Introduction

The history of the macular buckling (MB) technique began in 1957 [1] when, for the first time, Schepens, Okamura, and Brockhurst used a polyethylene tube radially placed to buckle the macular area in highly myopic patients with retinal detachment secondary to a macular hole (MHRD). Later on, several methods were proposed for treating MHRD using an episcleral approach [2,3,4,5,6,7,8,9,10,11,12,13], but despite satisfying anatomical reattachment rates, the episcleral approach was not free from severe complications. Until the 1980s, the aim of surgical treatment for MHRD was limited to anatomical reattachment; functional results were a secondary consideration. In addition to the difficulties related to the surgical procedure, this may be the main reason why the technique was almost completely abandoned for about 20 years.

That was the situation until the 2000s, when Sasoh et al. [14] published their study on 33 highly myopic eyes treated with MB, achieving a retinal reattachment rate greater than 90% and sheding a bright new light on the problem. Now, since 2011, we have witnessed an extraordinary boom, with several studies on MB published every year and increasing use of this procedure worldwide for three main surgical indications: (1) MHRD, (2) myopic foveoschisis (MFS) with or without foveal detachment, and (3) macular hole (MH) with concomitant MFS. To date, the reported anatomical success rates of MB in highly myopic eyes have shown differences between studies and particularly, marked differences in comparison with the transvitreal approach. Thus, the aim of this report is to review the published articles on this subject in order to define the current state of the art of this relatively new surgical technique and to compare both anatomical and functional results with those obtained by pars plana vitrectomy (PPV).

Methods

A search was carried out in the PubMed database of articles published from 2000 to 2016, using the heading high myopia, and inserting the keywords macular buckle, episcleral surgery, macular hole, retinal detachment due to macular hole, and myopic foveoschisis combined in different ways. Only articles in the English language were considered, and all type of studies (retrospective, prospective, comparative, randomized, and case series) were included. Case reports in which the abstract or full text (if any) was unavailable are mentioned, but were excluded from the analysis.

The studies were divided into different groups according to the underlying condition for which the procedure was used. The number of eyes, degree of myopia (spherical equivalent [SE] and/or axial length [AL]), duration of follow-up, type of buckle, use or not of concurrent pars plana vitrectomy (PPV), MH closure and retinal reattachment rates, resolution of foveoschisis, and changes in best corrected visual acuity (BCVA) reported in the studies were recorded and assessed. The use of postoperative optical coherence tomography (OCT) to determine the MH status, as well as the intraoperative and postoperative complications, including retinal redetachment rates secondary to persistent MH, were also evaluated. When MB was used in different types of myopic traction maculopathies within the same study, the outcomes were analyzed separately for each condition and the results summarized in the appropriate table. When reported, the results in a comparative PPV group within the same study are not included in the tables, but are discussed along the review. As well, both anatomical and visual outcomes after MB have been also compared with those obtained by PPV alone depending on the original pathology. Such comparison will be discussed in details and will be limited to the “Discussion” section.

Results

Thirty-one published articles on surgical outcomes after MB in highly myopic patients were retrieved from PubMed and analyzed. The studies were divided into three groups depending on the type of myopic traction maculopathy treated. Sixteen studies included patients affected by MHRD (MHRD group), 11 included patients with MFS with or without foveal detachment (MFS group), and 4 reported on patients with MH and MFS (MH-MFS group). Pre- and postoperative data are described in Tables 1, 2, and 3, respectively. Anatomical and functional results in these three different groups are shown in Table 4, while intra- and postoperative complications after MB are summarized in Table 5. One of the case series found included highly myopic patients treated with MB for MH without foveoschisis or retinal detachment; it is cited separately at the end of this section. Technical features of the most commonly used posterior buckles are described in Fig. 1. Independently of the material used for creating a macular plomb, an additional stainless steel or titanium wire was also used in some cases, allowing the MB to be bent as needed until the desired shape (T-shape or L-shape) was obtained for correct indentation. In addition, a 29G chandelier light was inserted into the indenting head of the MB for optimal positioning when needed [14,15,16,17].

