**7. Surgical treatment**

#### **7.1 Timing**

Jaycock et al. [16] reported a closure rate of 94% among patients having surgery within 1 year of the onset of symptoms. The anatomical success was noted to be reduced to 47% when surgery was postponed more than 12 months. Macular holes operated after 1 year yield poor functional improvement even if anatomic closure is obtained. Limited visual improvement may be obtained after successful closure of chronic MH and is linked with the MH duration [17]. One possible reason for a failed surgical outcome in chronic MH surgery may be due to a strong adhesion of the photoreceptor layer of the retina to the underlying RPE [18–20].

#### **7.2 Evaluation of outcome of surgery**

It is difficult to accurately compare the results of different studies due to the lack of a uniform method for determining the integrity of the outer retinal layers after MH vitrectomy. The rapid development of the OCT has facilitated images with a very high resolution. This has allowed accurate interpretation of the outer retinal layers and the ability to compare them to histological sections of the retina.

The outer retinal layers can be divided into 4 lines or bands [21] and the presence of well-defined bands is associated with good vision. The first band arises from the External Limiting membrane (ELM). The second band is referred to as the inner segment – outer segment (IS-OS) intersection of the photoreceptors. The third band has been described as the COST (cone outer segment tips), intermediate line and more recently the interdigitation zone (IZ). The fourth band corresponds to the RPE. Iwasaki et al. [22] also described a method in which the ELM recovery rate and the EZ recovery rate were evaluated in the treated groups.

Caprani et al. [23] describe the restoration of outer retinal layers from the external limiting membrane (ELM), inner segment/outer segment junction (IS-OS), and cone outer segment tips (COST) to retinal pigment epithelium (RPE) after IMH surgery and its relation to visual acuity. They classified the layers as either present or absent after MH surgery with ILM peeling. They also observed the ELM was the first layer to be restored in the healing process, while the integrity of the ellipsoid zone was present in 53.5% of patients at 3 months and in 73.91% at 6 months.

#### **7.3 Surgical technique**

Surgical treatment was pioneered in 1990 by Kelly and Wendel [24] by performing 20 gauge pars plana vitrectomy, PVD induction, intraocular gas tamponade and postoperative face-down positioning. They reported an anatomical closure rate of 58% and 73% and visual improvement in 42% and 55% of cases in two consecutive reports.

Eckardt [25] in 1997, introduced the concept of internal limiting membrane (ILM) peeling in the management of macular holes. Peeling of the internal limiting membrane relieves the tangential traction caused by glial cells and improves the anatomical and visual success rates of macular hole surgery.

A Cochrane review in 2013 [26] showed better visual results, anatomical closure rates and lower re-operation rates in patients who underwent ILM peeling when compared to those who underwent pars plana vitrectomy alone.

#### **7.4 Microincision vitreoretinal surgery (MIVS)**

The advent of smaller gauge and better instrumentation, tissue staining during ILM removal, combined phaco-vitrectomy surgery and reduced or no postoperative face-down positioning are all factors that have facilitated surgery and made it technically less challenging as well as being less obtrusive and difficult for the patient.

Shift to small gauge instrumentation in the last 20 years may have resulted in a slightly increased duration of the vitrectomy operation due to the increased cut rates and slight reduction of fluid passage in the eye. MIVS has however caused a significant reduction in complications like entry site retinal breaks and vitreous traction-related retinal damage (**Table 2**).


**Table 2.**

*Comparison of 20-G, 23-G, and 25-G vitreous cutters and instrumentation.*

#### **7.5 Gas tamponade**

Filling the vitreous cavity with gas encourages hole closure by preventing fluid from accessing the hole and may facilitate the formation of a glial plug that can contract and help with hole closure. The buoyancy effect of the gas is also thought to play a role by direct pressure on the hole and hence the reason that face-down posturing has been recommended in the postoperative period. Gas mixtures used in different percentages are C3F8, C2F6, SF6 and air. Recent studies have shown that longer-acting gases like C3F8 and C2F6 may not be needed as SF6 and air show similar anatomic results in terms of hole closure and better patient compliance [27, 28]. Silicone oil is rarely used as a tamponade agent and needs a further surgical procedure to remove the oil.

