High Myopia and the Vitreoretinal Complications

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Chapter 113 High Myopia and the Vitreoretinal Complications

Yasushi Ikuno, Masahito Ohji

Introduction

The incidence of high myopia varies among ethnic groups, races, and countries, but there is a higher incidence in Asian countries. Some of the incidence rates worldwide range from 1% in Black Americans,¹ 2% in Caucasian Americans,¹ 2.6% in Chinese individuals,² to 5.5% in Japanese individuals.³ The prevalence of myopia seems to be increasing,⁴ and it is one of the major causes of visual impairment, especially in Europe and Asia.^5,⁶

The definitions of high myopia vary slightly; however, there is agreement that the spherical equivalent refractive error exceeds −6 diopters (D) and/or the axial length is longer than 26.5 mm. Pathological myopia is defined as high myopia with any posterior myopia-specific pathology resulting from excess axial elongation. Pathological myopia is characterized by posterior staphyloma formation. Pathological myopia also is associated with specific macular complications such as choroidal neovascularization and chorioretinal atrophy. Myopic foveoschisis and macular holes with or without retinal detachment are also specific to myopia and major indications for surgical intervention.

Observation of a myopic macular area using a contact or non-contact lens has been challenging because the atrophy lowers the contrast. This has hindered detailed observation and consequent understanding of the pathophysiology, although myopia-specific macular diseases have been well known for a long time. Technologies such as optical coherence tomography (OCT) have facilitated both visualization of the retinal microstructures in pathological conditions and an understanding of the pathogenesis, interaction, and disease progression. This information has led to revolutionary changes in the disease concept of myopia-specific macular diseases. Pathological myopia is now a much more accessible disease than it was 20 years ago.

Examiners often have difficulties obtaining clear and high-contrast OCT images in highly myopic eyes. The characteristics of the OCT image in these eyes are: (1) a relatively low signal to noise ratio; (2) deep posterior staphyloma in the presence of which the peripheral tissue often drops off from the top edge of the image; (3) poor fixation due to a large central scotoma from chorioretinal atrophy; and (4) critical signs that are mostly outside the fovea. The pearls for the OCT examination are as follows. First, it is much better to use spectral domain (SD-) OCT, which provides much higher sensitivity and scanning speed than time domain (TD-) OCT. TD-OCT is acceptable; however, micropathologies such as small macular holes or columns (glial thin tissue bridging the inner and outer retina in the area of retinoschisis) that are clearly depicted in SD-OCT images might be overlooked. Second, the pathology of interest must be located near the top of the OCT image. SD-OCT has the strongest signal at the top and the weakest at the bottom because of the so-called signal decay. This procedure maximizes the signal and enhances the contrast of the pathology being targeted. Third, large internal fixation or external fixation must be used to avoid unnecessary ocular movement in cases with a large central scotoma. Finally, attention must be paid to pathologies outside the fovea. For instance, a small macular hole is sometimes outside the fovea,⁷ and other micropathologies such as retinal vascular microfolds, internal limiting membrane detachments, and paravascular microholes are sometimes far outside the macula. The use of the 5-raster scan has a significantly higher rate of detection of these pathologies than the use of a single B-scan alone.⁸ The use of raster or grid scan is highly recommended to understand all of these micropathologies.

Imaging technologies have identified myopic foveoschisis, which is a relatively new pathology that was recognized about 10 years ago.⁹ It is now generally agreed that this pathology is not uncommon in highly myopic eyes, and myopic foveoschisis is regarded as a precondition for development of a macular hole and retinal detachment. OCT studies of myopic foveoschisis have revealed many preclinical and pathological conditions underlying the myopic–macular diseases, as discussed below. This information is also helpful for understanding the process and pathophysiology of macular holes and retinal detachments, which are the most problematic complications for vitreoretinal surgeons. In this chapter, we review the recent studies and shed light on the vitreoretinal complications of high myopia.