Table 1 Published studies on MHRD treated with MB technique (MHRD group, 272 eyes)
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Table 2 Published studies on MFS with or without foveal detachment (FD) treated with MB technique (MFS group, 178 eyes)
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Table 3 Published studies on MH with foveoschisis treated with MB technique (MH-MFS group, 39 eyes)
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Table 4 Anatomical and functional results after MB
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Table 5 Intra- and postoperative complications considering all 31 published studies on MB (total, 489 eyes)
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Fig. 1
figure 1

Technical features of the most commonly used posterior buckles

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MHRD group

Data from the 16 studies on patients treated with MB for MHRD (272 eyes) are summarized in Table 1. Primary retinal reattachment ranged from 81.8% [18] to 100%, and MH closure rates from 40% [19] to 93.3%. However, it is not clear whether OCT scans were performed to assess the MH status postoperatively in most of these series, and further reoperations were needed to achieve a final anatomical success rate of 100% [14, 20,21,22,23]. Eight of the 272 eyes (2.9%) underwent a second surgical approach because of persistent posterior detachment after MB. Additional hexafluoride sulfur (SF6) injection [14] or PPV with silicone oil tamponade [20] was used in two eyes and one eye, respectively, and the MB was replaced in five eyes [21, 22]. In one case, the MH was primarily closed and the macula attached, but a second surgery was performed because of persistent peripheral retinal detachment [23].

In five studies reported since 2013 [16, 23,24,25,26], concurrent PPV was performed during primary MB surgery in most patients. In another study, 21 eyes were treated with MB because of recurrent MHRD after primary vitreous surgery [23]. Overall, some patients had undergone unsuccessful PPV (from 1 to 3 in some cases) in 8 studies (75/272 eyes, 27.5%) [17,18,19, 23, 24, 26,27,28]. Among them, MB alone was preferred as the second surgical approach in four studies, and was performed in silicone oil-filled eyes in some cases [18, 19, 27, 28]. Despite episcleral surgery, an infusion cannula was positioned in all patients in one of these studies to better control intraocular pressure while placing the buckle [27]. In the series of Ripandelli et al. [20] and Bedda et al. [29], posterior transcleral drainage was also used in all patients, and in Ripandelli’s study [20], an additional 360° encircling band was placed. In the study of Qi et al. [30], all patients underwent PPV without internal limiting membrane (ILM) peeling 1 week after MB surgery.

Axial length was not measured in most patients, but when this parameter was reported, the mean value was often greater than 30 mm. In addition, the mean SE was always greater than − 9.00 D. The mean duration of follow-up exceeded 1 year in 13/15 studies, with a maximum of 15 years in the study by Theodossiadis et al. [21].

The macular exoplant was made of solid silicone in nine studies and silicone sponge in five others. In the remaining two studies, donor sclera [30] and suprachoroidal injection of long-acting hyaluronic acid [25] were used, respectively.

Concerning the functional outcome, BCVA improvement rate ranged from 27.3 to 100%. The rate was below 50% in 2 studies and was higher than this value in 14, reaching 100% in 6 case series. In the study in which visual acuity increased in only 27.3% of cases [18], the MH closure rate was not reported and all patients (n = 11) had undergone previous vitreous surgery.

Intra- and postoperative complications are reported in Tables 1 and 5. In two case series, there were no complications of any type, whereas in three studies, complications were not reported. Overall, the most common complication was scleral perforation (7/272 eyes, 2.6%), followed by prolapse of the orbital fat in 1 study [28] (6/272 eyes, 2.2%), and MB malpositioning (5/272 eyes, 1.8%). Temporary muscle disinsertion while placing the buckle was required in five studies [15,18,19,20, 28].

MFS group

Data on MB in patients with MFS (11 published articles) are summarized in Table 2. In total, 178 eyes underwent the MB technique. In all except one study [31], the presence or not of foveal detachment was also documented (presence, 29.2%; absence, 48.8%). Resolution of foveoschisis reached 100% in 5 of the 11 studies [16, 25, 30, 32,33,34], and ranged from 25% [35] to 94.9% [31] in the others. The final foveal reattachment rate was 100% in eight case series, 66.6% in the study of Devin et al. [18], 94.9% in the series of Li et al. [31], and was unreported in one study.

Concurrent PPV with [16] or without [25, 33] ILM peeling was performed in three studies, and air or gas tamponade was used in most cases. However, in the studies of Li et al. [31] and Qi et al. [30], all patients underwent PPV without ILM peeling at 1 month and 1 week after MB surgery, respectively, in a two-step approach. Some patients had undergone previous PPV in only two case series [18, 25]. Overall, there was no need for reoperations after MB, except in the two-step studies of Li [31] and Qi. [30] However, in the series of Parolini et al. [16], 3 of 14 patients treated with MB alone received additional PPV with ILM peeling for residual tangential traction.

The mean AL and SE values, when available, were 29.65 mm and −17.3 D, respectively. Mean follow-up ranged from 8 months to more than 6 years. Regarding the type of buckle, a solid silicone exoplant was used in three studies, whereas indentation was achieved using donor sclera in five. In the remaining three case series, silicone sponges with stainless steel wires [16], suprachoroidal injections of long-acting hyaluronic acid [25], and three-armed adjustable silicone capsules [36] were preferred. Overall, the final BCVA improved in 33.3 to 90% of cases.