#### **7.6 Postoperative prone posturing**

Facedown posturing (FDP) has been recommended because the gas bubble with its surface tension forces may support the apposition of the MH edges and also provide a scaffold for the migration of glial cells and blocking fluid entry into the hole.

The force of the gas bubble is greatest at the apex of the arc of contact to the retinal surface and diminishes from this point [29].

Postoperative face-down positioning night and day for a week was recommended as a critical step for many years to increase the buoyancy force exerted on the posterior pole but studies have subsequently shown that prolonged face-down posturing may not be needed especially for smaller holes. Recent publications report closure rates for small- to medium-size MHs at around 95% in both postured and nonpostured groups indicating that prolonged posturing is not necessary for MH closure after surgery. The authors concluded that face-down posturing is not necessary for medium-sized MHs [30–32]. Large holes >400 microns may benefit from prolonged postoperative posturing, but studies still show inconclusive results [33].

Ye et al. [34] in a meta-analysis of five randomised controlled trials compared MH surgeries with ILM peeling with postoperative FDP versus those with non-supine posturing (NSP). The MH closure rate was higher in the FDP group, with a significant difference in the closure rate for MH with size >400 μm, but not for those <400 μm.

Eckardt et al. [35] considered stopping the FDP as soon as the OCT confirmed the closure but in case of non-closure on day 3, it required a second procedure on day 5 or 6 to facilitate hole closure. It has been noted that increased duration between the first and second surgery when there is failed primary repair may result in a worse visual and anatomical outcome [36–38].

Nearly all patients having vitrectomy surgery with a gas bubble will develop cataract. A pilot study by P R Simcock and S Scalia [39] showed that combining lens removal at the time of vitrectomy resulted in greater space for the gas bubble and better tamponade and patients had successful hole closure without having to adopt a prone posture as well as the advantage of not having to return for further cataract surgery.

Chakrabarti et al. [40] described the use of autologous gluconated blood (AGBL) in the macular area for treating MH without the use of intraocular gas or prone positioning. They report no significant side effects and 26 patients with large MH's, obtained 100% closure using an inverted ILM flap and AGBL to encourage macular healing with good functional outcome. The technique involves a preparation of AGBC before the surgery (1 mL of 5% glucose added to 2 mL of autologous blood) then an ILM flap was created and AGBC on top to create a macular plug. This technique allowed the patients to adopt a comfortable position without gas tamponade.

#### **8. Staining**

Vital dyes were introduced more than 20 years ago to allow better visualisation and removal of the vitreous and staining and removal of epiretinal membranes and the internal limiting membrane [41, 42].

#### **8.1 Triamcinolone acetonide**

Triamcinolone crystalline microparticles are trapped in the vitreous gel facilitating gel removal by improving visualisation and determining if there has been a vitreous separation from the retina. The microparticles also tend to settle on membrane surfaces creating a demarcation between the peeled and remaining membrane.

#### **8.2 Indocyanine green (ICG) and Infracyanine green (IfCG)**

ICG green stains the ILM because of its affinity to laminin and collagen type IV within the ILM. ILM peeling was popularised as a result of this stain as it was a technically challenging procedure to perform without the stain. It has however been criticised due to complications associated with cytotoxic and phototoxic effects on the exposed RPE. Infracyanine Green at a concentration of 0.5 mg/ml also allows good visualisation of the ILM but with a better safety profile.

#### **8.3 Trypan blue**

Trypan blue 0.2% is also used to stain the ILM or ERM during vitreoretinal surgery and is often injected after a fluid air exchange to increase the staining of the membrane (**Figure 4**).

**Figure 4.** *Trypan blue is injected under the air bubble.*