Retinal detachment from peripheral breaks

Retinal detachments from peripheral retinal breaks are common in high myopia. The prevalence of any type of retinal detachment increases in association with the degree of negative refractive error.¹⁰ The distribution of high myopia exceeding −6.0 D is about 16% in overall cases and the lifetime risk is more than 20-fold compared with emmetropia.¹¹ In addition, the onset of retinal detachment is at a younger age, based on the degree of myopia.¹¹ The frequency of retinal peripheral degeneration increases along with the axial length.¹² The development of posterior vitreous detachment (PVD) according to the higher liquefaction of the vitreous body occurs at a younger age in eyes with severe high myopia.¹³ These facts seem to account for the increased prevalence of retinal detachment.

A rhegmatogenous retinal detachment (RRD) must be treated with a scleral buckling procedure or vitrectomy combined with gas or silicone oil tamponade, as for non-highly myopic retinal detachment. Scleral buckling is the first choice for retinal breaks with non- or minimal vitreous traction and vitrectomy for significant traction from the vitreous. We normally use a 25-gauge system for vitrectomy, and a small-gauge system works well in cases of high myopia; however, the special conditions in highly myopic eyes must be understood.

The first factor to keep in mind is the thin sclera, which increases the risk of perforation when the mattress suture for buckling is passed inside the sclera. The surgeon must put a mattress suture where the sclera is sufficiently thick. Scleral thinning is identified by the presence of a blue sclera. A thin sclera also hinders self-sealing of the wound in small-gauge vitrectomy surgery. The self-sealing is harder to obtain due to creation of a shorter scleral tunnel even with oblique (angled) entry. Therefore, maximal care must be taken to lengthen the scleral tunnel. Two-step entry (angled then perpendicular) is recommended for good wound construction. Persistent wound leakage and consequent hypotony increase the risk of postoperative complications, including bacterial endophthalmitis.

Another important factor is that highly myopic eyes have a large vitreous cavity, which requires a greater volume of aqueous humor production to maintain the intraocular pressure (IOP). Therefore, postoperative hypotony (especially in an early phase) is more often seen in highly myopic eyes. Postoperative hypotony increases the risk of choroidal hemorrhages, and high myopia is a high-risk factor for this complication. Hypotony also hinders self-sealing of the wound.

The IOP must be set higher than usual at the end of the surgery for highly myopic eyes to maintain good postoperative rigidity. This is necessary not only to avoid IOP decreases before the recovery of aqueous humor production but also for enhancing the self-sealing of the wound. In addition, if gas or fluid leakage from the sclerotomy site is seen, the surgeon must consider placing a suture. If hypotony develops on day 1 after surgery, the surgeon must ascertain that there is no wound leakage and no signs of infection. If the wound is sealed, the IOP usually returns to normal in a few days.

Epidemiology of surgical macular complications

The incidence rates of myopia-specific macular complications such as myopic foveoschisis and macular holes with or without retinal detachments have not been well documented, because these complications are rare. Myopic foveoschisis was identified in 9% of patients with posterior staphyloma.¹⁴ In patients with a macular hole and retinal detachment, 8.5% develop the same pathology in the fellow eye within 4 years.¹⁵

Rhegmatogenous retinal detachment after refractive surgeries

Rhegmatogenous retinal detachment is a major complication after refractive surgeries. The incidence is not as high after laser in situ keratomileusis and was reported to be 0.25%¹⁶; however, it is much higher after refractive lens exchange, reportedly 7.3% within 3 years¹⁷ and 8.1% in 7 years.¹⁸ Retinal detachment is a rare but general complication after cataract surgery, with incidence rates of 0.93% in the general population¹⁹ and 2.2% after phacoemulsification in highly myopic eyes.²⁰ A high likelihood of PVD occurring within 5 years after surgery²¹ seems to be associated with a higher incidence.