As is shown in Table 5, the most common complications were MB removal (7/178 eyes, 3.9%), retinal pigment epithelium (RPE) changes, and choroidal effusion (6/178 eyes each, 3.3%). Recurrent MFS was reported in only one study [37] (3/178 eyes, 1.6%). Among the total of 178 eyes, postoperative MH developed in 1 eye and MHRD in another, in 2 different studies [30, 37]. MH occurred in a patient treated with MB alone, and MHRD occurred in a vitrectomized eye. Muscle disinsertion was required in one study [18], but muscle limitations, including esotropia and abduction deficiency were reported in three different series [33, 36, 38].

MH-MFS group

Data concerning the four published studies in patients with MH-MFS are summarized in Table 3. Thirty-nine eyes were treated with this technique. Mean AL was 31.03 mm and mean SE, when reported, was greater than − 15.0 D. In two of the four studies, mean follow-up exceeded 1 year. A solid silicone MB was used in three series and donor sclera in Qi’s study [30]. MB was combined with PPV in two studies [26, 39] and in one case series all patients underwent PPV without ILM peeling 1 week after MB surgery [30]. Overall, MFS resolution and MH closure were achieved in 100% of cases.

In the series of Burès-Jelstrup et al. [39], 16 patients underwent MB in addition to PPV, ILM peeling, and intraocular gas tamponade. Three patients had undergone previous vitreous surgery and one still had silicone oil within the vitreous cavity. OCT scans showed that the MH had closed and foveoschisis had resolved in all cases. Postoperative visual acuity improved in 81.25% of patients. In one eye, the exoplant was removed due to extrusion 7 months after surgery. However, the MH remained closed and MFS did not recur. Among the three eyes treated with MB and PPV in Qi’s two-step approach [30], MFS resolved and the MH closed in all cases, with subsequent functional improvement. In the series of Cacciamani et al. [40], mean axial length was greater than the values reported in the other studies, and all 15 patients were successfully treated with MB alone. Nonetheless, BCVA improved in 86.7% of cases, and postoperative macular RPE changes were reported in six eyes. Lastly, five eyes were successfully treated in the case series reported by Mura et al. [26]. Three patients who had previous vitreous surgery with silicone oil tamponade received MB alone, while MB was combined with PPV and ILM peeling in the other two patients. In all patients except one, silicone oil was the preferred intraocular tamponade. Final BCVA increased in four patients, and no complications were reported.

Overall, the most common complication was RPE disturbance in 15.4% (6/39) of eyes (Table 5).

Additional data from comparative studies on MB vs PPV

In the total of 31 published studies, only 3 case series included a control group of patients treated with PPV. In the comparative study of Ripandelli et al. [20] on MHRD cases, the retina was reattached after primary PPV in 11 of 15 eyes (73.3%), but MH closure was achieved in only 4 of these 11 eyes (36.3%). Moreover, 4 of 15 patients who underwent PPV alone had retinal redetachment because of a persistent MH; all were successfully treated with additional macular buckling. In the series of Ando et al. [22], 14 of 28 eyes (50%) with MHRD were successfully treated with primary PPV (data concerning postoperative MH status were not available). However, ten patients were retreated with additional MB as secondary surgery, achieving a final retinal reattachment rate of 85.7% (24/28 eyes). In Qi’s last series [30], which included patients with MHRD, MFS, and MH-MFS, postoperative MHRD developed in 3 of 14 eyes (21%) in the control group treated only by PPV. MB was then applied in all three eyes; the retina was reattached, but the MH remained open in all cases.

Supplemental data: MB in myopic MH without foveoschisis or retinal detachment

As was mentioned above, five patients (mean axial length, 30.8 mm) with MH without foveoschisis or retinal detachment in the series of Mura et al. [26] were also treated with the MB technique using a solid silicone exoplant. Two received MB alone because of previous vitreous surgery with silicone oil tamponade, while the other three patients were treated with combined MB and PPV, with ILM peeling and gas injection. MH closure and improved BCVA were obtained in three of the five patients (60%), and there were no intraoperative or postoperative complications.

Discussion

Various surgical procedures have been proposed for the treatment of high myopia and posterior staphyloma-related conditions [41] such as MHRD [5], MFS with or without foveal detachment [42], and MFS associated with MH [43,44,45,46,47,48,49,50,51]. For many years, PPV with intravitreal gas or silicone oil injection with or without ILM peeling was preferred as the first approach to treat MHRD [52, 53] and MFS [32]. However, posterior silicone exoplants have been used since the 1950s [1], but it is only in the last 15 years that this “old classic” surgical technique has started to regain ground among vitreoretinal surgeons to treat high myopia patients. Until 2011, the common belief was that the MB technique was surgically challenging and required a longer learning curve than PPV. The technical difficulties and risk of injury to the surrounding ocular structures seemed to restrict this procedure from becoming widespread. But as time went on, MB has been gradually recognized as the only way to mechanically counteract the pulling effects of the posterior staphyloma, relaxing the retina, thus facilitating MH closure and retinal reattachment.

