Abstract
Objectives
To investigate the effect of internal limiting membrane peeling on vascular density of macula and optic disc in idiopathic epiretinal membrane surgery.
Methods
Thirty-six eyes of 36 patients who underwent combined phacoemulsification with intraocular lens implantation followed by pars plana vitrectomy and epiretinal membrane (ERM) removal were prospectively included in this study. Based on the intraoperative status of the internal limiting membrane (ILM) after ERM removal, the eyes were classified into two groups: The ILM-peeled group (n=22) and the ILM-unpeeled group (n=14). Vascular density of superficial capillary plexus, deep capillary plexus, optic nerve head and radial peripapillary capillary plexus were obtained by optical coherence tomography angiography before and up to 3 months after surgery
Results
After surgery, superficial capillary plexus fovea vascular density and foveal thickness decreased significantly in the internal limiting membrane unpeeled group. (p=0.016; p=0.048 respectively). There was no significant change in superficial capillary plexus paravofea (p=0.257), deep capillary plexus fovea (p=0.569), deep capillary plexus parafovea (p=0.457), optic nerve head (p=0.545) and radial peripapillary capillary plexus (p=0.975) vascular density comparison between groups.
Conclusion
Internal limiting membrane peeling has no significant effect on deep capillary plexus and the optic disc vascular density, but can reduce vascular density in the superficial capillary plexus after idiopathic epiretinal membrane peeling surgery.
Keywords: Internal limiting membrane, epiretinal membrane surgery, optical coherence tomography angiography, macula vascular density, optic disc vascular density
Introduction
Epiretinal membrane (ERM) has been termed 'preretinal macular fibrosis' or 'surface wrinkling retinopathy' in the past due to the fundus appearance resulting from contraction. It is characterized by fibrocellular proliferation on the inner retinal surface, leading to retinal distortion, macular thickening, and progressive visual impairment (1).
Pars plana vitrectomy with membrane peeling remains the standard surgical treatment for symptomatic cases, providing functional and anatomical improvement in most patients. However, the role of internal limiting membrane (ILM) peeling in ERM surgery remains controversial. While some surgeons advocate routine ILM peeling to reduce ERM recurrence and facilitate complete removal of residual tractional components, others argue that additional ILM manipulation may induce unnecessary trauma to Müller cell footplates and inner retinal layers, potentially affecting retinal function. The ILM is firmly attached to Müller cell footplates, and mechanical stress during peeling may result in Müller cell injury, potentially affecting retinal architecture and microvascular integrity (2). In addition, ILM removal may alter the biomechanical properties of the retina and lead to retinal displacement, particularly changes in the position and configuration of the foveal region (3). Alterations in retinal nerve fiber layer thickness, including transient postoperative thickening followed by subsequent thinning, have also been reported after ILM peeling and are thought to reflect Müller cell dysfunction and inner retinal remodeling (4). Consequently, whether ILM peeling provides additional microstructural or functional benefit beyond ERM removal alone is still debated in the literature.
Optical coherence tomography angiography (OCT-A), a non-invasive method with erythrocyte motion detection technology, can evaluate retinal microvasculature segmentally and quantitatively using a novel algorithm. These properties, make it a very suitable method for evaluating the effect of ERM on retinal microvasculature (5). Although previous OCT-A studies have evaluated vascular changes after ERM surgery, the specific contribution of ILM peeling to macular and optic disc microvascular remodeling remains unclear. Therefore, we aimed to evaluate the effects of ILM peeling on macular and optic disc microvascular parameters using OCT-A.
Methods
This prospective, nonrandomized, interventional study was approved by the clinical research ethics committee of Kahramanmaraş Sütçü İmam University Faculty of Medicine (Ethics committee date: 16.10.2019, decision number: 2019/18/10, approval number: 312. It was not prospectively registered in a clinical trial registry). Written informed consent in accordance with the Declaration of Helsinki was obtained from all participants. Thirty-six eyes of 36 patients who underwent pars plana vitrectomy (PPV) by a single surgeon for symptomatic idiopathic ERM were evaluated.
