Role of Inflammation in Classification of Diabetic Macular Edema by Optical Coherence Tomography

Abstract

Diabetic macular edema (DME) is the abnormal accumulation of fluid in the subretinal or intraretinal spaces in the macula in patients with diabetic retinopathy and leads to severely impaired central vision. Technical developments in retinal imaging systems have led to many advances in the study of DME. In particular, optical coherence tomography (OCT) can provide longitudinal and microstructural analysis of the macula. A comprehensive review was provided regarding the role of inflammation using OCT-based classification of DME and current and ongoing therapeutic approaches. In this review, we first describe the pathogenesis of DME, then discuss the classification of DME based on OCT findings and the association of different types of DME with inflammation, and finally describe current and ongoing therapeutic approaches using OCT-based classification of DME. Inflammation has an important role in the pathogenesis of DME, but its role appears to differ among the DME phenotypes, as determined by OCT. It is important to determine how the different DME subtypes respond to intravitreal injections of steroids, antivascular endothelial growth factor agents, and other drugs to improve prognosis and responsiveness to treatment.

Malfunction of outer retinal barrier and choroid in the occurrence and progression of diabetic macular edema

“…Pericytes have a critical role in maintaining of BRB, by liberating a lipid mediator which modulates it[ 17 ]. Retinal Müller cells and astrocytes stabilize the tight junctions between the endothelial cells[ 18 ], whereas microglia produces soluble factors which are important for vesicular communication[ 15 ].…”

“…These tight, adherens and gap junctions control the transport of fluids and solutes between the choroidal capillaries and the photoreceptor layers, thus maintaining the integrity of the retina[ 18 ]. It was proved that the RPE cells express major histocompatibility complex molecules, adhesion molecules and cytokines, thus playing an important role in immune processes[ 20 ].…”

“…Based on the OCT appearance, three major types of DME were individualized: diffuse sponge-like thickening type, cystoid type (thickening of the fovea with intraretinal cysts) and serous retinal detachment (SRD) type (thickening of the fovea with subretinal fluid)[ 18 , 31 , 32 ].…”

“…Each of these lesions occurs in individual retinal layers, as follows: cystoid spaces are located mainly in the inner nuclear layer (INL) and outer plexiform layer (OPL); in SRD the extracellular fluid pools between the photoreceptors outer segments (PROS) and RPE; sponge-like retinal swelling at the fovea is identified in the OPL[ 33 ]. Whereas the sponge-like retinal swelling is frequently accompanied by abnormalities of the vitreo-macular interface causing the thickening of the retinal parenchyma at the level of the OPL[ 33 ], the presence of fluid in the subretinal space suggests the alteration of the outer BRB being caused by the migration of fluid from the retina through a weakened and permeable ELM or from the hyperpermeable vessels in the choriocapillaris through a dysfunctional RPE[ 18 , 32 ]. In the early stage of the disease the subretinal fluid originates in the hyperpermeable choriocapillaris through a dysfunctional RPE and as the disease progresses in the breakdown of the outer BRB through a permeable ELM[ 34 , 35 ].…”

Saudi Arabia Guidelines for diabetic macular edema

“…82 Intravitreal corticosteroids can improve the outcomes of DME by inhibiting the release of inflammatory mediators and leukostasis, which are significant contributors to the development of DME. 28 Initially, intravitreal injection of triamcinolone acetonide (TA) was studied and exhibited significant improvements in visual and anatomical outcomes among patients with DME. [83][84][85] Triamcinolone acetonide combined with laser therapy was found to be as effective as ranibizumab plus laser therapy in pseudophakic eyes.…”