![]() 28, 29 The role of macrophages in the pathogenesis of idiopathic ERMs has yet to be determined hyalocytes are of macrophage lineage, and some glial cells are specialized macrophages. 26 – 28 Hyalocytes, likely originating from cortical vitreous remnants following anomalous PVD, have been identified in ERMs, and the transdifferentiation of hyalocytes may play a central role in ERM formation. ![]() ![]() 26 However, the exact etiology of these glial cells remains unclear there is evidence that these glial cells derive from Müller cells or astrocytes. 25 Glial cells are thought to predominate in early idiopathic ERMs. The precise identification of the cells and cell lineages involved in the pathogenesis of idiopathic ERMs has been hindered by the ability of these cells to transdifferentiate. 23 Moreover, residual vitreous cells may promote the migration of cells or projection of cell processes through an otherwise intact ILM. 22 Vitreoretinal traction induces the production of cytokines, such as basic fibroblast growth factor and nerve growth factor, that stimulate the residual vitreous cells to proliferate. 21 When vitreoschisis occurs, remnants of the cortical vitreous are left in the premacular region. 20 Anomalous PVD occurs when vitreous liquefaction outpaces vitreoretinal adhesion weakening, resulting in vitreoschisis and vitreoretinal traction. 19 An alternative theory has been proposed that involves the concept of anomalous PVD. 17, 18 However, this theory has been challenged by the finding that breaks are exceedingly rare in the ILMs associated with ERMs. A classically accepted theory is that PVD causes breaks in the internal limiting membrane (ILM) that allow cells to migrate to the inner surface of the retina where they form an idiopathic ERM. 16 Numerous theories have been proposed to explain the association between PVD and idiopathic ERM. PVD has been described in up to 95% of cases of idiopathic ERM. This can precipitate the separation of the vitreous from its posterior attachments, an occurrence known as posterior vitreous detachment (PVD). As the vitreous ages, it liquefies and its retinal adhesions weaken. 15 The vitreous adheres to the inside of the eye at the posterior lens capsule, peripheral retina, retinal vessels, perimacular region, and optic disk. The vitreous is the transparent gel that occupies the posterior segment of the eye and is composed primarily of water, collagen, hyaluronan, and hyalocytes. Herein, we review the basics of ERMs and propose an OCT-based classification system for ERMs. In order to fully harness these technological advances, a standardized classification system must be devised. 14 Imaging techniques, such as spectral-domain optical coherence tomography (SD-OCT) with three-dimensional reconstruction, have been introduced for this purpose. However, recent advances in imaging have allowed clinicians to more accurately diagnose and characterize ERMs and their associated complications, such as vitreomacular traction and macular hole. 6 – 13 Historically, ERMs were diagnosed and classified based on clinical examination findings alone. 2 Furthermore, an ERM can be classified as either idiopathic or secondary based on etiology. Clinically, an ERM can be classified as either cellophane macular reflex or preretinal macular fibrosis based on severity. 4, 5ĮRM is a pathologic fibrocellular membrane that lies immediately superjacent to the inner surface of the retina. The prevalence of ERM varies from 2.2% to 28.9% depending on the population being studied. 3 Most ERMs occur in individuals older than 50 years, and the prevalence of ERM increases as age increases. 2 Numerous potential risk factors for the development of an ERM have been identified, including race, ethnicity, sex, smoking, diabetes, arteriolar narrowing, and hypercholesterolemia however, the most consistently identified risk factor is age. 1 It has been estimated that 30 million people of advanced age in the US have an ERM in at least one eye. The symptoms associated with ERMs, especially metamorphopsia, can impair vision-related quality of life. ![]() The clinical presentation of an ERM can range from completely asymptomatic, diagnosed on routine examination, to profoundly symptomatic with metamorphopsia, micropsia or macropsia, photopsia, decreased visual acuity (VA), and loss of central vision. Epiretinal membrane (ERM), also known as macular pucker or cellophane maculopathy, is a disorder of the vitreomacular interface that can cause visual impairment.
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