Etiology and pathophysiology

Myopic foveoschisis

Myopic foveoschisis is characterized by retinoschisis with or without localized retinal detachment and is specific to high myopia. This pathology was identified recently (Fig. 113.1).⁹ Myopic foveoschisis is also referred to as a posterior retinal detachment without a macular hole in highly myopic eyes, described by Phillips in 1958, who reported a case with a retinal detachment within posterior staphyloma but no apparent macular hole.²² Perhaps some patients might have this pathology; however, it is difficult to rule out small macular holes or paravascular microholes. The detailed pathology and its mechanism awaited the development of OCT for decades. Takano and Kishi examined 32 highly myopic eyes with OCT and found retinoschisis in nine eyes and a foveal detachment in one eye, suggesting that retinoschisis and foveal detachment are not uncommon in highly myopic eyes.⁹ It has been reported that myopic foveoschisis is characterized by variations in the foveal architecture, including a foveal cyst in 47%, a lamellar hole in 29%, and a foveal detachment in 29%.²³

Fig. 113.1 Typical appearance of myopic foveoschisis. The fundus photograph (inset) shows a slightly elevated retina at the posterior pole, although it is not visually apparent. A horizontal optical coherence tomography scan involving the macula shows retinoschisis in multiple retinal layers and a retinal detachment at the fovea (asterisk). There is glial tissue bridging the inner and outer layers of the retinoschisis (a so-called column; arrow).

The pathogenesis of myopic foveoschisis has been disclosed recently. Various OCT images from these myopic eyes have led to the hypothesis that the inner retina is less flexible than the outer retina.²⁴ Factors limiting the inner retinal flexibility include the vitreous cortex adhering to the retina, epiretinal membranes (ERMs), internal limiting membrane (ILM), and retinal vessels. Preretinal membranes, which can be hard to recognize clinically and are found only at the microscopic level in highly myopic eyes,²⁵ cause deterioration in the retinal flexibility.

Histologic studies have shown retinoschisis at multiple levels in the outer plexiform layer, inner plexiform layer, ganglion cell layer, and nerve fiber layer.²⁶ There also is a preretinal fibrous membrane. The retinoschisis is bridged and a lamellar hole sometimes can be observed in the foveal region. An electron microscopic study on excised ILM samples during vitrectomy has shown that collagen fibers and cell debris were present on the inner surface of the ILM in 70% of the myopic foveoschisis, substantially more than that found in idiopathic nonmyopic macular holes (0%).²⁵ Moreover, more fibrous glial cells were likely to be found on the inner surface of the ILM.²⁶ Microvascular traction can be seen as arteriolar separation from the retina.²⁷

ILM detachments, sometimes recognized as “inner retinoschisis,” are often seen in highly myopic eyes, which explains the underlying traction from the ILM on the other retinal layers (Fig. 113.2).²⁸ Inner retinal elevations along with retinal vessels recognized as tent-like lesions on OCT images, so-called retinal vascular microfolds, are observed especially in vertical sections (Fig. 113.3).²⁹ This finding represents traction from the vessels on the retinal surface. A large OCT study of 200 highly myopic eyes reported a 6% incidence of ILM detachments, a 13.5% incidence of retinoschisis, and a 20% incidence of retinal vascular microfolds.³⁰ These components generate inward tractional force on the inner retina, which potentially splits the retina, causing retinoschisis and finally leads to a retinal detachment at the fovea.

Fig. 113.2 Representative optical coherence tomography appearance of an internal limiting membrance (ILM) detachment (arrows) in highly myopic eyes. The ILM layer is detached from the other retinal layers.

Fig. 113.3 Representative optical coherence tomography appearance of retinal microfolds (arrow) in highly myopic eyes. This microfold is associated with the retinal vessels and warrants microvascular traction on the retina.

Macular hole with or without retinal detachment

Retinal detachments from a macular hole are a typical complication in highly myopic eyes. The vitreous cortex adhering to the retinal surface around the hole causes tangential traction that generates an inward vector component in deep staphyloma in highly myopic eyes, resulting in a retinal detachment.³¹ Releasing the retinal traction is critical to successful reattachment; thus, vitrectomy with vitreous cortex and membrane removal is effective.³¹ Physicians sometimes observe macular holes without a retinal detachment,³² indicating that macular hole formation does not always lead to retinal detachment and that there might be two distinct types of macular holes in high myopia. A recent OCT study reported that persistent traction at the macular hole edge after opening is critical for initiating a retinal detachment.³³ A macular hole with retinoschisis has a higher likelihood of progressing to a retinal detachment than those with a retinal cyst, resembling idiopathic non-myopic macular holes (Fig. 113.4).

