**4. Epiretinal membrane and internal limiting membrane peeling**

The aim of surgery is to remove tractions caused by ERM and ectopic inner foveal layers. Three-port pars plana vitrectomy followed by an ERM peeling, using 23-, 25-, or 26-gauge instruments is the standard of care. The use of smaller gauges allows for a faster surgery recovery [39].

Since the separation of the ILM has been shown to be compatible with a good visual function [40–42], intentional removal of the ILM has been performed in order to increase macula elasticity, which could be beneficial for treating several macular disorders, such as macular holes, chronic diabetic macular edema, vitreomacular traction, and myopic foveschisis [28, 29]. Removal of the macular ILM has been demonstrated to greatly improve the anatomical success rate of the surgical treatment of macular holes [43, 44].

The ILM is suspected to provide a scaffold for cellular proliferation and its active peeling has become a common practice during ERM removal. Simultaneous ILM peel is a frequent occurrence during ERM surgery when there is a complete ERM macula adhesion on OCT [45].

Postoperative recurrence of epiretinal membrane range from 10 to 21%. Specimens of recurrent ERM evaluated by electron microscopic demonstrate mainly myofibroblasts, but also fibrocytes, retinal pigment cells, fragments of ILM, and new collagen [45, 46]. Also, some studies had demonstrated remnants of ERM or cell remnants on ILM vitreous surface specimens [47–49].

Thus, ILM peeling combined with ERM removal has been performed in an attempt to remove cells from the retina surface that would serve as potential sites for ERM reproliferation [50].

*Internal Limiting Membrane Peeling in Idiopathic Epiretinal Membrane DOI: http://dx.doi.org/10.5772/intechopen.108772*

Chromovitrectomy is frequently used as an adjuvant to facilitate ILM identification. It involves the use of dyes intended to improve ERM and ILM visibility. Trypan blue (TB), brilliant blue G (BBG), and indocyanine green (ICG) are the most frequently used dyes.

Trypan blue stains mainly the ERM while BBG stains mainly the ILM. ICG is an excellent dye for ILM stain, although it has significant evidence of retina and optic nerve toxicity [51, 52].

Despite its toxicity evidence, ICG is still used since it has been described to facilitate ILM peeling by adding an ILM stiffening effect through a collagen IV crosslinking [53] and also having a higher ILM staining property than BBG [54].

A thicker and stiffer ILM facilitates surgical removal and according to previously described, a region within a foveal distance of roughly 1000 μm would be ideal for starting the peeling. Also, in this region, a better stain during chromovitrectomy is expected [27].

The use of BBG has been proven helpful in better visualizing ILM and decreasing ERM fragments, which may be the source of recurrent ERMs [55].

### **5. Updated data on maintaining ILM versus ILM peeling in ERM treatment**

Even more than 10 years after additional ILM peeling has been introduced, there is still a discussion of the best surgical approach for ERM treatment in order to prevent its recurrence.

Some studies showed that ILM peeling prevented ERM recurrence [48, 56, 57]. According to those studies, groups that had ILM peeling had no recurrence of ERM, while in groups where double peeling was not performed, the recurrence reached 17,6%.

On contrary, some other studies showed that patients who had ERM peeling without removing the ILM had an even better anatomical and visual outcome [58–60].

Ahn et al. [60] compared the OCT postoperative status and visual acuity after ERM removal with or without additional ILM peeling. They found that patients who had epiretinal membrane surgery with additional ILM peeling showed worse visual acuity and most severe cone outer segment tips and inner and outer segment junction line defects. Those photoreceptors defects were gradually restored at 12 months postoperatively. A possible reason for this finding is that by removing the ILM, the footplates of Muller cells are also being removed, leading to mechanical and functional damage to those important cells.

There is a supposition that ILM peeling spares the ganglion cells and is limited to the Müller cell footplates. Some studies have suggested that injury to Müller cells was due to direct and indirect traumas, caused by surgical instruments and traction during membrane removal, respectively [61–63].

Deltour et al. [64], in a retrospective study, demonstrated that active peeling induces more numerous and deeper microscotomas than spontaneous peeling. Later, a prospective, randomized, controlled, single-blind, multicentered trial with two parallel arms investigated differences between active ILM peeling and passive ILM peeling, and showed similar findings [65].

A recent meta-analysis of randomized and controlled trials showed no statistically significant difference in final visual acuity and recurrence rate of ERM when ILM peeling was performed. As for the central macular thickness (CMT), it was thicker within 6 months postoperatively in those patients who had additional ILM peeling.

#### **Figure 3.**

*DONFL after double peeling for stage 4 ERM. a. Enface OCT showing numerous dark areas corresponding to retinal cavitations. b. B scan OCT showing increased foveal thickness due to hyporeflective spaces—images shared by Michelle Gantois, MD.*

A possible reason for a thicker CMT in a combined ERM and ILM peeling is that it could induce retinal edema. Also, this meta-analysis data showed that ILM peeling seemed to result in more complications, including intraoperative retinal breaks and nonarteritic anterior ischemic optic neuropathy [66].

Distinct spectral domain optical coherence tomography (SD-OCT) findings on the inner retina have been associated with ILM peeling. Swelling of the arcuate fiber layer (SANFL) is an earlier pathology that is characterized on B scan OCT as hyperreflective images and on infrared as hyperfluorescent arcuate areas. SANFL is followed by dissociated optic nerve fiber layer defect (DONFL) [67]. DONFL (**Figure 3**) presents on SD-OCT as irregular depressions in the nerve fiber layer due to thinning of the ganglion cell layer [67, 68] and more visible with shorter wavelength illumination [69, 70]. It is thought to be due to trauma to Muller cells after the ILM is peeled, disconnecting their attached foot plates [62, 70, 71], and exposing the retinal nerve fiber layers. Trauma to Muller footplates would possibly result in changes in the bundling of the nerve fiber layer and also a volume reduction in the ganglion cell layer where the Muller cell bodies are located [72].

It also had been reported that (DONFL) would also cause a reduction in central retinal sensitivity and paracentral scotomas. Terasaki et al. also reported a delayed recovery of the b-wave amplitude of the focal macula electroretinogram after ILM peeling during macular hole surgery [73].

It is still unclear the cause of DONFL development, but it has been also associated with surgical trauma during ILM peeling [74].

#### **6. Conclusion**

The surgical procedures for removing ERM are well-established and safe. However, there is still not enough data to affirm if an additional ILM peeling is always an important surgical step or would be better to be performed only in selected ERM cases.

There are proven morphological and functional retina modifications with an additional ILM peeling, although is not known whether those changes could cause progressive retinal damage in the medium or long term.

In my own experience, recurrence rates of ERM are not common, even when ILM is not removed. And since ILM peeling can lead to complications, in my point of view, it is not essential, unless when associated with macular holes. In addition, ILM removal could also be needed when epiretinal proliferation is present under the *Internal Limiting Membrane Peeling in Idiopathic Epiretinal Membrane DOI: http://dx.doi.org/10.5772/intechopen.108772*

ERM. Evaluation of ILM status after removal of ERM is also important to decide if it is worth to removed.

Intraoperative optical coherence tomography is an emerging technology that has been evolving and improving in reproducibility and motion artifacts. Soon it will help guide decision-making in the surgical approach for treating ERM, including better visualization of debris left on the retina surface that needs to be removed, as well as when ILM should not be left in place.
