**6. ERM-management**

#### **6.1. Indication for surgery**

Most thin ERMs are visually asymptomatic and can be followed up for a long time with periodical visits and with amsler card testing by the patient himself. In reported series regarding the natural evolution of an idiopathic ERM, it is reported that in a mean follow-up of 21 months, there was no significant change in mean VA of CRT or central volume of the macula [29]. The author's experience is also similar, especially for the initial severity, thin membranes without major tractional components. In asymptomatic cases, the OCT may reveal thickened macula with loss of central depression, and a CRT of higher than 330 microns with a VA of 20/20. So, only thickened macula due to ERM, which is measured with OCT imaging, does not correlate with the complaints of the patients. The retinal distortions induced by ERM contraction are believed to be the primary reason for visual impairment in idiopathic ERM, which can easily be observed with OCT imaging.

When indicated, the management of idiopathic ERMs is surgical. There are still no strict recommendations regarding the exact timing of the surgery. However, the most important indication is deciding the presence of visual complaints of the patients are related with ERMs, but not cataractous or refractive changes. As the mean age of patients with ERM is usually around their 70s, their lenses have frequently cataractous changes, which should be considered as a cause of blurred vision. On the other hand, the complaint of metamorhopsia is often more intolerable for the patient and is an indication for surgical removal of an ERM even though the visual acuity is high. If the tractional distortions in the retinal layers are not prominent, and the patient has cataract without any metamorphopsia, the patient can be offered a lens surgery first, and the ERM can be followed-up, informing the patient has a higher risk of having postoperative macular edema. On the other hand, if the surgical removal is indicated, a combined surgery of a pars plana vitrectomy and a lens surgery is usually preferred as cataractous changes usually increase fastly following PPV, necessitating a lens surgery soon after.

#### **6.2. Surgery**

studies performed have already shown the safety and feasibility of iOCT imaging [24, 25]. The most common posterior segment procedure was vitrectomy with membrane peeling, in 43% of which iOCT informed surgeon decision-making [24]. The following study, performed to evaluate a microscope-integrated iOCT system with a heads-up display, showed that iOCT data conflicted with the surgeon's impression of membrane peel completeness in 19% of cases [25]. The surgeons reported that use of iOCT provided valuable feedback in 71% posteriorsegment surgeries [26]. The author's experience is also compatible with the findings of the studies that, iOCT can show residual membranes if any, unconnected areas between ERM and the retina, and confirm if ERM/ILM peel is completed during ERM surgery. Although iOCT is a nice instrument to supplement surgical assessment, it is not available in most ORs, is costly,

Optical coherence tomography angiography (OCTA) is a new technology for imaging the microvasculature of the retina and choroid, using laser light reflectance of the surface of moving red blood cells to demonstrate vessels noninvasively. The vessels through different segmented areas of the eye can be imaged, and differences can be analyzed between scans. The image is segmented into four zones, namely, the superficial retinal plexus, the deep retinal plexus, the outer retina and the choriocapillaris. OCTA can show the changes in the retinal vasculature caused by macular traction of an ERM. OCTA can help to evaluate the depth and extent of foveal capillary distortion. Reduction in VA is found to be associated with this distortion [27]. Differences in foveal avascular area and decrease in parafoveal vascular density both in superficial and deep capillary plexus are also reported in the eyes following ERM surgery, and these changes were associated with worse postoperative VAs [28]. As more studies will be performed with OCTA imaging, more prognostic findings may be available for surgeons to

help decision-making for removal of ERM as well as to determine visual prognosis.

leakage, traction on the vessels, ischemia, or secondary neovascularizations.

Fundus fluorescein angiography (FFA) is usually not necessary in routine evaluation of ERMs, but it is helpful in secondary ERMs following retinal vascular occlusions or inflammations to assess not only the macular area but also the peripheral retinal circulation. It can demonstrate

Most thin ERMs are visually asymptomatic and can be followed up for a long time with periodical visits and with amsler card testing by the patient himself. In reported series regarding the natural evolution of an idiopathic ERM, it is reported that in a mean follow-up of 21 months, there was no significant change in mean VA of CRT or central volume of the macula [29]. The author's experience is also similar, especially for the initial severity, thin membranes without

and is apt to further advancements of the system in the future.

