Abnormal focal macular electroretinograms in eyes with idiopathic epimacular membrane

Epiretinal membrane: an overview and update

Epiretinal membrane (ERM) is a frequently diagnosed macular disease associated with aging, characterized by a fibrous membrane forming on the internal limiting membrane (ILM) and leading to visual dysfunctions such as metamorphopsia. Various hypotheses regarding the pathology of metamorphopsia have been proposed; however, the complete pathophysiologic mechanism underlying ERM remains unclear. Optical coherence tomography (OCT) provides detailed images enabling precise diagnosis and characterization of ERM, with several recent studies using the latest OCT imaging techniques. Surgical removal of ERM is the only treatment option; however, criteria for surgical intervention are not established, complicating the decision-making processes. Furthermore, the debate on whether simultaneous peeling of the ILM during ERM surgery enhances outcomes or poses unnecessary risks is ongoing, with no definite conclusion having yet been reached. This review also focuses on epiretinal proliferation, which is different from ERM and is characteristic of lamellar macular hole (LMH). Recently, diagnostic criteria for LMH and related diseases were proposed. Reports on effective surgical procedures for LMH exist, although more research is needed to confirm the long-term outcomes. Thus, this review article aims to provide an overview and updated knowledge of ERM, LMH, and related diseases.

Epiretinal Membrane Impairs the Inner Retinal Layer in a Traction Force-Dependent Manner

Purpose

To investigate the relationship between retinal traction force and impairment of the inner retinal layer in patients with epiretinal membrane (ERM).

Design

Nonrandomized, retrospective consecutive case series.

Participants

Two hundred nine eyes of 201 patients with idiopathic ERM who underwent vitrectomy for idiopathic ERM were enrolled.

Methods

Retinal folds caused by ERM were visualized using en face OCT, and the maximum depth of retinal folds within the parafovea (MDRF) was measured. Focal macular electroretinogram (ERG) was used to measure the amplitude and implicit time of each component for the ERM eyes and the normal fellow eyes. B-scan OCT images were used to measure the thicknesses of the inner nuclear layer (INL) and outer nuclear layer (ONL) + outer plexiform layer (OPL). Expression of α-smooth muscle actin (α-SMA) in surgically removed ERM specimens was quantified by reverse-transcription polymerase chain reaction.

Main Outcome Measures

We analyzed the relationship between MDRF and the relative amplitudes of focal macular ERG (affected eye/fellow eye), the relationships between MDRF and the mean INL thickness and ONL+OPL thickness, comparison of INL thickness and ONL+OPL thickness for each area when cases were classified according to MDRF localization in the ETDRS chart, and the relationship between MDRF and the relative expression of α-SMA in the ERM specimens.

Results

The MDRF significantly correlated with the relative amplitudes (affected eye/fellow eye) of b-waves and oscillatory potentials (r = -0.657, P = 0.015; r = -0.569, P = 0.042, respectively) and the mean INL thickness and ONL+OPL thickness (r = 0.604, P < 0.001; r = 0.210, P = 0.007, respectively). However, only the INL thickness progression rate was significantly correlated with the MDRF progression rate (r = 0.770, P < 0.001). On case stratification by localization of MDRF based on the ETDRS chart, in regions other than temporal regions, the INL thickness was significantly greater in regions with MDRF than in other regions. The MDRF significantly correlated with α-SMA expression in the ERM specimens (r = 0.555, P = 0.009).

Conclusions

The findings suggest that ERM impairs the inner retinal layer in a traction force-dependent manner.

Financial Disclosures

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Morphological Changes in Lamellar Macular Holes According to SD-OCT Examination over a Long Observation Period

BACKGROUND

The aim of this study was to evaluate the quantitative morphological changes in lamellar macular holes (LMHs) based on SD-OCT examinations and to assess the correlations among minimal retinal thickness (MRT), reading vision (RV), and best corrected visual acuity (BCVA) over a 36-month follow-up period.