To determine the current role of MB in high myopic patients, we reviewed several previous studies focused on the anatomical and functional outcomes of this technique. However, as hundreds of studies have been published on PPV in highly myopic eyes, a detailed comparison between PPV and MB seems essential to provide the basis for tailored surgical treatment, specific to this population. For this reason, some important results obtained after vitreous surgery will be also discussed in the following sections, organized according to the original retinal condition.

MHRD group

When planning the best surgical approach to treat MHRD in highly myopic eyes, the two main issues usually considered are achieving MH closure and retinal reattachment. When these two goals are not attained, visual improvement is rare. However, certain additional questions should be examined: (1) Is the primary closure of the MH so important? (2) Is anatomical success influenced by axial length? and (3) What is the most effective intraocular tamponade in case of PPV with or without MB?

Postoperative anatomical outcomes and the importance of MH closure

As reported in Table 4, when MB is performed, primary retinal reattachment and MH closure rates range from 81.8% [18] to 100% and from 40% [19] to 93.3%, respectively. In the total of 16 studies reviewed, only 2.9% of patients required a second surgery because of persistent posterior detachment due to an unclosed MH after MB. Interestingly, in 8 studies [17–19, 23, 24, 26–28] including 75 of 272 eyes (27.5%), previous unsuccessful PPV (1–3 procedures) had been carried out before the episcleral approach, thus confirming that MH closure seems mandatory to avoid retinal redetachment in highly myopic eyes undergoing PPV. In our previous comparative study, 21 eyes were retreated with additional PPV and MB because of recurrent MHRD after vitreous surgery [23]. Although the reattachment rate was 90.5%, the MH closure rate of 57% was lower than in the previously untreated patients. Nonetheless, no retinal redetachment has been reported in patients with persistent MH who have undergone MB, suggesting that combined MB and PPV could be used as the first-line treatment in these patients and, secondly, that persistent MH rarely progresses to retinal redetachment when supported by MB. Because of the relative lack of elasticity of the retina and the change of macular surface shape from extremely concave to flat or even convex, MB may contribute to relieving the anteroposterior traction induced by the staphyloma and the stretched retinal arteries, thus facilitating MH closure.

When compared with vitreous surgery as reported in three comparative studies [20, 22, 30], the anatomical success rates, including both retinal reattachment and MH closure, are lower than those obtained with MB. In the study of Ripandelli et al. [20], primary retinal reattachment and MH closure rates after PPV were 73.3 and 36.3%, respectively, compared to 93.3% of both rates obtained with MB as the first line treatment. Ando et al. [22] showed similar results, achieving retinal reattachment in 50 or 93.3% of cases after PPV or MB, respectively. Finally, also in the study of Qi et al. [30], the anatomical success was greater in case of MB than PPV (100 vs 79%).

All this means that in these three case series, 21 to 50% of patients, respectively, who underwent PPV for MHRD had retinal redetachment because of a persistent MH. Interestingly, in all these cases, the retina was successfully reattached with additional MB.

As further evidence, in the study by Chen et al. [54], 57 eyes with MHRD were treated by 6 different surgical approaches including MB and/or PPV with gas or silicone oil tamponade, achieving a general primary reattachment rate of 43.9%. Considering this result, the authors concluded that the main problem was the inability to obtain primary MH closure with PPV, and that even when the MH was closed, it often reopened after PPV.

In the absence of randomized clinical trials investigating whether to combine episcleral and vitreous surgery in MHRD and determining the best choice for first-line treatment, these decisions seem to remain strongly related to the surgeon’s opinion. Only two studies on MB, one comparing the outcome of MB plus PPV in naïve and recurrent MHRD [23] and the other comparing MB with or without PPV [16], have been published to date. In the former, better anatomical results were obtained in naïve MHRD than in eyes previously treated with PPV. This may be because the decision to use both PPV and MB as the first surgical treatment simultaneously eliminated all the tangential and anteroposterior tractional forces that could lead to retinal redetachment [23]. Nonetheless, in the latter, the authors suggested use of MB alone as the first-line procedure for all eyes in which the posterior staphyloma was considered the leading cause of the tractional disorder, reserving the combined approach for eyes showing significant tangential traction on OCT, and as second-line surgery [16].

