \> 400 μm is 56% with poor visual outcome.4,5 Several new techniques have been described to improve anatomical and functional outcomes in cases of large macular holes by inserting alternative tissues into the macular hole, such as the ILM flap, human amniotic membrane patch6, or retinal tissue implantation, to promote anatomical closure and improve visual acuity. The utilization of ILM flap coverage has emerged as an effective surgical approach for treating large, full-thickness idiopathic MH and myopic MH. This technique was initially introduced in 1999, showing promising results in enhancing macular hole closure rates through ILM peeling. Several subsequent studies 7-9 have further substantiated the efficacy of ILM flap coverage, making it the standard surgical treatment for large macular hole cases. However, this technique is often hindered by limitations related to the technical complexity of surgery and the risk of retinal trauma. The human amniotic membrane (hAM) patch, proposed by Rizzo et al. in 20186, serves as another alternative technique for large or failed macular hole cases. The anatomical success rate was 100% during the 6 months follow-up. The exceptional biological properties of hAM, including its promote angiogenesis10, low immunogenicity11, and anti-inflammatory11,12, anti-fibrotic13, and antibacterial characteristics14, make it highly suitable for regenerative medicine and intraocular implantation. However, the clinical application of thin hAM sheets is limited by several challenges, such as the difficulty of trimming it to fit very small hole sizes (\< 0.2 cm), tissue loss after insertion into the PPV port, and complications during the insertion of the hAM patch into the hole. To address these limitations, processing decellularized amniotic membrane (dAM) tissue into a hydrogel form has enhanced its processability and applicability15. This transformation allows it to be used as an injectable hydrogel for minimally invasive therapies and facilitates its manipulation into the macular hole. dAM hydrogels have been applied in various fields, including skin repair, cardiac treatment, cartilage regeneration, endometrial regeneration, vascular grafts, dental pulp regeneration, and as cell culture/carrier platforms. However, their use in intraocular surgery has not yet been established. Additionally, the benefits of dAM hydrogel over hAM tissue include lower immunogenicity due to the decellularization processs since the resident cells may cause intense host immunologic reactions after transplantation and transplant rejection and the homogeneous distribution of biochemical substances within the hydrogel structure.15 In this study, we will be the first to propose a new technique and invention for closing large macular holes using human amniotic membrane hydrogel filling in the hole after standard ILM peeling. We conducted a randomized controlled trial to compare the anatomical and visual outcomes of the inverted ILM flap technique (IFT) with the dHM hydrogel technique in idiopathic large macular holes with a minimum diameter (MD) greater than 400 μm.