METHODS

A group of 40 patients (44 eyes) with LMH was evaluated, with an average age of 69.87 (SD = 10.14). The quantitative parameters monitored in the follow-up period (at 0, 3, 6, 12, 18, 24, 30, and 36 months) were tested for normality of distribution by Shapiro-Wilk and Kolmogorov-Smirnov tests.

RESULTS

The RV and BCVA values were stable, and no significant changes were found at any of the check-ups during the 36-month follow-up period (BCVA p = 0.435 and RV p = 0.0999). The analysis of individual quantitative LMH parameters during the 36-month follow-up period did not demonstrate statistically significant differences: MRT (p = 0.461), Max RT temporal (p = 0.051), Max RT nasal (p = 0.364), inner diameter (ID) (p = 0.089), and outer diameter (OD) (p = 0.985).

CONCLUSIONS

The observations at 0, 6, 12, 18, 24, 30, and 36 months revealed moderate and significant correlations between RV and MRT. No significant correlation between BCVA and MRT was observed.

CORRELATION BETWEEN MACULAR MICROSTRUCTURES AND ANISEIKONIA AFTER IDIOPATHIC EPIRETINAL MEMBRANE REMOVAL

PURPOSE

To analyze the correlation between preoperative measurements of macular microstructures and aniseikonia after epiretinal membrane removal.

METHODS

This retrospective study included 32 eyes of 32 patients who underwent epiretinal membrane surgery and were followed up for 12 months. Spectral-domain optical coherence tomography was used to measure the thicknesses of the ganglion cell layer-inner plexiform layer, inner nuclear layer (INL), and outer retinal layer in macular microstructures. The new aniseikonia test was used to measure vertical and horizontal aniseikonia scores.

RESULTS

There was a significant decrease in central macular thickness and ganglion cell layer-inner plexiform layer thickness at 6 and 12 months postoperatively (all P < 0.001). Vertical aniseikonia scores, horizontal aniseikonia scores, and INL and outer retinal layer thicknesses did not show significant changes. Vertical aniseikonia scores and horizontal aniseikonia scores were significantly associated with INL thicknesses of each meridian at each follow-up time point (all P < 0.05). Preoperative vertical and horizontal INL thicknesses were correlated with vertical aniseikonia scores and horizontal aniseikonia scores at 12 months postoperatively (P = 0.014 and P = 0.002, respectively).

CONCLUSION

Aniseikonia values did not change after epiretinal membrane removal and were associated with INL thickness before and after surgery. Thus, preoperative INL thickness could be used as a predictor of surgical prognosis in epiretinal membrane patients.

Choroidal thickness in lamellar macular holes

PURPOSE

(1) To assess the thickness of the central choroid (BM-CSI) in swept-source optical coherence tomography (SS-OCT) examination of lamellar macular holes (LMHs). (2) To establish correlations between the thickness of the central choroid (BM-CSI) in the LHM and the parameters of best-corrected visual acuity and reading vision in patients with LMH.

METHODS

This prospective case-control study assessed a group of 30 patients (30 eyes) with LMHs and a control group of 45 patients (90 eyes). The thickness of the central choroid (BM-CSI) was measured with an SS-OCT device. The average choroidal thickness in the fovea was defined as average thickness in the central area of 1000 μm in diameter, according to the Early Treatment Diabetic Retinopathy Study (ETDRS). The results were correlated with best-corrected visual acuity (BCVA), and reading vision.

RESULTS

The average choroidal thickness in the study group (SG) with LMH was 160.34 μm (SD = 77.1), whereas in the control group (CG), it was 225.11 μm (SD = 93.8). The difference of 64.77 μm was statistically significant (p < 0.05). The BCVA was within the range between 0.7 (logMAR) and 0.1 (logMAR), with an average of 0.36 (logMAR) (SD = 0.23). Reading vision was within the range between - 0.2 (logMAR) and 0.3 (logMAR), with an average of 0.27 (logMAR) (SD = 0.12). A significant correlation between BCVA and the choroid (BM-CSI) was found. The correlation coefficient is average (r = 0.44) and positive. With better BCVA, a significantly thicker choroid (BM-CSI) can be observed. No significant correlation between BM-CSI and reading vision was found. The correlation coefficient value is minor (r = - 0.289), whereas lower values of BM-CSI can be observed with worse reading vision.