In the light of these results, the answer to the first question seems to converge on the same conclusion: MH closure is a crucial step to successfully treat MHRD and improve functional outcomes, particularly if vitreous surgery is the only surgical procedure applied [54,55,56,57]. Nevertheless, MB may help to avoid retinal redetachment in persistent MH.

The role of the axial length

As to whether the axial length may influence surgical outcomes, in the study of Nakanishi et al. [58], axial length was the only statistically significant prognostic factor for initial retinal reattachment in MHRD treated with PPV and gas tamponade. Three years later, in 2011, Suda et al. [59] documented a 73.3% MH closure rate after vitreous surgery in 15 highly myopic eyes. Nevertheless, the MH remained open in all eyes with axial length > 30 mm and 2 patients developed retinal detachment secondary to persistent MH. In a recent study by Nadal et al. [60], 27 eyes with MHRD were treated with PPV, ILM peeling, and silicone oil tamponade; retinal reattachment and MH closure rates were 85.1% (23/27) and 51.9% (14/27), respectively. After separating the series into subgroups according to axial length, the rates were 70 and 30%, respectively, in eyes with a length > 30 mm, and 94.1 and 64.7%, respectively, in those with a length < 30 mm, which yielded a significant difference. In a study by Arias et al. [61], 15 eyes with MHRD and axial length > 30 mm were treated with PPV and silicone oil tamponade: in 6, the MH was not primarily closed and in 2, macular detachment persisted. Taken together, these results seem to suggest that the effectiveness of PPV is limited when axial length is >30 mm. According to the analysis carried out in this review, when MB was used in eyes with a mean axial length > 30 mm [16, 17, 24,25,26, 29, 30], the retina was reattached in 100% of cases and the MH closure rate ranged from 40 to 100%. Interestingly, retinal redetachment was not observed in patients with a persistent MH in these studies. In this sense, MB seems to achieve better anatomical success rates than PPV.

The choice of the intraocular tamponade

However, axial length is only one factor to consider. The choice of vitreous tamponade especially during PPV for eyes with MHRD is another controversial issue. Uemoto et al. [62] reported higher retinal reattachment and MH closure rates with the use of perfluoropropane (C3F8) gas than with sulfur hexafluoride (SF6). In contrast, Nakanishi et al. [58] reported no significant differences in anatomical success rates after vitreous surgery depending on the type of gas tamponade. However, since the choice of gas tamponade and duration of face-down positioning are strongly surgeon-dependent, the possible influence of these factors on the anatomical outcome remains controversial.

Several authors have suggested that silicone oil (SO) should be preferred as intraocular tamponade, as it avoids the MH reopening that occurs after gas disappearance, thus improving the anatomical outcomes. SO is also reported to be an inductor and scaffold for glial closure of the MH, also facilitating faster absorption of residual subretinal fluid by the underlying RPE [63]. However, marked scleral irregularity such as that seen in highly myopic eyes was found to be associated with failure of both standard and heavy silicone oil (HSO) tamponades [64, 65]. Overall, retinal reattachment rates using SO during PPV range from 67 to 92% [66]. However, in the study of Qian and Jiang [67], the MH was closed in only 48.8% of patients after low-density silicone oil (LDSO) removal, with a final retinal reattachment rate of 38% in those with persistent MH.

When the patient is in an upright position, which is most of the time, the bubble of standard SO does not seem to conform to the foveal depression, resulting in a lack of effective tamponade over the macula. This may be the reason why various authors have suggested that HSO is a better tamponade for the foveal region. In the studies of Cheung et al. [68] and Avitabile et al. [69], high anatomical success rates were achieved with HSO, especially in comparison to those obtained with LDSO. But not all the results are consistent. Sandner et al. [70] documented recurrent MHRD in three of four patients primarily treated with HSO, suggesting that there was no additional effect on the posterior staphyloma with this heavy tamponade. The same results were obtained by Mete et al. [71], showing that standard SO and HSO seemed to be equally good surgical options, as there were no significant differences in the associated retinal reattachment rates.

Despite several advantages associated with SO use (hyperopic shift, transparency, longer tamponade, promotion of glial closure of the MH, and less or no need for face-down position), some studies on MB combined with PPV suggest that intraocular gas offers an effective tamponade for recurrent and previously untreated MHRD [16, 23].

Furthermore, it is well known that SO removal requires additional surgery, and that it may also lead to postoperative complications, such as secondary glaucoma [57] or retinal or optic disc atrophy [72]. In the study of Nishimura et al. [57], 18% of patients (4/24) who underwent SO removal after MHRD surgery required continuous use of antiglaucomatous drops, and one patient needed trabeculotomy because of refractory ocular hypertension. In the report by Mete et al. [71], chronic glaucoma developed in 23% of patients treated with PPV and SO tamponade.

