Myopic foveoschisis is characterized by retinoschisis and subsequent retinal detachment specific to highly myopic eyes. Myopic foveoschisis was first described in the 1950s (Phillips 1958) and was so common as to be found in 10 of 32 highly myopic eyes (Takano and Kishi 1999). However, this pathology is challenging to diagnose correctly without OCT. Myopic foveoschisis is substantially a tractional disease that is generated from various components. The vitreous cortex is one causes of the inward retinal traction. ERMs often develop and also generate traction. The rigidity of ILMs and the retinal vascular traction are unique and both are new idea of pathogeneses. ILM detachment from the other retinal layer often is observed on OCT images (Sayanagi et al. 2006) (Fig. 22.3). This indicates that the ILM is less flexible than the other retinal layers and exerts inward traction on those layers. Retinal vascular traction is postulated based on a unique OCT finding, i.e., retinal microfolds (Ikuno et al. 2005; Sayanagi et al. 2005). The retinal microfolds appear on OCT images as small peaks in the inner retina and are typical findings after vitrectomy performed to treat myopic foveoschisis (Fig. 22.4). The retinal vessels, especially the retinal arterioles, are less flexible and cannot be stretched as much as the other retinal components. Thus, myopic foveoschisis is caused by multiple factors and can be regarded as a split between the flexible outer retina and the inflexible inner retina.

OCT has demonstrated a more detailed mechanism related to myopic foveoschisis. Myopic foveoschisis starts with retinoschisis but ultimately leads to a macular hole via a focal retinal detachment (Ikuno et al. 2008). The natural course of myopic foveoschisis is poor (Gaucher et al. 2007; Shimada et al. 2013), and 11–50 % of patients have a retinal detachment and/or macular hole formation within 2–3 years of follow-up without treatment. The high risk of severe visual loss from macular holes with retinal detachments is a surgical indication.

Myopic foveoschisis occurs mainly in middle-aged to older women. OCT shows various appearances of myopic foveoschisis including lamellar holes and retinal cysts (Benhamou et al. 2002). Myopic foveoschisis begins as retinoschisis without a retinal detachment, i.e., the retinoschisis type. A retinal detachment can start at the fovea after several months or years if there is sufficient traction, i.e., the foveal detachment type (Fig. 22.5) (Ikuno et al. 2008).

Vitrectomy is the most common treatment for myopic foveoschisis (Ishikawa et al. 2001; Kobayashi and Kishi 2003; Ikuno et al. 2004). The surgical goal is release of all retinal traction in order to reattach and reconstruct the normal structure. There are several subtypes; however, the subtypes with the best surgical indications are controversial. We investigated the surgical results and found that eyes with a foveal detachment are good surgical candidates for visual improvement (Ikuno et al. 2008). Other investigators also have reported that a foveal detachment is a positive predictive factor for favorable visual outcomes (Kumagai et al. 2010). However, there is no consensus about the surgical indication, and any type of pathology can be an indication for surgery. The ILM is peeled and injecting a vital dye and gas tamponade are performed frequently to enhance retinal reattachment.

The recovery of visual functional is correlated highly with the OCT findings (Fig. 22.6). We investigated the SD-OCT appearance of 17 eyes with myopic foveoschisis and in relation to visual acuity (VA) (Fujimoto et al. 2013). The mean preoperative central foveal thickness was 470.8 μm. The mean postoperative retinal thicknesses decreased significantly and were 310.4 μm at 1 month, 251.8 μm at 3 months, 218.2 μm at 6 months, and 218.7 μm at 12 months. The preoperative best-corrected VA (BCVA), final integrity of the inner segment/outer segment (IS/OS) junction, and the external limiting membrane (ELM) were associated significantly with the final BCVA. Interestingly, the integrity of the IS/OS and ELM lines were attenuated at 1 month and then started to improve in most cases. This behavior was associated with the mean VA, which decreased temporarily 1 month postoperatively.

We reported that about 50 % of patients with the retinoschisis type of macular hole obtained visual improvement 6 months postoperatively as did 80 % of those with the foveal detachment type and 30 % with the macular hole type (Ikuno et al. 2008). Other investigators reported similar results, i.e., the final vision in the foveal detachment group and non-foveal detachment group improved in 70 % and 42 %, was unchanged in 26 % and 33 %, and worsened in 4 % and 25 % of the eyes, respectively (Kumagai et al. 2010).