CONCLUSION

We suggest that the choroid may take part in the pathogenesis of LMH development. Its significant thinning may be responsible for the ischemic degenerative mechanism degenerating outer layers of retina, apart from tractional mechanism.

Macular dysfunction in patients with macula-on rhegmatogenous retinal detachments

AIMS

To assess macular function in patients with macula-on rhegmatogenous retinal detachments (RRDs) using focal macular electroretinography (FMERG).

METHODS

This is a prospective, observational case series of 27 patients diagnosed with a macula-on RRD. Foveal attachment was confirmed on spectral-domain optical coherence tomography. Eyes with any macular disorder, cataract, vitreous opacity or vitreous haemorrhage were excluded. FMERG was recorded in the affected and fellow eyes using a round stimulus 15° in diameter. The status of four retinal factors in the affected eyes was examined, that is, the number of involved quadrants, number of quadrants with retinal breaks, presence of an RRD invading the vascular arcade, and presence of a giant retinal tear. The implicit time and amplitude of the a-wave, b-wave and oscillatory potentials (OPs) were compared between the affected and fellow eyes using Wilcoxon signed-rank test. The influence of the four retinal factors on each FMERG component of the affected eyes was also evaluated using Mann-Whitney U test and Kruskal-Wallis test.

RESULTS

Significant reductions in the amplitudes of the a-waves (p=0.001), b-waves (p<0.001) and OPs (p=0.001) were observed in the affected eyes compared with the fellow eyes. There was no significant difference between the affected and fellow eyes in the implicit times of any components. None of the four retinal factors affected the parameters in the affected eyes.

CONCLUSION

Altered FMERG responses suggested the presence of macular dysfunction in eyes with macula-on RRDs.

Assessment of macular function in patients with idiopathic Epiretinal membrane by multifocal Electroretinography: correlation with visual acuity and optical coherence tomography

Background

This study evaluates the macular function changes in patients with idiopathic macular epiretinal membrane (ERM) by multifocal electroretinography (mfERG) and their correlations with visual acuity and central macular thickness (CMT) by optical coherence tomography (OCT).

Methods

Twenty eyes of 20 patients with ERM underwent OCT and mfERG examinations. The response amplitude densities and implicit times of mfERG were compared to the control fellow eyes. Correlation analyses among visual acuity, central macular thickness and mfERG values in the central two concentric rings were performed.

Results

The mfERG P1 response amplitude densities in ring 1–2 and P1 implicit time in ring1 were significantly changed in epiretinal membrane eyes compared with controls (P < 0.05). Multivariate stepwise linear regression analyses showed LogMAR visual acuity was significantly correlated with CMT (P = 0.004), and also with the P1 amplitude density in ring 1 (P = 0.002). CMT showed significant correlation with P1 implicit time in ring 2 (P = 0.013).

Conclusions

The mfERG abnormalities show macular function changes and correlate with visual acuity and central macular thickness in eyes with ERM. In first-order mfERG responses, P1 wave changes may be a sensitive functional measurement for ERM patients.

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

Pathophysiological explanations for metamorphopsia associated with retinal pathologies generally focus on photoreceptor organization disruption. However, the retinal microarchitecture is complicated, and we hypothesize that other retinal cells may also be involved. Metamorphopsia has been widely studied in eyes with epiretinal membranes and we revisit the idea that Müller cell displacement causes retinal macropsia. A PubMed query and related article search for the macula ultrastructure under normal and pathological conditions revealed an enormous amount of information, particularly ultrahigh definition optical coherence tomography and other retinal imaging modality studies. Findings of these imaging studies support our hypothesis that Müller cells, and not cone photoreceptors, are primarily responsible for macropsia in eyes with epiretinal membranes. More specifically, we conclude that displacement of Müller cell endfeet, and not photoreceptor cones, is a more likely the explanation for retinal macropsia associated with epiretinal membranes.

