Taut Internal Limiting Membrane Causing Diffuse Diabetic Macular Edema after Vitrectomy: Clinicopathological Correlation

Abstract

Aims: To describe 2 cases of diffuse diabetic macular edema (DME) after diabetic vitrectomy caused by a taut internal limiting membrane (ILM), with clinicopathological correlation. Methods: Interventional case series with immunohistochemical analysis. Results: Two patients were referred for unresponsive diffuse DME after pars plana vitrectomy with removal of the posterior hyaloid. Clinically, a taut ILM was noted over the fovea, and its removal resulted in rapid and long-term resolution of the edema, confirmed by optical coherence tomography with visual acuity improvement. Histopathology with immunostaining revealed a segment of ILM with an inner monolayer of cytokeratin-positive (retinal pigment epithelial cells) and/or glial fibrillary acidic protein-positive cells with smooth muscle actin immunoreactivity. Conclusions: A taut ILM can cause diffuse DME after vitrectomy, and its removal can restore the normal foveal contour and improve visual acuity. Tangential tractional forces from contractile cells propagated across the fovea via the ILM appear to be the etiology.

Surgical Management of Diabetic Macular Edema

“…As smooth muscle actin suggests myofibroblastic differentiation and the contractile ability of the RPE and glial cells, these changes likely caused tangential traction that was relieved by ILM peeling. 60 This tangential traction that can be exerted by the ILM was also imaged by Abe and colleagues. They performed a retrospective case series of 26 DME eyes imaged with spectral domain OCT to identify both traction seen on tomography and fine folds seen on 3 dimensional imaging.…”

The Time to Focus on the Imaging of Posterior Vitreous and Vitreoretinal Interface by Optical Coherence Tomography

“…In focal type of PTILM, ILM exists striae while in diffuse type, there is a glistening in the posterior pole. OCT reveals the edema in our retina without manifest traction [31,32]. It has been considered that PTILM might be develop due to the tangential traction of the ILM onto the distant retina because ILM has no elasticity.…”

“…This finding can be distingiushed from a TTPH and VMTS by the absence of an attached or partially attached hyaloid. Additionally, PTILM has hyper-reflective than normal reflective ILM and it has not any VMA and diffuse retinal edema [31,32]. Postvitrectomy taut ILM usually develops in first one-two months following PPV with hyaloid removal.…”

“…It has been considered that PTILM might be develop due to the tangential traction of the ILM onto the distant retina because ILM has no elasticity. Based on the histopathological examinations of PTILMs, it has been observed that PTILM has contractile cellular elements such as retinal pigment epithelium/glia cells having smooth muscle actin [31,32].…”

Surgical Management and Techniques

“…The ILM of diabetic eyes can contain modified fibroblasts with contractile properties. Its removal may theoretically reduce the contractive stimulus, even if not visible with SD-OCT [41] . Furthermore, it may prevent a relapse of ERM formation, since the ILM peeling removes a scaffold for secondary membrane growth [42] .…”