Participants
Only idiopathic ERMs were included in the study. ERM was secondary to other ocular diseases or previous intraocular surgery; patients using chronic ocular drugs or with optic disc pathology were excluded. Epiretinal membranes were graded according to the optical coherence tomography-based Govetto classification. Only patients with stage 2 or stage 3 idiopathic ERM were included in the study. Other exclusion criteria were severe media opacity, undetectable foveal localization due to severe contraction. OCT-A images were reviewed before analysis regarding image quality, acquisition artifacts, and segmentation accuracy. Scans with a signal strength index below 50% and cases with significant segmentation errors that could affect vascular density measurements were excluded. Vascular density parameters were obtained from the automated segmentation analysis provided by the OCT-A device software. OCT-A was performed after a complete ophthalmologic examination at preoperative and 1st week, 1st month, and 3rd month after surgery. Best-corrected visual acuity (BCVA) was recorded using the Snellen chart as part of routine clinical evaluation. Since visual acuity was not a study outcome Snellen values were not converted to logMAR.
Optical coherence tomography angiography protocol
Angiographic images were obtained with OCT-A (RTVue; Optovue Inc. Fremont, CA, USA). Superficial capillary plexus (SCP), deep capillary plexus (DCP), Optic nerve head (ONH), Radial peripapillary capillar plexus (RPCP), and retinal thickness were automatically segmented by the software. Fovea-centered (6x6 mm angio-retina) image was obtained for macular angioanalysis. Macular angioanalysis and retinal thickness data were automatically calculated from the fovea-centered Early Treatment Diabetic Retinopathy Study (ETDRS) grid (3mm diameter, central 1 mm fovea, peripheral 2 mm parafovea ) (Fig. 1A). Vascular density (VD) was quantified by the percentage of vascular area in the selected area. The image (4.5x 4.5 mm angio-disc ) was obtained for optic disc angioanalysis. Optic disc data were calculated from an automatically determined ring 750 μm wider than the edges of the optical disc (Fig. 1B). The percentage of vascular area in this 750 μm-thick elliptical ring corresponding to the peripapillary region was quantified as peripapillary VD.
Figure 1.
Automatic measurement of macula and optic disc vascularl density with optic coherence tomograpfhy angiography. (A) Macular angioanalysis and retinal thickness data were automatically calculated from the fovea-centered Early Treatment Diabetic Retinopathy Study (ETDRS) grid (3mm diameter, central 1 mm fovea, peripheral 2 mm parafovea ). Vascular density was quantified by the percentage of vascular area in the selected area. (B) Optic disc data were calculated from an automatically determined ring 750 μm wider than the edges of the optical disc. The percentage of vascular area in this 750 μm-thick elliptical ring corresponding to the peripapillary region was quantified as peripapillary vascular density.
Surgical technique
All participants underwent phacoemulsification and intraocular lens implantation with the Centurion-Vision System (Alcon Laboratories, Inc. Texas, USA) device. Surgery continued with a 3-port 23-gauge transconjunctival sutureless PPV with an EVA phaco-vitrectomy system (DORC, The Netherlands) device. The ERM and ILM were stained with Mebrane-Blue-Dual (DORC, The Netherlands) dye and were peeled with 23-Gauge Eckardt end-gripping intraocular microforceps (DORC, The Netherlands).
After ERM removal, the integrity of the underlying ILM was routinely assessed under staining with Membrane Blue Dual. Eyes were categorized according to whether the ILM remained intact (14 patients) or was removed together with the ERM. Cases with uncertain ILM status were excluded. If the ILM was peeled, ILM peeling was performed in a standardized manner with an intended diameter of approximately 1500 μm centered on the fovea (22 patients). The surgery was completed without the use of buffering material.