Fig. 113.4 Optical coherence tomography appearance of two distinct subtypes in highly myopic macular holes. (A) A macular hole with surrounding retinoschisis usually presents a higher likelihood of consequent retinal detachment, while (B) a macular hole without retinoschisis has only retinal cysts and is normally stable.

A macular hole with retinoschisis typically presents with deeper posterior staphyloma, which explains the lower anatomic success rate in this subtype.³³ Deep posterior staphyloma generates a larger vector component from the tangential traction exerted by the ERM or the ILM, which acts on the retina as an inward tractional force. This is why the retinoschisis is present in the retinoschisis type. In addition, with deep staphyloma it is more difficult to close the macular hole because of excess stretching in the retina. While shallower posterior staphyloma generates less tractional force and the retina is flat as seen in non-myopic eyes. This flat configuration exerts less stretching in the retina, and, thus, there is a higher likelihood of macular hole closure. The type of macular hole is highly dependent on the depth of the posterior staphyloma and underlying tractional force, which affect the anatomic success rate. OCT observation of the macular hole edge provides one clue to the prognosis.³³

In highly myopic eyes, multiple components adhere to the retinal surface in most cases and are often recognized during vitreous surgery. Electron microscopic studies have shown that they are the vitreous cortex, cellular ERMs, and ILMs,³⁴ suggesting that complete removal of these tractional forces is essential in reattachment surgery.

Posterior retinal detachments from paravascular microholes

Retinal detachment from a paravascular microhole is also specific to highly myopic eyes (Fig. 113.5). Microholes are typically small, round or oval retinal holes associated with posterior major vessels.³⁵ There are sometimes multiple holes that are adjacent to the major vessels. An OCT study of highly myopic eyes reported that the incidence rates of retinal cysts and paravascular holes were 50% and 27%, respectively.³⁶ The vitreoretinal adhesion is often strong at the paravascular region, and traction from the vitreous at the site is believed to be a main cause of retinal rarefaction, resulting in retinal cysts and breaks.³⁷ Paravascular microholes often colocalize with vascular microfolds and retinoschisis,^8,²⁹ suggesting a close relationship with the retinal vascular traction.

Fig. 113.5 Intraoperative view of paravascular microholes in a highly myopic retinal detachment. Multiple, small and round retinal holes are located along the retinal vessels of the temporal arcade (arrows). A, retinal superotemporal artery; V, retinal vein.

Symptoms of myopic foveoschisis and macular holes with or without retinal detachments

Myopic foveoschisis and macular holes with or without retinal detachments typically occur in highly myopic, middle-aged to older women. In the authors’ clinic, 44 of 52 patients were women during the period 2000–2005.³⁸ Patients are normally aware of central visual distortion if they have only retinoschisis and a relative central scotoma corresponding to the involved area when the retinal detachment starts. Patients may be aware of an absolute scotoma at the center of the relative scotoma when a macular hole opens. Patients also report visual loss at the involved area if an extensive retinal detachment is complicated. Even if patients present with a macular hole, the Watzke–Allen test is usually negative.

Clinical findings

Myopic foveoschisis can be recognized as a slight elevation of the posterior retina in highly myopic eyes; however, it is difficult to accurately diagnose without OCT, especially in an atrophic fundus. OCT and other imaging tools are essential for complete assessment of the retinal status for surgical decision-making, e.g. to determine the presence/absence of retinoschisis and the area of retinoschisis or retinal detachment. This information is essential for surgical planning. For instance, if there is a foveal detachment found on OCT images, macular hole formation is likely to start in the near future, and surgery must be planned soon (normally within 1 or 2 months). However, if the patient presents with only retinoschisis but not a foveal retinal detachment, the surgery is not as urgent. Diagnosing a macular hole is also difficult in high myopia, especially in cases with an attached retina. OCT also facilitates assessment of the presence/absence of the hole and its size.

