Both high myopia and pachyspectrum diseases such as CSC and polypoidal choroidal vasculopathy are more common in the Asian population [9, 11]. However, pachychoroid diseases are very rare in high myopia. In this study, we describe high myopia which had nontractional foveal detachment with pachychoroid characteristics In this study, no eyes demonstrated intraocular inflammation.
There is a number of complications that require careful scrutiny when dealing with high myopic eyes exhibiting foveal detachment with SRF. Usually, these complications of high myopia include myopic CNV and myopic traction maculopathy. Myopic traction maculopathy is a wide spectrum of related disorders, encompassing vitreomacular traction, myopic foveoschisis and myopic macular hole. In severe forms of myopic traction maculopathy, OCT reveals foveal detachment and foveoschisis with posterior staphyloma in high myopia [12]. In the case of myopic CNV, FA and OCT are recommended for baseline diagnostic examination. In typical myopic CNV, FA reveals well-defined hyperfluorescence in early phases and leakage of fluorescein dye during the late phases, and OCT typically delineates a highly reflective area above the retinal pigment epithelium, namely subretinal hyper-reflective material, with minimal SRF. The relationship between dome-shaped macula and serous foveal detachment in eyes without typical myopic CNV was reported [13]. The morphologic changes in choroidal vascular structure were reported according to presence of posterior staphyloma [14]. However, the main focus of our report was to present serous non-tractional foveal detachment in highly myopic eyes with pachychoroid features and to classify them by presence of type 1 CNV.
Although FA and OCT are the most commonly conducted baseline examinations, in case of clear SRF in highly myopic eyes, these baseline examinations often fail to delineate myopic CNV [4]. ICGA may be more sensitive for detecting CNV or lacquer crack formation [15]. In 7 eyes of the myopic PNV group, the presence of the type1 CNV was confirmed via ICGA or OCTA.
In this study, all the eyes manifested myopic retinal changes consistent with the META-PM criteria [16]. However, all included eyes also showed common characteristics of pachychoroid features. Considering that retinal changes associated with pachychoroid spectrum disease stem from the structural instability inherent with the thick choroid, the naturally low prevalence of pachychoroid features in the thin choroid of high myopia is self-explanatory. In a previous study by Kim et al., choroidal vascular hyperpermeability was not noted in any of the eyes and punctate hyperfluorescent spot was noted in only 4 eyes (4.7%) among 84 eyes with classic myopic CNV [17]. Interestingly, the results in this study indicate that all myopic eyes with thin choroid, with or without type 1 CNV, shared pachychoroid phenotypes. On ICGA, choroidal vascular hyperpermeability, dilated choroidal vessel and punctate hyperfluorescent spot were detected in 13 (92.9%), 14 (100%) and 10 eyes (71.4%), respectively among the 14 eyes enrolled. This is also supported by previous reports claiming that together with dilated choroidal vessels, the punctate hyperfluorescent spot was a co-existing characteristic of choroidal vascular hyperpermeability [18]. On OCT, the presence of pachyvessels beneath SRF was noted in all 15 of 15 eyes (100%) of the current study. These results indicate that nontractional and non-rhegmatogenous serous foveal detachment in high myopia most likely accompany pachychoroid features.
FA and OCT are well-established tests for the diagnosis and monitoring of the activity of myopic CNV because myopic CNV is predominantly classic, type 2 CNV. Meanwhile, the detection of type 1 CNV within flat irregular RPE detachment most often requires on ICGA or OCTA examination. However, polypoidal choroidal vasculopathy and CSC have also been reported in highly myopic eyes [19, 20]. Five of 7 eyes in myopic PNV group had shallow irregular RPE detachment which appears as double layer sign, i.e. flat irregular RPE detachment overlying pachyvessel. The double layer sign indicates the presence of type 1 neovascularization, because CNV vascularity was detected in all of these eyes using ICGA and OCTA. Other 2 of 7 eyes in myopic PNV group showed slight hyper-reflective area with SRF above disrupted retinal pigment epithelium on OCT. Pachyvessels with the dilated choroidal vessel were also observed. This study is the first to address the presence of pachychoroid characteristics as the etiology of myopic serous foveal detachment.