Primary outcomes were the change in retinal microvascular parameters measured by OCT-A, particularly vessel density changes in the SCP and DCP and in optic disc after surgery. Other OCT and OCT-A parameters have been considered secondary outcomes.
Statistical analysis
Statistical analysis was performed with SPSS software version 20.0 (SPSS Inc, Chicago, USA). Continuous variables are shown as mean ±standard deviation (SD), (minimum-maximum), and numbers for categorical variables. Pearson Chi-square test was used for categorical variables and the independent sample T-test was used for continuous variables in comparison of demographic data. The normal distribution of repeated measurements was checked with the Shapiro-Wilk test and the kurtosis and skewness values.
Repeated measurements within the ILM peeled or ILM unpeeled group were analyzed with repeated analysis of variance ANOVA. Pairwise comparisons were presented with Bonferroni correction. Although p values of repeated analysis of variance ANOVA are presented as standard in the tables, only values that reached statistical significance were shown for pairwise comparisons. The differences between the first measurement and the last measurement of ILM peeled and ILM unpeeled groups were compared with an independent sample t-test. Analysis of differences was used to compare ILM peeled and ILM unpeeled groups. P value <0.05 was considered statistically significant.
Results
There was no statistically significant difference between the groups in terms of age and gender (Table 1).
Table 1.
Demographic characteristics of study groups
| ILM peeled (n=22) | ILM Unpeeled (n=14) | p | |
|---|---|---|---|
| Age, year mean±SD (min-max) | 66.8±7.1 (50-76) | 71.5±7.1 (61-89) | 0.063* |
| Gender n (%) | |||
| Male | 14 (63.6) | 10 (71.4) | 0.727** |
| Female | 8 (36.4) | 4 (28.6) |
All data are presented as the means ± SD,(min-max). SD: standart deviation Min: minimum Max: maximum ILM: internal limiting membrane. * Independent sample T-test ** Pearson Chi-square test.
Macular angioanalysis is shown in Table 2. SCP and DCP fovea VD were not significantly changed in the ILM peeled group (p=0.989; p=0.095 respectively). In the ILM unpeeled group, SCP fovea VD decreased significantly in the postoperative 3rd month compared to preoperative (p=0.025). This significant decrease in subgroup analysis was also significant when comparing between groups (p=0.016). Although parafovea VD showed a transient decrease in subgroup analysis at 1 week in the ILM peeled group, both SCP and DCP parafovea VD changes were not significant in comparison between groups (p=0.257; p=0.457, respectively).
Table 2.
Macular angioanalysis
| Preoperative | Postoperative | p | |||||
|---|---|---|---|---|---|---|---|
| 1.Week | 1. Month | 3. Month | Within Group (a) | Pairwise Subgroup (b) | Between Groups (c) | ||
| SCP Fovea VD (%) | |||||||
| ILM Peeled | 35.79±6.08 (20.84-44.54) | 37.30±4.87 (29.38-44.74) | 36.93±5.18 (28.64-46.57) | 37.91±5.87 (25.78-46.77) | 0.989 | 0.016 | |
| ILM Unpeeled | 38.90±6.53 (28.54-54.72) | 33.77±5.12 (26.96-43.41) | 32.31±6.28 (26.72-48.40) | 30.61±4.87 (23.65-40.00) | 0.008 | (preop-1.week) 0.040 (preop-1.month) 0.031 (preop-3.month) 0.025 | |
| DCP Fovea VD (%) | |||||||
| ILM Peeled | 34.17±8.87 (15.85-48.79) | 40.17±6.33 (30.27-51.26) | 35.93±7.32 (16.10-48.84) | 34.97±7.66 (18.67-46.91) | 0.095 | 0.569 | |
| ILM Unpeeled | 30.16±11.21 (7.60-48.30) | 29.83±8.37 (12.59-40.79) | 30.40±5.87 (19.65-39.75) | 30.47±6.66 (21.33-43.41) | 0.695 | ||
| SCP Parafovea VD (%) | |||||||