Macular hole formation is one of the most severe postoperative complications, with an incidence of about 20 % (Gaucher et al. 2007). To identify the risk factors for secondary full-thickness macular holes after pars plana vitrectomy with ILM peeling, we retrospectively reviewed patients who had undergone those procedures to treat myopic foveoschisis (Gao et al. 2013). A macular hole developed postoperatively in eight (19.0 %) of 42 eyes. No significant association between age, axial length, VA, foveal status, posterior staphylomas, or chorioretinal atrophy was found in patients with and without macular holes. Only the percentage of eyes with an IS/OS junction defect was significantly higher (Fig. 22.7).

The pathogenesis of secondary macular holes after vitrectomy for macular foveoschisis remains unclear. Gass (1995) hypothesized that the Müller cell cone supplies structural support to the fovea and plays a critical role in the pathogenesis of macular holes. Potential trauma to the underlying Müller cells may be a possible explanation for postoperative macular holes. ILM peeling may result in loss of Müller cell end feet in the area from which the ILM was peeled and weakening of the macular glial structure.

Macular holes often lead to retinal detachments in highly myopic eyes. Histologic studies of specimens obtained during vitrectomy have shown that a retinal detachment results from the tangential traction of the vitreous cortex and/or thin ERMs adhering to the retinal surface (Bando et al. 2005; Ishida et al. 2000).

The areas of macular holes with a retinal detachment vary widely. Some patients are stable and the pathology is localized for months within the posterior staphyloma (Fig. 22.8); however, most patients develop an extensive detachment beyond the edge of the staphyloma. A small hole is seen in the central macular area on ophthalmoscopy and can be confirmed by OCT, which generally shows a detached retina and a hole with or without surrounding retinoschisis.

Interestingly, two types of macular holes are seen on OCT in high myopia (Fig. 22.9), and they have distinctly different prognoses (Jo et al. 2012). We investigated 22 eyes that underwent vitrectomy for highly myopic macular holes and the SD-OCT images. Ten eyes had retinoschisis around the macular hole and 12 did not. The patients in the schisis group were significantly older and had a worse VA and higher posterior staphyloma. Preoperative OCT images must be interpreted carefully to determine the surgical results.

Regarding the basic surgical techniques, see Sect. 4.​4. The only difference is the duration of the gas tamponade. A longer period of gas tamponade with perfluoropropane normally is needed to enhance the reattachment (Lim et al. 2014).

The prognosis of macular holes with a retinal detachment is relatively poor. The postoperative VA is an average of 20/200 or less, and retinal reattachment occurs in about 70 % of cases after the initial surgery (Nakanishi et al. 2008). In addition, the macular holes do not close in more than 50 % of cases (Ikuno et al. 2003). Macular buckling, which can be considered when the retina is resistant, converts the vector force on the retinal surface and pushes the retina onto the retinal pigment epithelium (RPE), which is why this procedure normally has a higher success rate of over 90 % compared with vitrectomy (Ripandelli et al. 2001).

The pathogenesis remains controversial; however, the consensus is that local production of vascular endothelial growth factor (VEGF) is somehow upregulated, which leads to CNV growth. The pre-existing lacquer crack is thought to be a risk, and it is found in most cases with myopic CNV (mCNV) (Neelam et al. 2012). A recent OCT study reported that choroidal thinning at the fovea is a risk factor. For instance, our study found that eyes with unilateral mCNV had a significantly thinner choroid under the fovea compared with healthy, myopic, fellow eyes (Ikuno et al. 2010a). The association between choroidal thinning and upregulated VEGF production is not understood fully; however, a circulatory disturbance was reported around the macular area in mCNV (Wakabayashi and Ikuno 2010). Choroidal ischemia is supposed to increase the local VEGF concentration, which leads to VEGF production.

mCNV is normally small and grayish at the macula or adjacent to the crescent of the optic nerve head. This lesion is often pigmented, the so-called Förster-Fuchs spot. The Verteporfin in Photodynamic Therapy (VIP) study (2001) reported that more than 70 % of cases had the classic type, and in 65 % the lesion was subfoveal. Occult CNV and pigment epithelial detachment (PED) are rarely present. mCNV is sometimes accompanied by a small hemorrhage between the photoreceptors and RPE. Fluorescein angiography (FA) is helpful for diagnosis. mCNV appears as hyperfluorescence in the early phase and fluorescein leakage in the late stage. Indocyanine green angiography (ICGA) provides additional information about the RPE and Bruch’s membrane. The location of lacquer cracks also can be more clearly depicted on ICGA images. SD-OCT is also useful for diagnosis, monitoring, and treatment decision-making. mCNV normally grows from the choroid and migrates into the subretinal space. Fibrin reaction and subretinal fluid (SRF) are observed when mCNV is active (Fig. 22.10).