Potential role of Müller cells in the pathogenesis of macropsia associated with epiretinal membrane: a hypothesis revisited

A classification of idiopathic epiretinal membrane based on foveal avascular zone area using optical coherence tomography angiography

OBJECTIVE

To evaluate the characteristics and prognoses of idiopathic macular epiretinal membrane (iERM) using a classification based on the foveal avascular zone (FAZ) area.

METHOD

IERMs were classified into four stages based on the FAZ area. Baseline FAZ-related parameters, pre-and postoperative central macular thickness (CMT), and best corrected visual acuity (BCVA) were observed and compared between different stages. The correlations of structural parameters with pre-and postoperative logMAR BCVA were analyzed.

RESULTS

162 iERM eyes were enrolled, including 105 eyes followed up for 12 months after surgery. The preoperative BCVA was better at the early stage. Postoperative BCVA at Stages 2 and 3 were better compared to Stage 4. The early stage was associated with thinner CMT pre-and postoperatively. However, there was no significant difference in CMT between postoperative Stages 1 and 2 or Stages 3 and 4. Preoperative logMAR BCVA was negatively correlated with FAZ area, perimeter, and FD-300 and was positively correlated with CMT and acircularity index (AI). CMT correlated positively with BCVA for each stage, except Stage 4; FAZ area, perimeter, and FD-300 had a negative correlation at Stage 1. Baseline BCVA and CMT positively correlated with BCVA at the last follow-up, while FAZ area and FD-300 were negatively correlated. Baseline BCVA had a positive correlation for each stage, except Stage 1; FD-300 had a negative correlation at Stages 2 and 3; CMT had a positive correlation at Stage 3.

CONCLUSION

A classification based on the FAZ area was established innovatively. This classification can reflect the progression of iERM and is helpful to the postoperative prognosis.

Analysing early changes of photoreceptor layer thickness following surgery in eyes with epiretinal membranes

BACKGROUND/OBJECTIVES

To analyse short-term changes of mean photoreceptor thickness (PRT) on the ETDRS-grid after vitrectomy and membrane peeling in patients with epiretinal membrane (ERM).

SUBJECTS/METHODS

Forty-eight patients with idiopathic ERM were included in this prospective study. Study examinations comprised best-corrected visual acuity (BCVA) and optical coherence tomography (OCT) before surgery, 1 week (W1), 1 month (M1) and 3 months (M3) after surgery. Mean PRT was assessed using an automated algorithm and correlated with BCVA and central retinal thickness (CRT).

RESULTS

Regarding PRT changes of the study eye in comparison to baseline values, a significant decrease at W1 in the 1 mm, 3 mm and 6 mm area (all p-values < 0.001), at M1 (p = 0.009) and M3 (p = 0.019) in the central 1 mm area, a significant increase at M3 in the 6 mm area (p < 0.001), but no significant change at M1 in the 3 mm and 6 mm area and M3 in the 3 mm area (all p-values > 0.05) were observed. BCVA increased significantly from baseline to M3 (0.3LogMAR-0.15LogMAR, Snellen equivalent = 20/40-20/28 respectively; p < 0.001). There was no correlation between baseline PRT and BCVA at any visit after surgery, nor between PRT and BCVA at any visit (all p-values > 0.05). Decrease in PRT in the 1 mm (p < 0.001), 3 mm (p = 0.013) and 6 mm (p = 0.034) area after one week correlated with the increase in CRT (449.9 µm-462.2 µm).

CONCLUSIONS

Although the photoreceptor layer is morphologically affected by ERMs and after their surgical removal, it is not correlated to BCVA. Thus, patients with photoreceptor layer alterations due to ERM may still benefit from surgery and achieve good functional rehabilitation thereafter.

Pathophysiology and clinical aspects of epiretinal membrane - review

The epiretinal membrane (ERM) is a pathological tissue formed at the vitreoretinal interface. The formation of this tissue is associated with numerous symptoms related to disturbances of vision. These types of lesions may arise idiopathically or be secondary to eye diseases, injuries and retinal surgeries. ERM tissue contains numerous cell types and numerous cytokines, which participate in its formation. The aim of this paper is to summarize information about the etiology, epidemiology, pathophysiology and treatment of ERM, with a brief description of the main cells that build the ERM - as well as the cytokines and molecules related to ERM pathogenesis - being provided in addition.

Total and horizontal distances of the foveal stereotaxic displacement can be prognostic indicators for patients with idiopathic epiretinal membrane

Introduction

This study aimed to examine the foveal stereo deviations in the different ectopic inner foveal layer (EIFL) stages of idiopathic epiretinal membrane (iERM) and assess its predictive utility for the baseline and postoperative best-corrected visual acuity (BCVA).

Methods

Based on the calculational combination of foveal displacements in the horizontal and vertical axial optical coherence tomography (OCT) images, the foveal stereotaxic displacement was estimated through the total distance (TD, the distance from the foveal bottom to the inner edge of displaced central foveal) and horizontal distance (HD, projection of the TD in the retinal plane). The preoperative TD, HD, and other OCT- and OCT angiography (OCTA)-related indicators were obtained. The correlations between structural parameters and baseline and postoperative BCVA were evaluated through correlation and multiple linear regression analyses.

