ILM peeling prevents development of ERMs
Only 2% of patients with internal limiting membrane peeling developed an epiretinal membrane compared with 46% with no peeling.
Peeling of internal limiting membranes (ILMs) seems to prevent development of epiretinal membranes (ERMs) following vitrectomy to treat primary rhegmatogenous retinal detachments (RRDs), and based on findings on optical coherence tomography (OCT) images, three types of ERMs were identified, which may improve the criteria used to establish the surgical indications for and timing of ERM removal.
The rates of development of ERMs after vitrectomy to repair primary RRDs is not rare and have been reported to range from 9% to 34%.1-5 The ERMs may require another vitrectomy because of visual loss and metamorphopsia. Because of the absence of a well-defined classification system, the true incidence of ERMs is unknown. So, a new classification would fill a gap in treatment criteria, because as Luis Arias, PhD, and colleagues pointed out, there currently are no established uniform criteria.
In light of that, the investigators conducted a prospective comparative case series with the primary aim of determining if ILM peeling prevents the development of ERMs after primary vitrectomy performed to treat RRDs. The investigators also sought to establish a new classification system for ERMs that develop postoperatively.
The study included 140 consecutive eyes of 140 patients with a primary RRD that underwent surgery performed by 1 surgeon. The patients were divided into two groups, i.e., 70 patients each in the ILM peeling and non-peeling groups. Swept-source OCT (SS-OCT) was performed to identify ERMs postoperatively.
Results
Arias reported that an ERM developed in 26 (46.4%) eyes in the ILM nonpeeling group and 1 eye (1.8%) in the ILM peeling group, a difference that reached significance (p ⩽ 0.001). The median visual acuity (VA) improved in both groups; at the final examination, the median Snellen VA was 20/25 in the ILM peeling group and 20/20 in the nonpeeling group.
SS-OCT identified 3 different types of ERMs. Type 1 was described as a highly epimacular reflective band without other relevant alterations. Type 2 also was described as a highly epimacular reflective band with thickening of the inner retinal layers; type 2 ERMs may also present inner retinal surface wrinkling and superficial retinal plexus deformation on OCT angiography and en face images. Type 3 was described as a highly epimacular reflective band with thickening of the inner retinal layers and superficial retinal plexus deformation on OCT angiography and en face images; other alterations seen in type 3 included outer retinal nuclear layer thickening and intraretinal cysts. The authors reported their findings in Retina.6
Analysis of the 3 types of ERMs showed that while all presented as a highly epimacular reflective band, the inner retinal layer thickening differed among the 3, with higher percentages of thickening in types 2 and 3. Other differences were the outer nuclear layer thickening and the presence of intraretinal cysts, which were more common in type 3 ERMs.
Superficial retinal plexus deformations on OCTA and en face images were seen in 100% of type 3 ERMs, 41.6% of type 2 ERMs, and none of type 1 ERMs. It was noteworthy, according to the investigators, that all patients with these deformations also had metamorphopsia.
The central retinal thicknesses (CRTs) differed among the ERM types. The CRTs in type 1 ERMS differed significantly between types 2 and 3 (p = 0.017 and p < 0.001, respectively) but not between types 2 and 3. The VAs differed significantly (p < 0.001) between types 1 and 3 but not between types 1 and 2 and types 2 and 3.
“Of the 26 ERMs in the nonpeeling group, 7 (26.9%) were classified as type 1, 12 (46.1%) as type 2, and 7 (26.9%) type 3,” Dr. Arias said. Surgery was indicated in 12 eyes with ERMs because of decreased vision and metamorphopsia. Of the 12, 7 eyes had type 3 ERMs, and 5 had type 2 ERMs. The 1 eye with an ERM in the peeling group was asymptomatic and no surgery was indicated.
“The findings seem to support the value of ILM peeling in primary RRD to help prevent ERM development. The results from the current study further bolster this hypothesis given that fewer than 2% of patients who underwent ILM peeling developed an ERM versus close to 50% of patients in the nonpeeling group. SS-OCT is helpful to define and classify the different types of ERMs and establish the surgical indication for their removal,” the authors concluded.
