**10. Macular hole closure**

A macular hole is said to be closed when there is flattening and reattachment of the hole rim along the whole circumference of the macular hole (**Figures 5** and **6**).

Two types of closure have been defined [43].


Imai et al. [44] gave another OCT-based classification of macular hole closure and divided it into three types:


**Figure 6.** *Macular hole closure after successful vitrectomy, ILM peeling and gas tamponade.*

**Figure 7.** *Full-thickness macular hole with operculum.*

The various lines seen in the outer retinal on OCT scanning have been mentioned earlier in this chapter, namely the External limiting membrane (ELM), Inner segment/Outer segment junction (IS/OS junction) or Ellipsoid zone (EZ), Cone outer segment tips (COST) or Interdigitation zone (IZ) and Retinal pigment epithelium (RPE).

Structural changes in the macular region after surgery are correlated to photoreceptor alterations [45–48]. They can be related to the outer retinal bands seen on OCT

**Figure 8.** *Macular hole closure after surgical treatment.*

scanning. The ELM is the first retinal layer to recover, followed by the IS/OS, and lastly the COST (**Figure 8**).

Min Woo Lee et al. [49] analysed the process of recovery of the ELM, Outer nuclear layer (ONL), and EZ after surgical treatment. They tried to identify the factors affecting changes in visual acuity and those associated with EZ recovery. They divide full-thickness MH healing into the following stages: the first stage occurred when the traction from ILM to the neuroretina was released after surgery resulting in the resolution of intraretinal cysts, this phase occurred when the inner retinal layers grew to the centre of the macular hole and two edges were connected by forming a tissue bridge. At this stage, SRF could still be found on B-scan. Finally, the SRF resolves and photoreceptors begin remodelling, which could lead to restoration of the ellipsoid area (**Figure 9**).

#### **11. Role of the internal limiting membrane**

The ILM is the most superficial layer of the retina and is formed by the Muller cell footplates together with a fibrous component. This membrane is 400 nm thick at the retinal periphery, rising to about 1400 nm in the macular region [50]. This structure provides greater mechanical strength than retinal cell layers, being responsible for 50% of retinal stiffness. The rationale for its removal is to relieve all tangential traction around the macular hole and improve hole closure rates [51–53].

During macular hole surgery, central vitrectomy is usually followed by PVD induction by placing the cutter on aspiration mode in the proximity of the optic disk until a Weiss ring is noticed and a wave of circumferential vitreous separation is seen. Vitreous removal with a high-speed cutter to the retinal periphery is then performed. At this stage, any epiretinal membranes (ERM) surrounding the macular hole should be stained and removed up to the borders of the hole. If no ERM is identified, then

**Figure 9.** *Macular hole closure: Preoperative optical coherence tomography (OCT) and 10 months postoperative OCT.*

most surgeons would routinely remove the ILM. The advent of tissue stains and dedicated surgical instrumentations allows the identification and removal of the inner limiting membrane and this procedure can be described as total peeling (TP) when the ILM around the MH is removed or foveal sparing peeling (FSP).