Results

In patients with advanced EIFL stage, there was a significant increase in the HD, TD, baseline log of the minimum angle of resolution unit for BCVA, central macular thickness (CMT), acircularity index, and incidence of microcystic macular edema (MME; p &lt; 0.05). Further, they showed a decreased foveal avascular zone (FAZ) area and perimeter (p &lt; 0.001). HD, TD, CMT, MME, FAZ area, and FAZ perimeter were significantly correlated with the baseline and postoperative BCVA (p &lt; 0.05). TD had the highest correlation indexic and was an individual predictor of the baseline and postoperative BCVA. Moreover, FD-300 and MME were individual predictors of postoperative BCVA.

Discussion

Stereoscopic foveal deviations significantly correlated with the baseline and postoperative visual acuity. TD may be used as an independent prognostic factor for BCVA.

Optical analysis of Müller glia cells as light transporters through the retina

One and half decades ago, Müller glia cells of the retina became subjects of extended research as optical waveguides. It was demonstrated that outside the fovea, these cells are capable of providing light transmission through the thicker parts of the retina from the vitreous surface to the photoreceptor cells. We combined optical modeling of the eye's optical system with numerical methods that describe light guiding within Müller cells to analyze efficiency of light capture and guidance at different peripheral positions. We show that higher order guided modes play an important role, especially in the case of higher incidence angles and extended geometry of the electromagnetic field distributions predicted by the eye's optical model. We analyze the mode structure excited at different retinal peripheral positions and show that actual construction of these cells optimizes light guiding. Our results refine previously published modeling results regarding Müller cells as waveguides and provide extension to the whole area of the retina.

Influence of postoperative ectopic inner foveal layer on visual function after removal of idiopathic epiretinal membrane

Purpose

To investigate the functional and anatomical parameters and their postoperative changes according to the ectopic inner foveal layer (EIFL) staging scheme for idiopathic epiretinal membrane (ERM).

Methods

In this prospective study, patients with idiopathic ERM underwent pars plana vitrectomy and ERM removal, and were followed-up for 6 months. The associations of EIFL with pre- and postoperative functional and anatomical parameters were analyzed.

Results

A total of 84 eyes (84 patients) were included: 39 (46.4%), 33 (39.3%), and 12 (14.3%) as EIFL stages 2, 3, and 4, respectively. At 6 months after surgery, the mean best-corrected visual acuity (BCVA) significantly improved in all EIFL stages (P ≤ 0.003); however, metamorphopsia improved only in eyes with EIFL stage 2 (P = 0.039) and 3 (P = 0.011). The aniseikonia and foveal avascular zone (FAZ) area showed no significant postoperative changes in any of the EIFL stages. Both preoperatively and during 6 months after surgery, the EIFL stage showed a significant correlation with BCVA (P ≤ 0.033), metamorphopsia (P ≤ 0.008), central macular thickness (P < 0.001), and FAZ parameters (P ≤ 0.016) at each time point, but not with aniseikonia. Significant correlations of EIFL thickness with BCVA (P = 0.028) and metamorphopsia (P = 0.006) before surgery were not persistent after surgery.

Conclusion

Both pre- and postoperatively, the staging of EIFL, rather than its thickness, is a simple and adequate surrogate marker for visual acuity and metamorphopsia in eyes with idiopathic ERM.

Smaller Foveal Avascular Zone in Deep Capillary Plexus Is Associated with Better Visual Acuity in Patients after Macula-off Retinal Detachment Surgery

Purpose

To associate the change in the foveal avascular zone (FAZ) and vessel density (VD) with final best corrected visual acuity (BCVA) in eyes after macula-off rhegmatogenous retinal detachment surgery, and to investigate the evolution of FAZ and VD during 12 months of follow-up.

Methods

We prospectively evaluated 47 patients with macula-off rhegmatogenous retinal detachment and healthy fellow eyes. At 1.5, 3.0, 6.0, and 12.0 months postoperatively, optical coherence tomography angiography scans were obtained from both eyes on a 3.0 × 3.0 mm macula-centered grid. En face images of the superficial vascular plexus, intermediate capillary plexus and deep capillary plexus were used to quantify FAZ and VD. BCVA was assessed with ETDRS-charts (logarithm of the minimal angle of resolution).

At 12 months postoperatively, the association between the change in optical coherence tomography angiography parameters and visual function in study eyes was evaluated using the Spearman correlation coefficient. We calculated the BCVA difference and the percentage difference of FAZ and VD between the study and control eye. The evolution of FAZ and VD was investigated with linear mixed-effects models with nested random effects (eyes nested within patients).

Results

At 12 months postoperatively, FAZ difference of the deep capillary plexus and BCVA difference were correlated (P = 0.0004, r_s = 0.5). Furthermore, there was no evidence that FAZ and VD changed during follow-up.

Conclusions

Although FAZ and VD remained stable during 12 months after surgery for macula-off rhegmatogenous retinal detachment, a smaller FAZ in the deep capillary plexus is associated with better BCVA.

Translational relevance

Reduction in FAZ area may be caused by angiogenesis to counteract ischemia, therefore therapeutic stimulation of angiogenesis could be beneficial to visual recovery.