Optical coherence tomography features

Myopic foveoschisis presents with retinoschisis in multiple retinal layers. The split retinal layers normally have a bridge between them, the so-called column, which is presumed to be residual Müller cells (Fig. 113.1). In cases with a very atrophic retina, it can be difficult to distinguish retinoschisis from a retinal detachment, and the presence of the column is an important clue for diagnosing retinoschisis but not a detachment. Tracing the junction of the inner segment and outer segment (IS/OS) line of the photoreceptors is also useful for differentiating a retinal detachment from retinoschisis as shown in an early OCT study.³⁹ ILM separation from the other retinal layers also is observed, i.e., a so-called ILM detachment, and is an indicator of the tractional force from the ILM.²⁸ The tent-like peak of the inner retina is observed on the OCT image. This is coincident with retinal vessels, and the so-called retinal microvascular traction.²⁹ Because the retinal vessels normally run horizontally around the macular area, there is a higher chance of finding this in a vertical than a horizontal section because of the higher chance of observing a cross-section of the retinal vessels. The IS/OS junction line of the photoreceptors sometimes disappears in the area of the retinal detachment⁴⁰; however, the IS/OS junction line is typically well preserved in the area of retinoschisis, suggesting that the photoreceptor function is well preserved in this subtype.

Macular hole formation associated with retinoschisis has two stages (Fig. 113.6).³⁶ The first stage is the development of the so-called retinoschisis type, in which only retinoschisis is present and not a retinal detachment. Several months (sometimes several years) later a retinal detachment begins around the fovea. This stage is the so-called foveal detachment type, and a retinal detachment involving the fovea and retinoschisis around the macula are present. After a while, the inner retina above the detachment is stretched and torn. This is how a macular hole appears as a consequence of retinoschisis with a retinal detachment. Small macular holes are often difficult to visualize in a B-scan image, because the fixation point has shifted.

Fig. 113.6 Two distinct subtypes of myopic foveoschisis. (A) The retinoschisis type is characterized by only retinoschisis without a retinal detachment. (B) The foveal detachment type is characterized by a small localized retinal detachment, and the inner/outer segment line is separated from the retinal pigment epithelium. The retinoschisis type develops before the foveal detachment type.

The edge of a macular hole provides valuable information. As discussed previously, there are two types of macular holes in highly myopic eyes.³³ One is similar to an idiopathic macular hole, as normally seen in non-myopic eyes (Fig. 113.4B). In these, the edge of the hole is thickened with retinal cysts. There is no retinal detachment around the hole clinically, and this type usually does not progress for months or years. The other type has surrounding retinoschisis instead of retinal cysts around the hole (Fig. 113.4A). This type of macular hole results from myopic foveoschisis and can be considered a transition from foveoschisis to a macular hole with a retinal detachment. This type of macular hole typically progresses rapidly and is likely to complicate the retinal detachment because of underlying traction (see Etiology and pathophysiology, above). The typical OCT appearance of this type is characterized by a relatively high and rectilinear wall of the macular hole edge with an acute angle to the RPE line, and a sharp-angled edge of the top of the macular hole.³³ Therefore, observing the macular hole edge is essential for exact diagnosis, which is critical for decision-making and planning of the vitreous surgery.

Fundus autofluorescence

Fundus autofluorescence stimulates emission of light from the lipofuscin accumulated in the RPE and is an indicator of the oxidative stress level.⁴¹ Fundus autofluorescence also indicates the functioning of the RPE. In the atrophic fundus in myopic eyes, fundus autofluorescence helps distinguish the retinal detachment from the retinoschisis, because loss of the contact between the photoreceptors and the RPE results in hypoautofluorescence.⁴² This hypofluorescent area indicates the area of the retinal detachment and is a good indicator for monitoring its progression.

Treatment of foveoschisis

The natural course of myopic foveoschisis is unfavorable. Investigators have reported that the vision decreased in 69% of patients, a macular hole developed in 31% after 3 years of follow-up,⁴³ and in 50% of patients with retinoschisis a macular hole or retinal detachment developed after 2 years.⁴⁴ These observations encourage surgery to treat myopic foveoschisis as prophylaxis to prevent macular holes with consequent development of a retinal detachment.