| ILM Peeled | 44.13±3.84 (37.77-53.81) | 42.76±3.04 (36.12-46.84) | 44.13±4.76 (35.12-52.65) | 45.53±4.99 (34.01-52.52) | 0.002 | (preop-1.week) 0.030 (1.week-3.month) <0.001 | 0.257 |
| ILM Unpeeled | 41.80±6.01 (33.49-52.62) | 42.62±4.95 (35.09-46.16) | 44.46±4.86 (35.35-51.48) | 44.58±7.55 (31.67-55.65) | 0.109 | ||
| DCP Parafovea VD (%) | |||||||
| ILM Peeled | 50.49±4.54 (39.16-58.29) | 48.19±5.15 (40.27-57.32) | 50.42±4.93 (42.07-60.52) | 52.01±5.53 (41.82-60.07) | <0.001 | (preop-1.week) 0.026 (1.week-1.month) 0.011 (1.week-3.month) 0.009 | 0.457 |
| ILM Unpeeled | 45.65±7.06 (30.27-56.91) | 46.56±7.05 (35.49-57.83) | 48.48±6.55 (37.74-56.24) | 50.18±5.27 (43.45-61.88) | 0.419 | ||
All data are presented as the means ± SD,(min-max). SD: standart deviation Min: minimum, Max: maximum, SCP: superficial capillary plexus, DCP: deep capillary plexus, ILM: internal limiting membrane,VD: vascular density, Preop: preoperative. (a) General linear model analysis of repeated measures (ANOVA) within each study group. (b) In pairwise comparison of subgroups, only values with p<0.05 are shown in subgroup analysis. (c) Comparison of the difference between the first measurement and the last measurement between ILM peeled and ILM unpeeled groups with independent sample t-test.
Retinal thickness parameters are shown in Table 3. Foveal thickness did not change significantly in the ILM peeled group (p=0.331). In the ILM unpeeled group, foveal thickness reduced significantly in the postoperative 3rd month compared to the preoperative level (p=0.012). This significant reduction in pairwise subgroup analysis was also significant in comparison between groups (p=0.048). Parafoveal thickness was significantly reduced in both groups at 3 months postoperatively, ILM peeled (p=0.050) and unpeeled (p=0.030). However, the reduction levels were similar in both groups (p=0.968).
Table 3.
Comparison of retinal thickness within groups, subgroups, and between groups
| Preoperative | Postoperative | p | |||||
|---|---|---|---|---|---|---|---|
| 1.Week | 1. Month | 3. Month | Within Group (a) | Pairwise Subgroup (b) | Between Groups (c) | ||
| Fovea thickness (μm) | |||||||
| ILM Peeled | 422±86 (297-614) |
412±56 (315-527) |
411±49 (334-500) |
394±58 (323-498) |
0.331 | 0.048 | |
| ILM Unpeeled | 437±85 (309-594) |
379±82 (280-503) |
358±77 (251-506) |
348±88 (189-501) |
0.001 | (preop-1.week) 0.009 (preop-1.month) 0.003 (preop-3.month) 0.012 (1.month-3.month) 0.047 | |
| Parafovea thickness (μm) | |||||||
| ILM Peeled | 398±56 (336-543) |
385±28 (343-457) |
374±24 (337-429) |
360±32 (304-413) |
0.011 | (preop-3.month) 0.050 (1.week-3.month) 0.036 (1.month-3.month 0.018 | 0.968 |
| ILM Unpeeled | 402±58 (321-537) |
374±53 (301-492) |
367±49 (288-453) |
365±45 (281-455) |
0.014 | (preop-1.week) 0.011 (preop-1.month) 0.010 (preop-3.month) 0.030 | |
| Inner retinal thickness (μm) | |||||||
| ILM Peeled | 153±10 (135-167) |
160±10 (143-173) |
147±13 (121-167) |
137±19 (98-166) |
<0.001 | (preop-1.month) 0.018 (preop-3.month) 0.001 (1.week-1.month) 0.006 (1.week-3.month) 0.030 (1.month-3.month) 0.030 | 0.419 |
| ILM Unpeeled | 151±1 (105-172) |
149±1 (105-171) |
140±19 (106-166) |
141±20 (99-166) |
0.230 | ||
All data are presented as the means ± SD, (min-max). SD: standart deviation Min: minimum, Max: maximum, μm: mikrometer, ILM: internal limiting membrane Preop: preoperative. (a) General linear model analysis of repeated measures within each study group. (b) In pairwise comparison of subgroups, only values with p<0.05 are shown in subgroup analysis. (c) Comparison of the difference between the first measurement and the last measurement between ILM peeled and ILM unpeeled groups with independent sample t-test.
