Histopathologic and Electron Microscopic Features of Internal Limiting Membranes in Maculopathies of Various Etiologies

Purpose: To report micro- and ultrastructural features of internal limiting membranes (ILMs) in various maculopathies and to evaluate the effects of indocyanine green (ICG) and triamcinolone acetonide (TA) on epiretinal proliferations associated with ILM and on retinal cleavage plane. Methods: ILMs from various maculopathies were evaluated regarding presence or absence of membrane-associated cells, type of cells and ILM thickness based on routine histopathology, immunohistochemistry and transmission electron microscopy (TEM). Results: Thirty ILM specimens were enrolled; 25 of which were evaluated by histopathology and immunohistochemistry and 5 by TEM. ICG only had been used in 17 specimens, TA in 4, and both agents in one specimen. The majority of specimens were immunoreactive for glial fibrillary acidic protein and neuron specific enolase. No significant difference in specimen cellularity and alteration of cleavage plane was noted between ICG-stained and non-ICG-stained ILMs or between TA-assisted and non-TAassisted ones. Excluding central retinal vein occlusion (CRVO) cases, acellularity was not observed in any of ILMs from diabetic macular edema (DME), cystoid macular edema (CME), and traumatic macular hole (TMH) eyes. TEM disclosed ILM thickening and cellularity in DME as compared to CRVO. Conclusion: Acellular membranes from CRVO maculopathy may be a sequel of acute retinal ischemia. Thickened diabetic ILMs with high cellularity may be related to chronic activation of Muller cells. No obvious influence of ICG or TA on epiretinal cellularity was detected and the dyes seem to have no significant effect on cleavage plane.