[Idiopathic epiretinal membranes: visual function impairment, morphological and functional features of retinal involvement]

By affecting different retinal layers, an idiopathic epiretinal membrane (iERM) produces changes in macular architectonics and functioning. Morphological and functional assessment of these patients using modern visualization methods and electroretinography contributes to a better understanding of pathogenetic mechanisms of iERM.

Assessment of Macular Function during Vitrectomy: New Approach Using Intraoperative Focal Macular Electroretinograms

Purpose

To describe a new technique to record focal macular electroretinograms (FMERGs) during vitrectomy to assess macular function.

Methods

Intraoperative FMERGs (iFMERGs) were recorded in ten patients (10 eyes) who undergo vitrectomy. iFMERGs were elicited by focal macular stimulation. The stimulus light was directed to the macular area through a 25 gauge (25G) glass fiber optic bundle. Background light was delivered through a dual chandelier-type light fiber probe. Focal macular responses elicited with combinations of stimulus and background luminances were analyzed.

Results

A stimulus luminance that was approximately 1.75 log units brighter than the background light was able to elicit focal macular responses that were not contaminated by stray light responses. Thus, a stimulus luminance of 160 cd/m² delivered on a background of 3 cd/m² elicited iFMEGs from only the stimulated area. This combination of stimulus and background luminances did not elicit a response when the stimulus was projected onto the optic nerve head. The iFMERGs elicited by a 10° stimulus with a duration of 100 ms and an interstimulus interval of 150 ms consisted of an a-, b-, and d-waves, the oscillatory potentials, and the photopic negative response (PhNR).

Conclusions

Focal ERGs with all components can be recorded from the macula and other retinal areas during vitreous surgery. This new technique will allow surgeons to assess the function of focal areas of the retina intraoperatively.

Evaluation of Macular Function Using Pattern Electroretinogram in Idiopathic Epiretinal Membrane

PURPOSE

Pattern electroretinogram (PERG) in idiopathic epiretinal membrane (ERM) was investigated to find the correlation of the ganglion cell function with postoperative visual acuity.

DESIGN

This was a retrospective consecutive chart review.

METHODS

Medical records of 24 eyes that underwent vitrectomy and membrane peeling for idiopathic ERM were reviewed retrospectively. The amplitude and implicit time of P50 and N95 in preoperative PERG were analyzed to find correlation with visual acuity and foveal thickness. The ratio of the parameters in involved eyes to those in healthy fellow eyes was calculated for analysis.

RESULTS

Visual acuity (logarithm of the minimum angle of resolution) improved from 0.53 at baseline to 0.34 at 6 months (P = 0.003). Foveal thickness decreased significantly from 488.3 μm at baseline to 374.7 μm (P = 0.001). The preoperative N95 amplitude ratio was significantly correlated with visual acuity at 6 months after ERM removal (r = -0.423, P = 0.040), whereas the amplitude of P50 and implicit time of both waves showed no significant correlation with postoperative visual acuity. The implicit time ratio of P50 (r = 0.530, P = 0.008) and N95 (r = 0.436, P = 0.033) showed significant correlation with preoperative foveal thickness on optical coherence tomography.

CONCLUSIONS

N95 amplitude in PERG was a predictor of visual outcomes after ERM surgery. These results suggest the correlation of postoperative visual acuity with the function of the ganglion cell layer, which is the closest cell layer to be affected by ERM.

Structural and functional predictors of visual outcome of epiretinal membrane surgery

PURPOSE

To evaluate the utility of preoperative optical coherence tomography (OCT) and multifocal electroretinography (mfERG) in prediction of visual outcomes after idiopathic epiretinal membrane (ERM) surgery.

DESIGN

Retrospective, observational case series.

