Review INTERNAL LIMITING MEMBRANE PEELING IN MACULAR HOLE SURGERY; WHY, WHEN, AND HOW? IRINI P. CHATZIRALLI, MD, PHD,* PANAGIOTIS G. THEODOSSIADIS, MD, PHD,* DAVID H. W. STEEL, MBBS†‡ Purpose: To review the current rationale for internal limiting membrane (ILM) peeling in macular hole (MH) surgery and to discuss the evidence base behind why, when, and how surgeons peel the ILM. Methods: Review of the current literature. Results: Pars plana vitrectomy is an effective treatment for idiopathic MH, and peeling of the ILM has been shown to improve closure rates and to prevent postoperative reopening. However, some authors argue against ILM peeling because it results in a number of changes in retinal structure and function and may not be necessary in all cases. Furthermore, the extent of ILM peeling optimally performed and the most favorable techniques to remove the ILM are uncertain. Several technique variations including ILM flaps, ILM scraping, and foveal sparing ILM peeling have been described as alternatives to conventional peeling in specific clinical scenarios. Conclusion: Internal limiting membrane peeling improves MH closure rates but can have several consequences on retinal structure and function. Adjuvants to aid peeling, instrumentation, technique, and experience may all alter the outcome. Hole size and other variables are important in assessing the requirement for peeling and potentially its extent. A variety of evolving alternatives to conventional peeling may improve outcomes and need further study. RETINA 0:1–13, 2017 I diopathic full thickness macular hole (FTMH) is a vitreomacular interface disorder, which can lead to severe visual impairment. 1 It is estimated that it is present in 33 of every 10,000 individuals older than 55 years, whereas the incidence has been reported to be 4 to 8.7/100,000 per year, with female-to-male ratio to be 2 to 3:1. 2,3 Gass classified MHs into four stages based on careful fundoscopy; in Stage I, a central yellow spot is observed at the foveal center, with loss of the foveal depression (Stage Ia), which can be fol- lowed by the formation of a ring shaped yellow reflex (Stage Ib) without a full thickness defect. In Stage II, a small FTMH (,400 mm) is formed, usually with a visible operculum. In Stage III, the FTMH widens to more than 400 mm in diameter, but complete pos- terior vitreous detachment has not yet occurred, whereas Stage IV is the same as Stage III after com- plete vitreous separation from the disk. 4 In 2013, the International Vitreomacular Traction Study Group proposed an anatomical classification of vitreoretinal interface disorders using spectral domain optical coherence tomography (SD-OCT) and defined FTMH as “interruption of all retinal layers extending from internal limiting membrane (ILM) to the retinal pig- ment epithelium (RPE),” hence classifying precursor From the *Second Department of Ophthalmology, National and Kapodistrian University of Athens, Athens, Greece; †Sunderland Eye Infirmary, Sunderland, United Kingdom; and ‡Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom. None of the authors has any financial/conflicting interests to disclose. Reprint requests: David H. W. Steel, MBBS, Sunderland Eye Infirmary, Queen Alexandra Road, Sunderland, SR2 GHP, United Kingdom; e-mail: david.steel@ncl.ac.uk 1 Copyright ª by Ophthalmic Communications Society, Inc. Unauthorized reproduction of this article is prohibited.