In sum, whatever the endotamponade used, the main, unresolved issue is still MH closure. In this sense, only the episcleral macular approach has shown primary MH closure and retinal reattachment rates higher than 80% in most of the related studies [20, 23, 25, 26, 30]. In addition, the reported anatomical success rates were higher in eyes treated with a combination of MB and PPV, and there was no risk of retinal redetachment when MH closure was not achieved.

MFS group

Although a single term is used to refer to MFS, different types have been identified based on the imaging advances of OCT technology [45, 73, 74]. Even if MFS can remain stable for many years and in rare cases even resolve [75], the natural history of this condition is usually progressive. Evolution to posterior retinal detachment in the absence of MH or MHRD can also occur within a short time [76]. Thus, assuming that MFS is one of the three posterior staphyloma-related conditions and may represent the prior stage of MHRD [42,43,44,45], the aim of any surgical treatment, whether transvitreal or episcleral, should not differ from that advocated for MHRD; that is, to eliminate all the anteroposterior and tangential traction causing the condition. However, there is still controversy regarding what types of MFS are suitable for PPV or MB. Based on this review and as reported in Table 4, among 178 highly myopic eyes with MFS treated with MB, complete resolution of foveoschisis was achieved in 5 of 11 series, with foveal reattachment rates ranging from 66.6 to 100%. Concomitant PPV with or without ILM peeling was carried out in three studies and further vitreous surgery due to residual tangential traction after MB alone was performed in three patients in one study [16]. Recurrent MFS was observed in only 1 study [37] (3/178 eyes, 1.6%) and postoperative MH and MHRD developed in 1 eye each, in 2 different studies [30, 37]. Regarding functional outcomes, MB seems to provide good results demonstrating a visual improvement in 33.3 to 90% of MFS cases, including eyes with or without initial foveal detachment.

However, in addition to the anatomical success rates whatever the procedure as reported above, vitreoretinal surgeons have to face some other important issues when approaching MFS cases: (1) Can the ILM peeling be related with postoperative MH formation in case of PPV? (2) Can OCT scans be helpful to identify the appropriate timing for surgery in patients at a higher risk of rapid progression?

Although MFS is usually resolved with PPV also without ILM removal, it is well recognized that ILM peeling is the only way to completely remove all vitreous tractions on the retina surface and avoid cellular reproliferation, which can ultimately lead to recurrent MFS. Furthermore, peeling enables elimination of tangential traction while facilitating readaptation of the retina to the posterior eyewall, as occurs during resolution of foveoschisis. However, it should be noted that PPV with ILM peeling, which is widely performed in highly myopic eyes with MFS, can be associated with a higher risk of postoperative MH. If OCT scans document detachment with a thin inner roof in the foveal area, ILM removal can eventually break this roof, inducing a full-thickness MH [46]. To date, secondary MH occurred in 27.3 and 19% of cases after vitreous surgery both with and without ILM peeling, respectively [42, 47, 77, 78]. This is probably one of the main reasons why the usefulness of ILM peeling remains controversial and some authors have recently suggested that “sparing the fovea” could be an effective approach during ILM removal to minimize the risk of MH development [79, 80].

It is well known that patients affected by severe MFS with or without foveal detachment can still have good visual acuity over a lengthy period. Some authors have suggested that surgical and functional benefits are greater in patients with foveal detachment than in those with isolated MFS [73]. It seems reasonable that once any of OCT changes are observed (i.e., foveal detachment, lamellar holes, MH, etc.), high myopia patients should be closely monitored to plan surgical treatment as soon as vision rapidly decreases, in an attempt to prevent the final stage of MHRD. In other words, whatever the surgery, it should be both therapeutic and preventive. Taking into account this “double-duty,” OCT scans would be essential to identify patients at a high risk of progression, and should be included in follow-up visits.

Even if partial or complete resolution of MFS can be obtained with PPV, all these results seem to confirm that the inner retinal tension associated with MFS cannot be completely eliminated by vitreous surgery, since some of the components (i.e., vascular stiffness and posterior staphyloma) cannot be removed. In contrast, MB might help to release these tractions, especially in eyes at a high risk of rapid progression to MHRD, such as those with a thin foveal roof, outer lamellar holes, and severe foveal detachment on OCT scans. However, the lack of randomized comparative studies makes it difficult to clearly demonstrate whether the MB technique or PPV is superior for this condition.