Surgical indications

Myopic foveoschisis is sometimes asymptomatic, especially in cases with simple retinoschisis and no retinal detachment. Those cases are not good indications for vitreous surgeries. Even though patients are aware of a visual disturbance, turbulence, or visual loss, surgery can be postponed until the vision decreases to about 20/40 because there is still a chance of visual worsening after vitrectomy. The chance of visual improvement after surgery is about 80% in cases with a foveal detachment and 50% with retinoschisis alone.⁴⁵ The chance of visual improvement is substantially smaller if a macular hole is present before surgery,^45,⁴⁶ which is partly because macular holes have a poor closure rate after surgery. Hence, surgical intervention before macular hole formation is considered beneficial, although there is not yet strong evidence for this. The best indications for preventing macular hole development in these cases, are the presence of the foveal detachment type, moderate and severe visual loss, and high retinal detachment. These manifestations are typical and high risk for macular hole formation.

A localized retinal detachment in the posterior staphyloma from the macular hole often develops; however, there may be surgical benefits only in selected cases. This type of detachment is sometimes stable and does not progress. The retina is detached from the RPE and follows the minimal distance bridging the posterior staphyloma edge on the opposite site, which maintains balance and compensates for the retinal traction. Surgery can be postponed if the retinal detachment does not extend beyond the border of the staphyloma, and its progress should be monitored with OCT and/or fundus autofluorescence (see Fundus autofluorescence, above). The surgery should be performed as soon as possible if the situation progresses, because patients are at risk of total visual loss.

A macular hole with an extensive retinal detachment is a good indication for surgery. The surgical goal is to remove the entire component that is generating the tractional force on the retina and causing a detachment, including the vitreous cortex, ERMs, and the ILM. However, sometimes the traction persists from the retinal vessels even after a complete vitrectomy, leading to recurrence of the retinal detachment. Treating the posterior staphyloma is theoretically required for these cases and placing a macular buckle might be considered. Simple gas injection was attempted in an early case series especially for eyes with a PVD; however, this procedure cannot relieve the traction exerted by ERMs, for instance. Therefore, the expectation for anatomic success is not as high as that associated with vitrectomy with complete removal of any traction.⁴⁷

Surgical prognosis

The retina usually reattaches to the retinal pigment epithelium (RPE) slowly after the surgery (Fig. 113.7). The visual outcome associated with myopic foveoschisis is favorable if no macular hole develops. We reported that a substantial visual gain was achieved after vitrectomy in either group and that the final vision was similar between the foveal detachment type and the retinoschisis type; however, the visual change was significantly greater in the foveal detachment group than in the retinoschisis group.⁴⁵ Another study reported a similar trend and showed that 70% of eyes with a foveal detachment had a significant visual improvement compared with 42% in the retinoschisis group.⁴⁸ Once a macular hole develops, the hole is hard to close after vitrectomy. The macular hole closure rate with retinoschisis or retinal detachment ranges from 30% to 50% on OCT images.^46,⁴⁹ The macular hole closes in most cases^32,³³ without retinoschisis or a detachment. The postoperative visual level varies depending on the degree of the chorioretinal atrophy. The mean visual acuity was below 20/200, and the initial reattachment rate was about 70% after vitrectomy.⁵⁰ A longer axial length is generally a poor prognostic factor.^50,⁵¹ Macular buckling can compensate for any tractional force. For this reason, a comparative study showed a slightly higher initial reattachment rate than vitrectomy alone (90% versus 70%).⁵²

Fig. 113.7 Optical coherence tomography (OCT) appearance of a patient who underwent vitrectomy with internal limiting membrane (ILM) peeling and gas tamponade for myopic foveoschisis in Figure 113.6 (lower panel, foveal detachment type). (A) OCT image 2 months after surgery shows flattening of the retina. (B) An OCT image at the same position, 6 months after surgery shows that the retinoschisis has resolved; however, there is still substantial subretinal fluid. (C) An OCT image 12 months after surgery shows complete resolution of the retinal detachment.

Surgical procedures

Vitreous separation

A 25-gauge vitrectomy system is the first-line treatment for highly myopic eyes. No encircling band is required for this surgery. The vitreous plays an important role; therefore, creating a PVD is critical for reattaching the retina. The vitreous tightly and extensively adheres to the retinal surface in highly myopic eyes. Use of triamcinolone acetonide is essential for visualization and to identify residual cortex. To create posterior vitreous separation, a vitreous cutter and silicone-tipped backflush needle with active suction are normally used. A diamond-dusted membrane scraper ⁵³ is another option for an extremely thin vitreous cortex. The vitreoretinal adhesion is normally extremely tight around the optic nerve disc, and, therefore, the surgeon might consider starting temporally where the adhesion is normally the weakest. Importantly, great care is needed to separate the vitreous at the macula, because the macula is tightly adhered to the vitreous; placing stress on the macula may lead to macular hole formation. This procedure is difficult to perform in the detached retina, and a bimanual technique can be considered for a safe separation.