Inner retinal thickness did not change significantly in the ILM unpeeled group (p=0.230). In the ILM peeled group, inner retinal thickness increased in the 1st week and then progressively thinned, in the postoperative 3rd month compared to preoperative thickness (p=0.001). However, this significant thinning in the subgroup analysis was not significant in comparison between groups (p=0.419).
Optic disc angioanalysis is shown in Table 4. Peripapillary VD showed a similar course in both groups, decreasing in the first week and then increasing again. Although this decrease in the 1st week could reach significant levels in the ILM peeled group, no significant difference was found between the preoperative and postoperative 3rd month in pairwise subgroup analysis. VD changes were not significant in comparison between groups in ONH (p=0.545) and RPCP (p=0.975).
Table 4.
Optic disc angioanalysis
| Preoperative | Postoperative | p | |||||
|---|---|---|---|---|---|---|---|
| 1.Week | 1. Month | 3. Month | Within Group (a) | Pairwise Subgroup (b) | Between Groups (c) | ||
| ONH Peripapillary VD (%) | |||||||
| ILM Peeled | 57.71±4.17 (48.93-64.04) |
51.96±4.88 (39.36-58.48) |
54.76±4.20 (44.94-62.33) |
56.39±4.13 (44.26-63.89) |
<0.001 | (preop-1.week) 0.015 (1.week-1.month) 0.012 (1.week-3.month) 0.001 |
0.545 |
| ILM Unpeeled | 53.56±6.13 (37.01-60.67) |
51.90±6.65 (36.27-60.81) |
54.49±4.70 (47.50-60.63) |
55.51±4.89 (43.81-62.03) |
0.115 | ||
| RPCP Peripapillary VD (%) | |||||||
| ILM Peeled | 58.30±5.18 (43.04-66.82) |
52.46±6.57 (34.36-64.02) |
54.65±5.32 (40.53-60.65) |
56.60±6.20 (39.27-64.57) |
<0.001 | (preop-1.week) <0.001 (preop-1.month) 0.017 (1.week-1.month) 0.008 (1.week-3.month) 0.001 (1.month-3.month) 0.019 |
0.975 |
| ILM Unpeeled | 54.25±7.18 (32.87-61.95) |
50.98±7.11 (32.90-59.08) |
54.16±4.76 (43.10-60.80) |
55.93±4.71 (43.33-60.03) |
0.079 | ||
All data are presented as the means ± SD, min-max). SD: standart deviation Min: minimum, Max: maximum, ONH: optic nerve head RPCP: radial peripapillary capillary plexus ILM: internal limiting membrane VD: vascular density Preop: preoperative. (a) General linear model analysis of repeated measures within each study group. (b) In pairwise comparison of subgroups, only values with p<0.05 are shown in subgroup analysis. (c) Comparison of the difference between the first measurement and the last measurement between ILM peeled and ILM unpeeled groups with independent sample t-test.