METHODS

One hundred eyes of 100 patients with idiopathic unilateral ERM who underwent vitrectomy for ERM removal were retrospectively reviewed. Correlations between preoperative data (OCT and mfERG) and final best-corrected visual acuity (BCVA) were investigated using Pearson correlation analysis. One-way analysis of variance (ANOVA) was used to determine whether final BCVA and mfERG values differed among subgroups varying in photoreceptor integrity status. Receiver operating characteristic (ROC) curve analysis was performed to obtain a cutoff value of the P1 implicit time predicting visual recovery (final BCVA ≥20/25).

RESULTS

BCVA significantly improved, and 65 of 84 eyes (77%) achieved visual recovery of more than 2 Snellen lines after ERM surgery. Final BCVA was significantly correlated with preoperative photoreceptor integrity and P1 implicit time. The area under the ROC (AUROC) curve was statistically significant when P1 implicit time was examined, and the cutoff value for good visual prognosis was 40.81 msec (sensitivity: 72.7%; specificity: 81.3%).

CONCLUSION

Photoreceptor disruption detected by OCT and P1 implicit time delay on mfERG were significant predictors of poor visual recovery after ERM surgery.

Different collagen types define two types of idiopathic epiretinal membranes

AIMS

To identify differences in extracellular matrix contents between idiopathic epiretinal membranes (IEM) of cellophane macular reflex (CMRM) or preretinal macular fibrosis (PMFM) type.

METHODS AND RESULTS

Idiopathic epiretinal membranes were analysed by light and quantitative transmission electron microscopy, immunohistochemistry and Western blotting. Substantial differences between CMRM and PMFM were observed regarding the nature of extracellular fibrils. In CMRM the fibrils were thin, with diameters between 6 and 15 nm. Between the fibrils, aggregates of long-spacing collagen were observed. In PMFM the diameters of fibrils measured either 18-26 or 36-56 nm. Using immunogold electron microscopy, 6-15 nm fibrils in CMRM were labelled for collagen type VI, while the fibrils in PMFM remained unstained. Using Western blotting and immunohistochemistry, a strong signal for collagen type VI was observed in all CMRM, while immunoreactivity was weak or absent in PMFM. In contrast, PMFM showed immunoreactivity for collagen types I and II, which was weak or absent in CMRM. Both types of membranes showed immunoreactivity for collagen types III and IV, laminin and fibronectin with similar intensity.

CONCLUSION

The presence of high amounts of collagen type VI in CMRM and the relative absence of collagen types I and II is the major structural difference to PMFM.

Correlation between thickening of the inner and outer retina and visual acuity in patients with epiretinal membrane

PURPOSE

The purpose of this study was to examine the relationship between thickening of the inner and outer retinal layers and visual acuity in patients with idiopathic epiretinal membrane.

METHODS

We examined 30 eyes of 30 patients and 25 eyes of 25 healthy volunteers as age-matched normal control subjects. The inner (between the vitreoretinal interface and the outer border of inner plexiform layer), outer, and full retinal thickness at the fovea, parafovea, and perifovea were measured using spectral-domain optical coherence tomography.

RESULTS

Thickening ratios of both the inner and outer retina were greater in the fovea than in the other macular regions (P < 0.0001). Inner foveal retinal thickening was significantly greater than outer foveal retinal thickening (P < 0.0001). However, outer retinal thickening in the fovea (r = 0.644, P < 0.001), parafovea (r = 0.616, P < 0.001), and perifovea (r = 0.410, P = 0.025) was significantly correlated with visual acuity; inner retinal thickening was not. Visual acuity tended to be worse, although not significantly so, in eyes with photoreceptor disruption.

CONCLUSION

Epiretinal membrane-induced retinal damage associated with visual acuity seems to be located within the outer retina external to the inner plexiform layer.

Morphologically functional correlations of macular pathology connected with epiretinal membrane formation in spectral optical coherence tomography (SOCT)

BACKGROUND

Preretinal membrane formation is a frequently diagnosed disease in ophthalmology. Its pathogenesis is unclear. Optical coherence tomography is an important diagnostic tool in patients with epiretinal membranes. In our study we use high-speed and high-resolution spectral OCT. Our goal was to present different forms of ERM and to analyze the influence of some morphological changes on visual acuity.