**5.2. Optical coherence tomography angiography**

74 OCT - Applications in Ophthalmology

**5.3. Fundus fluorescein angiography**

**6. ERM-management**

**6.1. Indication for surgery**

Epiretinal membrane surgery involves a pars plana vitrectomy procedure with ERM peeling. Internal limiting membrane peeling (ILM) is usually performed to prevent secondary membrane formation. It is already reported that ILM peeling decreased secondary membrane formations significantly [30]. A meta-analysis reported that vitrectomy with ILM peeling resulted in better visual improvement in long-term follow-ups and lower ERM recurrence rates [31]. On the other hand, other meta analyses reports found that although additional ILM peeling could result in a significantly lower ERM recurrence rates, it does not significantly influence postoperative best-corrected VA and central macular thickness [32, 33]. The postoperative VA is not found to be different in two groups with or without ILM peeling in idiopathic ERMS in a prospective trial [34]. The author's experience is also similar. In a prospective interventional case series, the efficacy and safety of combined peeling of ERM and ILM membranes with the single injection of mixture of tryphan blue and brilliant blue G dyes in eyes with idiopathic ERM was evaluated (Video). Seven (three pseudophakic and four phakic) eyes underwent vitrectomy and eight eyes had combined phacoemulsification and vitrectomy. Four phakic patients needed lens surgery with a mean of 10 months postoperatively. At postoperative month 6, the mean CMT decreased significantly from 502 ± 35 to 277 ± 43 μ. The mean VA significantly increased from 20/64 to 20/32 in all eyes with no recurrent ERM observed (**Figure 8**) [35].

ILM peeling maneuver should be performed cautiously to avoid secondary complications as a retinal hole formation, traumatic defects in the macular area, as well as phototoxicity. The surgery itself has the possible complications of a PPV, such as retinal tear and detachment, endophthalmitis, loss of ganglion cells, and others, which must be discussed with the patient.

meta-analysis of three studies reporting surgical results following small incision pars plana vitrectomy, in which the recurrence of ERM was around 1% [37]. Those with worse VA preoperatively gain more lines postoperatively. However, the eyes with higher preoperative VA tend to have a higher postoperative VA [38–40]. Poor preoperative VA, and long duration of symptoms are poor prognostic factors [36, 38–39]. Visual acuity improves in 1–6 months postoperatively. However, VA improvement can continue to increase following 1–2 years of surgery. Successful surgical intervention is associated with both decreased central foveal thickness (CFT) and improved VA [30–42]. However, central macular thickness is not necessarily correlated with postoperative VA [4–43]. Although CFT may be useful for evaluating the impact of ERM on baseline VA, it is probably not useful for predicting postoperative VA [6]. The preoperative OCT characteristics are more important. Intact preoperative inner segment ellipsoid (ISe) band is associated with a better postoperative VA than a disrupted preoperative ISe band in both idiopathic and secondary ERMs [38, 41–49]. The longer photoreceptor outer segment (PROS) length is also reported to be a good prognostic factor for the postoperative VA [39, 42]. It has also been shown that the integrity of outer photoreceptor cell layer as well as of ELM is related with better postoperative VA [50]. Postoperative increase in contrast sensitivity is associated with the thickness of outer retinal layer [44]. The preoperative degree of metamorphopsia was also found to be a prognostic factor for the postoperative degree of metamorphopsia, suggesting that surgery

Clinical Use of OCT in the Management of Epiretinal Membranes

http://dx.doi.org/10.5772/intechopen.79770

77

for ERM should be performed before development of severe metamorphopsia [39].

School of Medicine, Acıbadem Mehmet Ali Aydınlar University, Maslak Hospital,

In conclusion, OCT provides a very detailed information of all the retinal layers, and the vitreomacular interface. Epiretinal membranes are a frequent clinical finding in an aging eye, and sometimes result in decreased vision, and/or metamorphopsia. OCT, as a noninvasive, fast imaging system of the macula being more sensitive than the clinical examination has become the routine evaluation of ERMs. OCT imaging is used to diagnose, differentiate, manage, and follow ERMs. It also gives valuable information regarding the visual prognosis of the operated eye. Intact and continuous preoperative inner segment ellipsoid band, the longer photoreceptor outer segment, and the integrity of ELM are reported to be good prognostic signs. On the other hand, preoperative three-dimensional OCT evaluation of an ERM can also help the surgeons to identify any free edges of the ERM that may help in starting membrane peeling with reduced trauma. Lastly, OCT has recently been integrated into our operating rooms as intraoperative OCT and may support our decision-making during vitrectomy.

