Early and late inner retinal changes after inner limiting membrane peeling

Abstract

Pars plana vitrectomy and inner limiting membrane (ILM) peeling are standard procedures for macular hole and epiretinal membrane surgery. However, ILM peeling is known to cause mechanical traumatic changes to the retinal nerve fiber layer. Recently there have been numerous reports of anatomical changes in the macula after ILM removal. A comprehensive review of the literature. The earliest change in the macula after ILM peeling is post-operative swelling of the arcuate retinal nerve fiber layer (SANFL), which disappears within the 3 month; the swelling is not detected on biomicroscopic fundus examination but appears as hypoautofluorescent arcuate striae in the macular region on infrared and autofluorescence imaging, with corresponding hyperreflectant swelling demonstrated on spectral-domain optical coherence tomography (OCT). SANFL is followed by dissociated optic nerve fiber layer defect, faintly visible on fundus examination and corresponding on OCT to "dimples" in the inner retinal layers. The en face tomographic aspect of this defect appears as concentric macular dark spots. Post-operative foveal displacement toward the optic disc might be responsible for the stretching and thinning of the retinal parenchyma in the temporal subfield and the thickening of the nasal macula. This shortening of the papillofoveal distance after surgery is probably secondary to axonal transport and contractility alterations in the nerve fiber layer, which might also account for apoptotic and atrophic degeneration of the peripapillary retinal nerve fiber layer. Ganglion cells do not seem to be affected by ILM peeling, even if the ganglion cell complex loses some volume because of trauma to the Müller cells contained in the ganglion cell layer. Despite its clear indication in macular hole and epiretinal membrane surgery, ILM peeling is a traumatic procedure that has acute effects on the underlying inner retinal layers. Further investigation of these subclinical changes may assist in aiding the development of minimally traumatic techniques for ILM removal.