METHODS

We evaluated 44 cases of preretinal fibrosis. Patients were divided into two groups depending on macula morphology. High-resolution and 3D SOCT scans were acquired from all patients and analyzed. Maximum retinal thickness and retinal thickness in the fovea were measured. Type of ERM, presence of retinal cysts and photoreceptor defects were recorded. We analyzed the influence of those data on visual acuity.

RESULTS

Globally adherent membranes were the most frequent membrane architecture type in each group. The mean visual acuity in both groups did not significantly differ. Presence of retinal cystic formation had no influence on visual acuity. A statistically significant correlation was observed between central retinal thickness and VA in Group 2 (A = -0.488; p = 0.006). Photoreceptor defect was observed in 4 patients in group 1 and 11 in group 2. Patients with photoreceptor defect had significantly lower visual acuity (P = 0.04 for Group 1 and P = 0.002 for Group 2).

CONCLUSIONS

SOCT pictures of eyes with ERM are diverse. Thanks to high-resolution and 3D scanning protocols, more information can be gathered. Morphological changes in the retina, such as oedema with cystic spaces, lamellar macular holes, macular pseudoholes and photoreceptor defects, were present in patients with ERM. Estimation of those changes may be an important prognostic factor in cases of epiretinal membranes.

ASSESSMENT OF MACULAR FUNCTION BY FOCAL ELECTRORETINOGRAM AND PATTERN ELECTRORETINOGRAM BEFORE AND AFTER EPIMACULAR MEMBRANE SURGERY

PURPOSE

To evaluate macular function before and after surgical peeling of idiopathic epimacular membrane (EMM).

METHODS

Logarithm of the minimal angle of resolution visual acuity and results of focal (central 9 x 9 degrees) electroretinogram (fERG), pattern electroretinogram (pERG), and optical coherence tomography (OCT) assessment of macular volume were evaluated for 22 eyes of 22 patients (mean age +/- SD, 63.20 +/- 10.0 years) with EMM preoperatively (baseline) and 6 months after surgical peeling. Preoperative visual acuity and fERG and pERG amplitudes observed in EMM eyes were compared with those in 15 age-matched control eyes.

RESULTS

In the preoperative evaluation, EMM eyes had a significant (P < 0.01; one-way analysis of variance) reduction in visual acuity and fERG and pERG amplitudes and an increase in OCT macular volume when compared with controls. In EMM eyes, the decrease in visual acuity was significantly correlated (P < 0.01, Pearson test) to the reduction in fERG and pERG amplitudes. At the postoperative evaluation, EMM eyes had a correlated significant (P < 0.01) increase in visual acuity, fERG amplitude, and pERG amplitude with respect to the preoperative values. All EMM eyes had a significant (P <0.01) reduction in macular volume, and retinal microanatomy was restored to normal conditions.

CONCLUSION

In EMM eyes, the decrease in visual acuity is related to dysfunction of both preganglionic (abnormal fERG) and ganglionic (abnormal pERG) macular elements. Surgical removal of EMM may induce improvement of the function of both outer and innermost macular retinal layers, leading to a related increase in visual acuity.

Surgical removal of idiopathic epiretinal membrane with or without the assistance of indocyanine green: a randomised controlled clinical trial

PURPOSE

To carry out a prospective investigation of the functional and morphological outcome of idiopathic epiretinal membrane (IEM) surgery with or without the assistance of indocyanine green (ICG) in a randomised controlled clinical trial.

METHODS

Sixty patients who underwent vitrectomy with removal of IEM combined with cataract surgery were randomly allocated to two groups: 27 patients were operated on with ICG 0.1% in glucose 5%, 33 patients without ICG. Functional outcome was assessed 3-4 months postoperatively with improvement of best-corrected visual acuity (BCVA), Amsler grid test, and automated and kinetic perimetry. Postoperative residual or recurrent IEM was assessed with bio-microscopy, and macular oedema with optical coherence tomography (OCT). Improvement in BCVA was the main outcome measure.