BCVA increased significantly in both groups at 3 months postoperatively, ILM peeled (p=0.006) and unpeeled (p=0.042). However, the level of increase in BCVA was not significant in the comparison between groups (p=0.768) (Table 5).
Table 5.
Comparison of visual acuity within groups, subgroups, and between groups
| Preoperative | Postoperative | p | |||||
|---|---|---|---|---|---|---|---|
| 1.Week | 1. Month | 3. Month | Within Group (a) | Pairwise Subgroup (b) | Between Groups (c) | ||
| BCVA, Snellen | |||||||
| ILM Peeled | 0.29±0.10 (0.10-0.50) |
0.29±0.14 (0.10-0.70) |
0.34±0.15 (0.05-0.60) |
0.44±0.21 (0.05-0.80) |
<0.001 | (preop-1.month) 0.045 (preop-3.month) 0.002 (1.week-3month) 0.008 | 0.976 |
| ILM Unpeeled | 0.21±0.10 (0.05-0.40) |
0.22±0.12 (0.05-0.4) |
0.30±0.15 (0.05-0.60) |
0.38±0.19 (0.05-0.70) |
0.001 | (preop-3.month) 0.030 | |
All data are presented as the means ± SD, (min-max). SD: standart deviation Min: minimum, Max: maximum, BCVA: best corrected visual acuity ILM: internal limiting membrane VD: vascular density Preop: preoperative (a) General linear model analysis of repeated measures within each study group. (b) In pairwise comparison of subgroups, only values with p<0.05 are shown in subgroup analysis. (c) Comparison of the difference between the first measurement and the last measurement between ILM peeled and ILM nonpeled groups with independent sample t-test.
Discussion
Centripetal contraction of the ERM drags vascular structures topographically toward the fovea (6-12). Although ERM peeling should theoretically shift vascularity from the fovea to the periphery, topographic change is not the only parameter affecting vascular density. There are functional changes such as recanalization and improvement in vascular tortuosity and occlusions with the relaxation of centripetal contraction (12,13). Another parameter that will affect the change in the OCT-A parameter is the ERM grade (8). For these reasons, OCT-A studies report conflicting results.
Chen et al. (10) reported the expansion of the foveal avascular zone (FAZ), a decrease in fovea VD, and an increase in parafovea VD in SCP and DCP after ERM peeling. The author explained these results of vascular density normalization by the relaxation of centripetal traction. However, there are also different OCT-A studies indicating that there is no significant change in total retinal perfusion , fovea VD , or FAZ after ERM peeling (11,14-16). Some authors associate centripetal contraction that persists after ERM removal with ILM peeling (6,16,17). Although these mentioned studies did not have an ILM unpeeling group, they can provide insight into ILM peeling. In our study, foveaVD and parafoveaVD did not change in the ILM peeling group. This may reflect the balancing of the centrifugal effect caused by ERM peeling with the centripetal effect caused by ILM peeling.
When OCT-A studies comparing ILM peeling and unpeeling groups in ERM surgery were reviewed; Ericek et al. (18) reported that there was no significant change in FAZ, flow, and Parafoveal VD after surgery in both groups. The authors suggested that the effect of surgery on microvascular structures was limited. In the study of Muller et al. (19) , the results regarding the macular microvasculature demonstrated no difference with peeling of the ILM. Another similar study revealed that the retinal vascular tortuosity index and fovea VD after ERM surgery were similar in eyes with and without ILM peeling, and the authors suggested that ILM peeling had no additional effect on microvascular traction (20). Contrary to these studies, Kumagai et al. (3) demonstrated the centripetal movement caused by ILM peeling by comparing OCT-A with and without ILM peeling. They explained the centripetal movement that occurs after ILM peeling by the structural change in Müller cells that stretch the fovea centrifugally. We observed both SCP fovea VD and the foveal thickness significantly decreased in the ILM unpeeled group in our study, reflecting the centrifugal movement and foveal pit remodeling. In the study of Gabriel et al. (21) the change in FAZ and parafoveal VD was greater in the ILM unpeeled group than in the ILM peeled group. The authors emphasized that microvascular remodeling was more pronounced in the ILM unpeeled group. Similar to this study, although significant microvascular changes were observed in the ILM unpeeled group we did not observe any significant microvascular changes in the ILM peeled group when compared to the preoperative and postoperative 3rd month. Li et al. (22) reported in their study on diabetic ERMs that ILM peeling delayed the improvement in DCP vascular parameters. However, we did not observe any significant change in DCP in either the ILM peeled or ILM unpeeled groups. On the contrary, there was a significant change in SCP in our study. The different results may be related to our participants having idiopathic ERM not diabetic.