Both ICGA and OCTA are very useful in studying choroidal vascularization especially in high myopia, and high sensitivity and specificity of OCTA are rendered useful in diagnosing myopic CNV [21]. Although the angiographic images in high myopia were difficult to interpret in many cases because of degenerative RPE changes, OCTA, nonetheless, provides high-resolution confocal images of type 1 CNV even in the presence of diffuse RPE window defect. In the current study, the high-flow network located in outer-retinal and choriocapillaris slab shown on OCTA was considered type 1 CNV in high myopia. Our results confirmed that OCTA is very valuable in analyzing outer-retinal neovascular structures for the eyes with serous foveal detachment in high myopia.
The intravitreal anti-VEGF injection is the first-line therapy for myopic CNV [22]. On the other hand, a combination of ranibizumab and PDT was superior to monotherapy for the treatment of non-myopic polypoidal choroidal vasculopathy in improving BCVA and achieving complete polyp regression [23]. In our study, all of 7 eyes in myopic PNV were treated with either intravitreal anti-VEGF injection or PDT, and 3 eyes achieved complete resolution and other 3 eyes, incomplete resolution. The refractory response was noted in one eye.
In myopic CSC group, half-fluence Verteporfin PDT was initially considered except for those with a history of anti-VEGF injection, and if there was an incomplete response, then anti-VEGF injection was performed. After PDT, complete resolution of SRF was noted in two of 3 eyes, while the incomplete response was noted in one eye. Some studies demonstrated PDT as a more favorable method than anti-VEGF injection in the treatment of atypical CSC [24]. In the present study, PDT may be considered as the first optional treatment in myopic CSC. However, further controlled study is required to establish the treatment principles in these groups of patients.
In the case of myopic PNV, our initial treatment was intravitreal anti-VEGF injection. If there was an incomplete resolution of SRF, we tried PDT in the area of choroidal hyperpermeability and SRF. After PDT, complete resolutions of SRF were noted in one of 3 eyes, while incomplete responses were noted in the other 2 eyes. Interestingly, these 2 eyes both had specific structural changes that involved the presence of staphyloma and dome-shaped macula. And incomplete response after PDT in myopic CSC was noted in one eye above that had a dome-shaped macula. According to previous studies, the primary cause of SRF development was not only choroidal vascular permeability, but also mechanical and vascular damage to the choroid by excessive scleral bulging [25]. Various structural changes accompanying high myopia may affect the treatment outcome and make treatment difficult. And these results suggested weaker response in the eyes with myopic PNV to anti-VEGF treatment when compared to anti-VEGF treatment for classic myopic CNV. Despite some time of investigation and clinical experiments since the initial report on PNV, the prognosis and treatment of non-myopic PNV with or without exudation has not been sufficiently addressed. We speculated that PNV is an arterialized mature neovascularization of type 1 CNV over a long period of slow vascular remodeling that increases tolerance and poor response to anti-VEGF treatment.
There were several limitations to the present study. First, the study design was a single-center, retrospective, short-follow up cases that could not represent the prevalence of overall population. Future studies looking at larger and longer series will be needed to characterize these conditions further and determine the optimal treatment approach. Second, the study population was small for both groups. However, this is because the nature of myopia and pachychoroid disease is difficult to coexist. Despite the limitations, this study has significance in that it elicited the interest in the clinical entity of myopic pachychoroid phenotypes as the etiology of myopic serous detachment. We provide new data on angiographic findings on OCTA and present our perspectives in diagnosing and treating myopic CSC and myopic PNV.
In conclusion, Pathologically myopic eyes could have pachychoroid features such as choroidal hyperpermeability or pachyvessel. In this study, we used ‘myopic CSC’ and ‘myopic PNV’ that demonstrate pachychoroid phenotypes. These may result in nontractional serous foveal detachment. In general, these are responsive to anti-VEGF treatment and/or PDT, but shows limited response. Despite of small series, our treatment experience broadens the perspective on disease entity overlapping between high myopia and pachychoroid spectrum disease.