RESULTS

BCVA improved in 49 patients, remained unchanged in five and decreased in five. Improvement in BCVA and reduction of macular oedema were statistically significant within both groups (P < 0.01). Improvement in BCVA was not statistically significantly different whether ICG was used or not [0.17 (logarithm of minimum angle of resolution; logMAR) with ICG and 0.24 (logMAR) without ICG] (P = 0.59). There was no statistically significant difference in preoperative or postoperative BCVA, reduction of macular oedema, postoperative Amsler grid test, or incidence of residual or recurrent IEM between the two groups. Visual field defects were detected in two patients operated on with ICG.

CONCLUSIONS

Removal of IEM with or without the assistance of ICG equally improved visual function and macular morphology.

Macular function and morphology after peeling of idiopathic epiretinal membrane with and without the assistance of indocyanine green

AIM

To investigate macular function and morphology after surgical removal of idiopathic epiretinal membrane (IEM) with and without assistance of indocyanine green (ICG).

METHODS

A retrospective study as a consecutive case series, of 39 patients with IEM. 39 patients, 23 female, 16 male, mean age 67 years, underwent standard three port pars plana vitrectomy with removal of epiretinal membrane. Two groups of patients were consecutively operated: in 20 patients ICG 0.1% in glucose 5% was used to stain the epiretinal membrane. 19 patients underwent the identical procedure but without use of ICG. Postoperative follow up was 1-92 months (mean 15.5 months). Functional outcome was assessed with subjective improvement, best corrected visual acuity (BCVA), Amsler grid test, 10 degrees and 30 degrees automated perimetry (Heidelberg visual field analyser) (HFA), and Goldmann kinetic perimetry. Macular morphology was assessed with stereoscopic biomicroscopy and optical coherence tomography (OCT). The main outcome measures were macular function as determined by BCVA, presence of visual field defects, and metamorphopsia as determined by Amsler grid test, macular morphology as determined by slit lamp biomicroscopy, and OCT.

RESULTS

BCVA improved in 28 patients, remained unchanged in eight patients, and decreased in three patients. Improvement of BCVA was statistically significant in both groups (p = 0.003). Mean BCVA in patients operated with ICG improved from 0.33 preoperatively to 0.53 postoperatively. Mean BCVA in patients operated without ICG improved from 0.32 preoperatively to 0.54 postoperatively. Reduction of macular oedema as measured by OCT was statistically significant in both groups (p<0.01). There was no statistically significant difference in postoperative BCVA, macular oedema as measured by OCT, postoperative Amsler grid test, and subjective improvement between the two groups. The incidence of residual or recurrent epiretinal membrane was greater in the group operated without ICG (p = 0.014). Visual field defects were detected in one patient operated with ICG and in three patients operated without ICG.

CONCLUSIONS

Removal of epiretinal tissue with or without assistance of ICG improved visual function and reduced macular oedema in most patients. Adverse effects clearly attributable to the use of ICG were not observed but further investigation is warranted.

Évaluation de la toxicité du bleu trypan dans la chirurgie des membranes épirétiniennes idiopathiques en testant la fonction maculaire par l’électrorétinogramme multifocal

INTRODUCTION

Idiopathic epiretinal membranes are considered the consequence of glial proliferation through a defect of the internal limiting membrane and can induce a functional macular syndrome associating mainly metamorphopsia and visual acuteness. Visual disturbance is not bound to the area and the degree of transparency of the membrane, but to distortion of external layers of the retina. Multifocal electroretinography (ERGm) can assess the macular area and retina extending 20 degrees. We used this tool to study macular function pre- and post-operatively with seven patients presenting idiopathic epiretinal membrane.