In the subgroup analysis of the ILM peeled group, the inner retinal thickness tended to increase at week 1, but significant thinning was observed at the 3rd-month measurement. In the ILM unpeeled group, no change was observed in the inner retinal thickness over time. As it is known, the earliest change in the retina caused by ILM peeling is retinal nerve fiber layer (RNFL) edema. Edema can be detected as early as 1 week and completely regresses within 3 months (23,24). Following the resolution of edema, thinning can be observed in the inner retina (24,25). Although it could not reach a significant level between groups, our inner retinal thickness result in subgroup analysis is consistent with the literature.
To the best of our knowledge, there are not OCT-A studies in the literature comparing the optic disc VD parameters of eyes with and without ILM peeling in patients with ERM. Kumagai et al. studied papilla-foveal distance and FAZ with OCT-A but not VD. After ILM peeling, the fovea is displaced towards the optic disc in their study (3). Yoon et al. (26) peeled the ERM and ILM in all cases. The authors suggested that ILM peeling caused microvascular damage starting from the inferior sector in the peripapillary VD. Contrary to this study change in vascular parameters of the optic disc was temporary in our study. Peripapillary VD of ONH and RPCP decreased in both groups at week 1. Although this decrease reached a significant level in the ILM peeled group, the parameters increased again to the baseline level, thus there was no significant difference between the first and the last measurement in both groups. As a result of the effects of some factors affecting optic discs, such as mechanical trauma caused by intraocular fluid movement or vitreous detachment during surgery, dyes used in visualization, or surgical inflammation; transient diffuse peripapillary RNFL edema develops in the early postoperative period (23). The similar course in both groups in our study suggests that the reduction in optic disc parameters at week 1 may be related to factors induced by surgery as mentioned above, rather than ILM peeling.
Lee and Kim showed that foveal contour formation was more frequent and the fovea was thinner in the eyes without ILM peeling. Visual results were similar in eyes with and without ILM peeling in their study (27). Supporting this we observed a thinner fovea in the ILM unpeeled group and we attributed this to centripetal motion. Also similarly the increase in BCVA did not affect ILM peeling in our study. Özdek et al. (28) showed that the improvement in foveal anatomy and the decrease in foveal thickness were slower in eyes with ILM peeling in the first postoperative year, but there was no significant difference in foveal thickness and anatomy between eyes with and without ILM peeling at the end of 2 years. Although our follow-up period was 3 months, the main outcome measure in our study was vascular parameters, and the decrease in foveal thickness is only supported to explain the centrifugal movement after ILM preservation.
