**6. Results and prognosis**

#### **6.1. Functional results**

In general, visual acuity seems to improve following ERM surgery. More than 50% of patients gain 2 or more logMAR lines and less than 10% end up with lower postoperative VA [74-76]. Preoperative vision is usually 20/63 or worse, but cases with good visual acuity have been reported to benefit from surgery, too [77]. Improvement in vision usually occurs in the first two to three months, but complete recovery may require six to 12 months following surgery. Additionally, cataract extraction is very likely to be needed shortly after ERM peeling, as nuclear sclerosis accelerates after vitrectomy [75, 77-79].

Overall, visual prognosis depends on preoperative vision, the duration of symptoms and the preoperative anatomical status of the fovea and retinal layers [74, 80]. Postoperative BCVA is better in patients with good preoperative VA, but the gain in letters seem to be greater for patients with poorer preoperative VA. This means that patients with low preoperative visual acuity do not enjoy complete recovery after macular membrane removal. Limited restoration of the VA in these patients can be due to chronic traction, which results in permanent retinal vascular incompetence. Subsequent retinal vascular leakage and persistent cystoid macular oedema restrict the restoration of macular function and anatomy.

Metamorphopsia, one of the main reasons for patients deciding to undergo surgery, has not been investigated in a methodical and quantified manner. In the few studies that have studied metamorphopsia, it appears to improve after surgery and can happen as early as the first postoperative month [81-82]. Its preoperative existence affects postoperative visual outcomes, but the duration of preoperative symptoms do not affect the postoperative visual acuity three months after surgery [81].

#### **6.2. Anatomical outcome**

arcades. The simultaneous removal of the ILM is imperative for some surgeons, but it is not

Following ERM removal, inspection of the peripheral retina follows; if this shows no iatrogenic damage, surgery is completed by trocar removal and sclerotomy closure. If iatrogenic damage is present, breaks in the periphery without subretinal fluid accumulation can be treated by laser retinopexy or cryoretinopexy. The presence of significant amounts of subretinal fluid

Although scleral ports in small gauge vitrectomy are designed so that no sutures are necessary, careful inspection of the water tightness of the ports at the conclusion of surgery is mandatory in order to avoid early postoperative hypotony. Gentle massage of the site of scleral incision after trocar removal can improve a relatively leaky incision. Occasionally, the insertion of a

In general, visual acuity seems to improve following ERM surgery. More than 50% of patients gain 2 or more logMAR lines and less than 10% end up with lower postoperative VA [74-76]. Preoperative vision is usually 20/63 or worse, but cases with good visual acuity have been reported to benefit from surgery, too [77]. Improvement in vision usually occurs in the first two to three months, but complete recovery may require six to 12 months following surgery. Additionally, cataract extraction is very likely to be needed shortly after ERM peeling, as

Overall, visual prognosis depends on preoperative vision, the duration of symptoms and the preoperative anatomical status of the fovea and retinal layers [74, 80]. Postoperative BCVA is better in patients with good preoperative VA, but the gain in letters seem to be greater for patients with poorer preoperative VA. This means that patients with low preoperative visual acuity do not enjoy complete recovery after macular membrane removal. Limited restoration of the VA in these patients can be due to chronic traction, which results in permanent retinal vascular incompetence. Subsequent retinal vascular leakage and persistent cystoid macular

Metamorphopsia, one of the main reasons for patients deciding to undergo surgery, has not been investigated in a methodical and quantified manner. In the few studies that have studied metamorphopsia, it appears to improve after surgery and can happen as early as the first postoperative month [81-82]. Its preoperative existence affects postoperative visual outcomes, but the duration of preoperative symptoms do not affect the postoperative visual acuity three

yet clear whether it affects recurrence rates [69-70] or retinal function [71-73].

necessitates internal drainage, retinopexy and gas tamponade.

small suture may be necessary for a leaky scleral incision.

nuclear sclerosis accelerates after vitrectomy [75, 77-79].

oedema restrict the restoration of macular function and anatomy.

**5.3. Conclusion of surgery**

124 Advances in Eye Surgery

**6. Results and prognosis**

**6.1. Functional results**

months after surgery [81].

Postoperative reduction of the central macular thickness (CMT) has been a consistent finding in most studies [75, 83]. Figure 2 shows the anatomic restoration of the fovea (b) and following the removal of the epimacular membrane (a) in one of our cases, six months postoperatively. Visual recovery, however, is not always correlated with the decrease of retinal thickness. Recent studies have correlated other preoperative and postoperative anatomical features with visual outcomes. OCT represents an invaluable tool for the assessment of these features, primarily by using high definition techniques. Ellipsoid zone (IS/OS) integrity, photoreceptor outer segment (PROS) length and external limiting membrane (ELM) integrity represent some of the anatomical characteristics that appear to play an important role in functional prognosis. Significant changes in ellipsoid integrity (IS/OS) have been correlated with visual outcomes, while postoperative elongation of the PROS have been described in successful cases [84].

**Figure 2.** Anatomical restoration after ERM peeling; a) preoperative image of contracted ERM with retinal thickening and cystoid macular oedema; b) six months after surgery the foveal anatomy has greatly improved. Small intraretinal cysts can still be seen along with some changes in the outer retinal layers.

On the other hand, although postoperative visual field loss is known to occur in some cases following ERM surgery, its correlation with anatomical changes in the OCT has not been confirmed by the literature. The effect of surgery on the nerve fibre layer (NFL) and the ganglion cell layer (GCL) are under intense investigation, especially with "*en face*" OCT and other sophisticated techniques. However, the results on whether there is loss of neuronal or glial tissue remain ambiguous, as do reasons for the late deformation of the central retina, often observed following ERM surgery. Based on modern retinal imaging modalities, it is believed that retinal reconstruction continues for months after ERM peeling [85-86].

#### **6.3. Prognosis of different ERM subtypes**

Secondary epiretinal membranes have worse prognosis than idiopathic membranes [69]. Limited visual recovery, as well as higher recurrence rates, is reported. Diabetic membranes are difficult to manage, as they are accompanied by severe retinal damage that can lead to serious complications including haemorrhage, detachment and re-proliferation of the connec‐ tive tissue [87]. Postoperative ERMs (including ERMs developed after vitrectomy for retinal detachment, but also after laser or cryo-retinopexy) have limited visual recovery, especially when the macula is detached [88]. Finally, inflammatory membranes illustrate variable results, depending mostly on the effect of the subjacent inflammation on the retinal function [89].