PATIENT AND METHOD

All patients had successful vitrectomy, with 0.2 ml of 0.15% trypan blue (TB) staining to facilitate peeling. This stain is not toxic for the pigment epithelium but it becomes so for photoreceptors at doses exceeding 0.2%. We tried to estimate the echo of TB 0.15% on photoreceptors through this exam. An ERGm was done 1 week before the operation as well as 1 month and 4 months after on 14 eyes of seven patients with ERMs.

RESULTS

Results show a pre-operative decrease in the electrical retinal response densities in the foveal, perifoveal and parafoveal areas. One month after operation, no significant difference was found compared to pre-operative results. However, at 4 months, an improvement of the retinal response density was observed. Retinal response densities in the macular area increased progressively after ERM surgery.

CONCLUSION

The 0.15% TB facilitated ERM peeling and does not seem to present any retinal toxicity.

Optical coherence tomography and focal macular electroretinogram in eyes with epiretinal membrane and macular pseudohole

PURPOSE

To determine the morphology of macular pseudoholes (MPHs) and the relationship of morphology to macular function.

DESIGN

Observational case series.

METHODS

Optical coherence tomography (OCT) was performed on 42 eyes of 42 consecutive patients with an epiretinal membrane (ERM) and an MPH. The diameters of the MPH, and the thickness of the foveal and parafoveal retina were measured. Of these 42 eyes, focal macular electroretinograms (FMERGs) were recorded from 22 eyes of 22 patients with a 15 degree stimulus; FMERGs were also recorded with a 5 degree stimulus from 9 eyes of these 22 eyes.

RESULTS

In 42 eyes, the mean +/- Standard deviation (SD) diameter (437.7 +/- 172.8 microm) and geometrical shape of the MPHs were not significantly correlated with the visual acuity. The MPHs were divided into 2 types from the OCT images at the base of MPHs; group A had normal thickness (100-199 microm; n = 29), and group B (n = 13) had thicknesses of >or= 200 microm, or thickness < 100 microm, or irregular base. The visual acuity in group A (logarithm of the minimum angle of resolution [log MAR] mean +/- SD:.083 +/-.144) was significantly better than group B (log MAR,.407 +/-.212, P <.0001). There was a significant reduction in the amplitude of all components of FMERGs elicited by the 15 degree stimulus in the affected eyes (mean +/- SE, A-wave: 1.26 +/-.12 microv, B-wave: 3.07 +/-.27 microv, oscillatory potentials: 1.23 +/-.25 microv) compared with the normal fellow eyes (A-wave: 1.58 +/-.13 microv, B-wave: 4.14 +/-.27 microv, oscillatory potentials: 2.35 +/-.29 microv). A significant correlation was found between the relative amplitudes of the B-wave elicited by the 5 degree stimulus and the visual acuity (r =.918, P =.0005).

CONCLUSIONS

In eyes with an ERM and an MPH, the visual acuity is generally correlated with the OCT images. Macular function of eyes with an MPH resembles eyes with an ERM without an MPH. The effect of the ERM appears to be different on the base and parafovea of the MPHs.

Assessment of macular function by multifocal electroretinogram before and after epimacular membrane surgery

PURPOSE

To evaluate macular function before and after successful surgical peeling of idiopathic epimacular membranes by means of multifocal electroretinogram (ERG) and measuring the first order Kernel.

METHODS

Multifocal ERG of 10 patients (10 eyes) with idiopathic epimacular membrane were recorded before and after successful macular peeling. The retinal response densities of areas 1 and 2 were compared pre- and postoperatively and the functional state of the retina beneath the epimacular membrane was evaluated. The postoperative period was 3-6 months.

RESULTS

Preoperatively, the electrical retinal response densities in the foveal and the perifoveal area were apparently decreased. After a mean postoperative period of 3 months the electrical response densities of the above areas improved. This improvement continued 6 months after the operation.

CONCLUSION

In idiopathic epimacular membranes, the decrease in retinal electrophysiologic response was not limited to the fovea but also involved the perifoveal area. The electrical retinal response density of these areas gradually improved after peeling of the epimacular membrane.