MH-MFS group

When highly myopic eyes are affected by a combination of MH and MFS, the anatomical and functional results of treatment with PPV and ILM peeling seem less satisfactory than those of MB as shown in Table 4. In the study of Ikuno and Tano [46], primary MH closure was attained in only one of eight eyes (12.5%), and five patients underwent a second operation due to persistent MH, achieving a final closure rate of 25%. BCVA improved in 37.5% of cases. Interestingly, the authors reported that MH size significantly increased when closure was not achieved (75% of cases), suggesting that while trying to resolve the foveoschisis with vitreous surgery in this type of MHs, the retinal reattachment, itself, could force the inner retina to follow a larger arc made by the choroid/sclera, thus resulting in a MH enlargement. Two years later [73], the same authors reported a primary closure rate of 36% in another case series including 11 patients with MH-MFS. All unsuccessfully treated patients (n = 7) underwent a second surgical approach, but MH closure was only achieved in one (final closure rate, 45%). Visual acuity did not significantly improve. Based on these poor anatomical results, the authors postulated that ILM peeling and gas tamponade do not provide sufficient redundancy to the retina, and this could be considered a limitation of this type of surgery. They concluded that the MH closure rate in eyes with concomitant MFS was comparable to that of myopic MH with retinal detachment. In the last case series, published by Jo et al. [45], ten patients underwent PPV. MH closure was achieved in five (50%) and BCVA improved by more than three lines in only 20% of patients.

In summary, the MH closure rate never exceeded 50% following PPV, and further operations were often required. Furthermore, 37.5% of patients experienced no significant visual improvement. By contrast, when MB was performed alone or combined with PPV, MFS resolved and MH closure was achieved in 100% of patients, and more than 80% showed a final increase in visual acuity (Table 4). These findings seem to suggest that simple elimination of tangential and anteroposterior traction with vitreous surgery, without reshaping the posterior eyewall as MB does, may not suffice in many cases, especially in eyes with an axial length > 30 mm and/or with deep posterior staphylomas [55, 59]. Moreover, as was indicated in the MH-MFS case report by Ikuno and Tano [81], retinal detachment seems more likely to develop in persistent MH, but it occurs very rarely in emmetropic eyes and in myopic MH without foveoschisis. In other words, it is suggested that MH-MFS represents a stage prior to retinal detachment secondary to MH [74], and moreover, progressive axial length or foveal detachment (or both) may prevent MH closure in these eyes [55].

Furthermore, several types of staphylomas with different depth and features and which could lead to stronger or weaker anteroposterior traction have been described in literature [41, 82]. Some degree of neuroretinal splitting may occur in association with “deep” staphylomas, since the retinal elasticity is limited by the ILM [83] and retinal vessels [48]. As a consequence, myopic foveoschisis may develop and it can remain stable for years or progress to MH and secondary posterior retinal detachment [44]. On the other hand, anteroposterior traction may be weaker in “flatter” myopic staphylomas, without leading to separation of the intraretinal layers. Interestingly, only 39 of the 489 eyes (7.9%) included in this review were affected by MH-MFS, thus suggesting, once again, that when MH and MFS are simultaneously present, they quickly progress to MHRD.

Additional concepts, future perspectives, and conclusions

Despite the common rationale for all macular exoplants (i.e., to reshape the posterior eyewall and reduce retinal traction), they probably do not all act in the same way. Some may induce excessive compression under the choroidal vessels and cause RPE changes and serous foveal detachment [84] while others do not. When this occurs, the shape of the indenting head, which probably affects blood flow in the choroidal vasculature, has been proposed as the leading cause. However, RPE disturbance has also been reported after PPV without MB in highly myopic eyes [85], suggesting that further mechanisms may be involved.

All buckles using a nasal-to-nasal approach can induce muscle injury and vortex vein damage, which can lead to choroidal detachment in severe cases. Moreover, some techniques may be associated with a higher risk of complications than others, and be more challenging because of technical difficulties while placing the exoplant.

One of the most innovative advances in the MB technique is suprachoroidal injection of long-acting hyaluronic acid [25]. The main advantage of this strategy seems to be the ability to indent the macular area without directly compressing the posterior vessels, thereby reducing the risk of secondary RPE atrophy. However, there may be some difficulties in correctly placing the injection and delivering sufficient volume when addressing a complex, deep posterior staphyloma. Another factor to considered is the temporary effect of hyaluronic acid, even when chemically modified (cross-linked) to make it last longer under the macula; hence, the indenting effect could be reversible. Nevertheless, some studies have shown that for whatever the reason, when the MB is removed in MHRD eyes, the MH remains closed and the retina attached, suggesting that permanent indentation may not be crucial. Despite its promising results, much longer time and experience are needed in order to incorporate the suprachoroidal injection of long-acting hyaluronic acid in the methods of macular hole closure in eyes with high myopia.

Determining whether there is room for further surgical possibilities in this scenario may also be a challenge.