Our study have some limitations. An important limitation of this study is the non-randomized allocation of groups. Since ILM peeling status was determined intraoperatively according to the presence or absence of spontaneous ILM separation after ERM removal, the groups may differ regarding underlying ERM biological characteristics. Eyes with spontaneous ILM separation may have stronger ERM–ILM adhesion, which could independently affect postoperative retinal microvascular parameters. Therefore, the observed findings should be interpreted cautiously, as differences between groups may reflect both the effects of ILM peeling and intrinsic biological differences in ERM characteristics. Although ERM grading was performed according to the Govetto classification, the relatively small sample size prevented subgroup analysis according to ERM stage. Future studies with larger populations may further clarify whether the effects of ILM peeling on retinal microvascular remodeling differ according to ERM severity. Our follow-up period was 3 months. There is a study suggesting that recanalization continues for up to one year (13). Although our 3-month follow-up period was sufficient to evaluate early postoperative microvascular changes, longer follow-up may be required to assess the complete course of retinal vascular remodeling and anatomical displacement after ERM surgery. Future studies with longer observation periods are needed to clarify the long-term influence of ILM peeling on retinal microvascular changes. There is also a study that shows functional and anatomical recovery are similar in the long term, as mentioned above (28). The relatively small sample size is an important limitation of this study. Although the prospective design and standardized surgical approach strengthen the findings, the study may have limited power to detect small differences between groups. Therefore, non-significant between-group findings should be interpreted cautiously and do not necessarily exclude the possibility of clinically relevant differences. However, the number of OCT-A studies comparing eyes with and without ILM peeling in the treatment of ERM is very few (3,18-22). Among these studies, our study is the second with the largest sample size and the only study that evaluated optic disc VD and macular VD parameters together in the same eye. OCT-A vascular density measurements should be interpreted with caution, as they represent the proportion of detectable vascular signals within a defined area rather than direct measurements of blood flow, retinal perfusion, or oxygen delivery. Therefore, changes in vascular density observed in our study may reflect alterations in retinal vascular architecture or detectable flow signals rather than absolute changes in retinal circulation. Another limitation of this study is that all patients underwent combined phacoemulsification and intraocular lens implantation before vitrectomy. Cataract surgery itself may influence retinal thickness measurements, retinal perfusion parameters, and OCT-A image quality. Since a vitrectomy-only control group was not included, the individual contributions of cataract surgery, ERM removal, and ILM peeling to postoperative structural and vascular changes cannot be completely separated. Therefore, our findings should be interpreted as reflecting the combined effects of these surgical interventions rather than the isolated effect of ILM peeling. Given the exploratory nature of several secondary analyses and the number of evaluated OCT and OCT-A parameters, the possibility of type I error due to multiple comparisons should be considered when interpreting the results.
Conclusion
In conclusion, our results suggest that ILM peeling may influence SCP vascular remodeling after ERM removal by counterbalancing the tractional effects associated with ERM peeling. No statistically significant effect of ILM peeling on DCP or optic disc vascular density was detected within the 3-month follow-up period. Larger studies with longer follow-up are required to better elucidate the long-term effects of ILM peeling on retinal microvascular remodeling.
Footnotes
How to cite this article: Evgin I, Guler M, Kokusari G. Effect of Internal Limiting Membrane Peeling on Macular and Optic Disc Vascular Density Following Epiretinal Membrane Surgery. Beyoglu Eye J 2026; 11(3): XX-XX
Disclosures
Ethics Committee Approval
This study was approved by the clinical research ethics committee of Kahramanmaraş Sütçü İmam University Faculty of Medicine (Date: 16.10.2019, No: 2019/18/10, clinical trial registration number: 312).
Informed Consent
Written informed consent in accordance with the Declaration of Helsinki was obtained from all participants
Conflict of Interest
All authors declare that they have no conflicts of interest.
Funding
None
Use of AI for Writing Assistance
Not declared.
Author Contributions
Concept – I.E., M.G., G.K.; Design – I.E., M.G., G.K.; Supervision – I.E., M.G., G.K.; Resource – I.E., M.G., G.K.; Materials – I.E., M.G., G.K.; Data Collection and/or Processing – I.E., M.G., G.K.; Analysis and/or Interpretation – I.E., M.G., G.K.; Literature Search – I.E., M.G., G.K.; Writing – I.E., M.G., G.K; Critical Reviews – I.E., M.G., G.K.
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