Internal limiting membrane peeling

The necessity for ILM peeling remains controversial in myopic foveoschisis, and one group reported a high success rate even without this procedure.⁵⁴ However, the ILM is separated from the other retinal layers on OCT images in most eyes,²⁸ suggesting that rigidity of the ILM plays a major role in this pathology. This fact warrants the necessity of ILM peeling for myopic foveoschisis at least in selected cases.

ILM peeling also can enhance macular hole closure and remove any traction on the retina in myopic macular holes with a retinal detachment,⁵⁵ and this raises the initial success rate.^51,⁵⁶ Indocyanine green was used to stain the ILM in the initial case series; however, it remains in the eye for longer than 6 months postoperatively.⁵⁷ Brilliant Blue G can selectively stain the ILM and is less toxic.⁵⁸ This might be a useful option.

Tamponade

In cases of macular holes with or without a retinal detachment, gas tamponade must be performed at the end of surgery. Long-acting gas tamponade (i.e., perfluoropropane) must be used because it has a higher anatomic success rate.⁵⁹ Because there is no coagulation maneuver around the macula, it is critical to support the retina for a long time to recover the integrity between the RPE and photoreceptors in atrophic eyes. Silicone oil tamponade is also an effective option.⁶⁰ The use of heavy silicone oil is reportedly effective as well.⁶¹

Macular buckling

In cases of recurrent retinal detachments, placing a buckle can be considered to fix the dimensional abnormality of the posterior staphyloma. Direct macular buckling was attempted in the initial cases; however, the modified silver clip ⁶² method seems to be commonly used. The superotemporal conjunctiva is cut down and a mattress suture placed to fixate the top of the buckle. The indented part is on the other side. The arm is adjusted to fit the scleral curve so that the tip of the buckle reaches the macula.

Macular buckling reportedly has a higher success rate for retinal reattachment than vitrectomy,⁵² likely because of the change in the vector force. Tangential traction generates the inward vector force in the posterior staphyloma, which is concave in shape. Macular buckling changes the macular area to a convex shape, and the vector force changes in direction to reattach the retina. Therefore, macular buckling is supposed to provide stronger contact between the neural retina and the RPE.

However, metamorphopsia and disruption of the choroidal circulation with protrusion of the posterior pole are the major concerns after macular buckling surgery. This maneuver is associated with a learning curve for placing the tip at the macula because it is a blinded procedure.

The authors normally perform vitrectomy as the first-line treatment for macular holes and retinal detachments and attempt to remove all tractional force from the vitreous cortex, ERMs, and ILMs and long-acting gas or silicone tamponade. This technique is associated with a success rate of approximately 70–90%. However, if the retina detaches again because of macular hole reopening, macular buckling is performed, since another vitrectomy would not work well. Thus, the authors regard this procedure as rescue surgery for redetachment cases.

Postoperative complications

Opening of a macular hole occurs in less than 5% of patients who undergo vitrectomy for myopic foveoschisis.^45,^48,⁵⁴ Cases in which ILM peeling was performed in the presence of an extremely thin, stretched fovea are at risk of developing this complication. Attention must be paid to detecting any small macular holes before vitrectomy, because the holes are normally stretched and enlarged postoperatively. Simply using a long-acting gas injection is not well accepted for postoperative macular holes, because this complication results from a shortage of retinal redundancy. Reoperation and removing any residual traction might be useful.⁶³

Recurrence of a retinal detachment is a major postoperative complication after vitrectomy performed to treat a macular hole with a retinal detachment. Removing residual vitreous cortex and ERMs is critical during a reoperation. However, it is sometimes difficult to identify the apparent cause of a redetachment. In those cases, persistent traction, such as microvascular traction, is responsible. Macular buckling is essential in those cases.