Innovations often need an extra push, and another promising new stimulus in this regard is the development of OCT-assisted surgery. Intraoperative, real-time OCT (iOCT) can improve identification and removal of premacular tractions during PPV, and facilitate placement of any MB under the macular region in terms of height and position. OCT study has shown that some MHs remained open despite retinal reattachment, perhaps because of excessive or insufficient posterior indentation [24, 29, 43]. Direct visualization of a thin or thick roof in MFS visualized by iOCT could help guide vitreoretinal surgeons in the choice of whether and how to perform ILM peeling in PPV, to minimize the risk of iatrogenic MH [42, 78].

Thus, the main question “Do all posterior staphylomas act in the same way?” seems to have found an answer in several published studies, which indicate that “No, actually, they do not.” And this leads to a final query: “If all this research confirms that myopic traction maculopathy is a posterior staphyloma-related condition, is PPV enough to solve the problem?” In eyes with a posterior staphyloma deep enough to induce progressive retinal stretching, and potentially leading to MFS or MHRD, when the retina detaches, the inner and outer retinoschisis tends to decrease only in the detached retina, suggesting that relief of strong anteroposterior traction is likely more related to the posterior staphyloma than to the vitreous cortex. Indeed, several OCT images of MHRD and MFS with foveal detachment clearly illustrated this phenomenon [31, 42, 44, 74]. Regardless of whether the MHRD originates from MFS with foveal detachment or MH with concomitant foveoschisis, the conclusion seems the same: these are posterior staphyloma-related conditions in which the eyewall tends to extend posteriorly. Therefore, PPV may provide good postoperative results, but is likely insufficient to be considered the best surgical approach for these cases. However, the combination of PPV with MB as the first-line surgical treatment can definitively eliminate all tangential and anteroposterior tractions, and likely improve the final anatomical and visual outcomes.

In contrast, in highly myopic eyes affected by MH without foveoschisis, a surgical technique similar to that used in non-myopic cases (PPV, ILM peeling, and intraocular tamponade with gas or silicone oil) [76], should be effective to achieve a high MH closure rate without the need of posterior buckles [26].

To date, there is still no general consensus on the ideal timing for surgery or the most appropriate surgical treatment, and the discussion seems far from being closed. The lack of easily available macular buckles and the common idea that the surgery is highly complex are major obstacles for vitreoretinal surgeons managing high myopic patients. However, this review has shown a generally low rate of complications. Specifically, one of the main complications of macular buckle seems to be the occlusion of the choroidal vessels due to the extensive compression exerted by the exoplant that lead RPE changes including atrophy in some cases (> 2.4%), followed by MB removal (2%), malpositioning requiring surgery (1.8%), and choroidal effusion (1.4%). Scleral perforation, commonly considered one of the main risks because of the scleromalacia typical of these eyes, was described in only 7 of 489 cases (1.4%).

Despite 16 years of results have been carefully reviewed, we are conscious about the limitations of this study. The lack of a statistical analysis does not avoid the presence of both selection ad subjective bias which might be related to the authors interpretation and conclusions. However, being a “narrative” review, a systematic analysis of all published data might not be strictly required without preventing this work to be equally evidence-based or clarifying. Ideally, the analysis of the results of PPV and MB separately or combined for MHRD, MFS, and MH-MFS should have been presented systematically. However, many of these case series do not distinguish between the three different pathologies in which the MB technique is applied and results are often mixed up, cumulative, and heterogeneous within the same study. It is opinion of the authors that this could prevent vitreoretinal surgeons to clearly understand whether and which of these three high myopia-related conditions might take advantages by this technique, if any. In light of all these reasons, we strongly believed that both anatomical and functional results in these three different subgroups should be analyzed separately to make this review as homogenous as possible.

Conclusions

Although several approaches are used for MB surgery [86–88], the anatomical and functional results tend to be similar within groups of patients having similar conditions. Concomitant resolution of foveoschisis, retinal reattachment, and MH closure seemed to be achieved more frequently with MB than PPV, particularly in those eyes with greater axial length, in which MH closure is rarely obtained after vitreous surgery. The presence of a deep posterior staphyloma and a persistent MH after PPV should be considered the two main risk factors for retinal detachment in highly myopic eyes. Overall, additional surgeries are less commonly required when MB is applied, alone or associated with PPV. As to the best intraocular tamponade for PPV, there is no broad consensus, and gas or silicone oil are both widely used, especially for MHRD. However, when PPV is combined with MB, gas tamponade is usually considered safe and effective without the risk of secondary glaucoma due to silicone oil. In sum, currently, the MB technique seems to be the most effective surgical approach to counteract the pulling effects exerted by the posterior staphyloma, since it appears as the only strategy to convert the posterior shape of the eye from a concave form into a more flat or similar-to-natural shape relieving the anteroposterior tractions which lead to the myopic tractional maculopathy.