**7. Conclusion**

**Author details**

Sarıyer, Istanbul, Turkey

Address all correspondence to: nuracarr@gmail.com

Nur Acar

**Figure 8.** (a) SD-OCT image of a 73-year-old female presented with visual blurring and metamorphopsia with a VA of 0.6 shows a tightly adherent hyperreflective layer of ERM on the macula. The central retinal thickness is increased with traction on the fovea causing intraretinal cystic changes seen as hyporeflective spaces in the inner retina. The outer retinal layers are intact. The symptomatic patient underwent vitrectomy with ERM and ILM peeling. (b) SD-OCT at postoperative month 1 shows normal retinal architecture with normal retinal thickness. There is small depression on the superior side. The patient's metamorphopsia decreased with a VA of 1.0. (c) SD-OCT image at postoperative year 5 is the same with no recurrent ERM observed during 5 years of follow-up.

#### **6.3. Surgical prognosis**

Following ERM removal increase in VA of two or more lines in 60–85% of cases 6–12 months postoperatively with around 50% gaining a VA of 20/50 or better [36]. The mean preoperative and postoperative VA has been reported to be 20/110 and 20/55 [37]. This data were a meta-analysis of three studies reporting surgical results following small incision pars plana vitrectomy, in which the recurrence of ERM was around 1% [37]. Those with worse VA preoperatively gain more lines postoperatively. However, the eyes with higher preoperative VA tend to have a higher postoperative VA [38–40]. Poor preoperative VA, and long duration of symptoms are poor prognostic factors [36, 38–39]. Visual acuity improves in 1–6 months postoperatively. However, VA improvement can continue to increase following 1–2 years of surgery. Successful surgical intervention is associated with both decreased central foveal thickness (CFT) and improved VA [30–42]. However, central macular thickness is not necessarily correlated with postoperative VA [4–43]. Although CFT may be useful for evaluating the impact of ERM on baseline VA, it is probably not useful for predicting postoperative VA [6]. The preoperative OCT characteristics are more important. Intact preoperative inner segment ellipsoid (ISe) band is associated with a better postoperative VA than a disrupted preoperative ISe band in both idiopathic and secondary ERMs [38, 41–49]. The longer photoreceptor outer segment (PROS) length is also reported to be a good prognostic factor for the postoperative VA [39, 42]. It has also been shown that the integrity of outer photoreceptor cell layer as well as of ELM is related with better postoperative VA [50]. Postoperative increase in contrast sensitivity is associated with the thickness of outer retinal layer [44]. The preoperative degree of metamorphopsia was also found to be a prognostic factor for the postoperative degree of metamorphopsia, suggesting that surgery for ERM should be performed before development of severe metamorphopsia [39].

## **7. Conclusion**

In conclusion, OCT provides a very detailed information of all the retinal layers, and the vitreomacular interface. Epiretinal membranes are a frequent clinical finding in an aging eye, and sometimes result in decreased vision, and/or metamorphopsia. OCT, as a noninvasive, fast imaging system of the macula being more sensitive than the clinical examination has become the routine evaluation of ERMs. OCT imaging is used to diagnose, differentiate, manage, and follow ERMs. It also gives valuable information regarding the visual prognosis of the operated eye. Intact and continuous preoperative inner segment ellipsoid band, the longer photoreceptor outer segment, and the integrity of ELM are reported to be good prognostic signs. On the other hand, preoperative three-dimensional OCT evaluation of an ERM can also help the surgeons to identify any free edges of the ERM that may help in starting membrane peeling with reduced trauma. Lastly, OCT has recently been integrated into our operating rooms as intraoperative OCT and may support our decision-making during vitrectomy.
