Type 1 neovascularization with polypoidal lesions complicating dome shaped macula

Dome-shaped macula is described as an inward bulge of the macula within a posterior staphyloma in highly myopic eyes. Choroidal neovascularization is a known complication that can cause visual loss in dome-shaped macula. Herein, we describe a patient who presented with features of polypoidal choroidal neovascularization that developed on a background of high myopia with dome-shaped macula.


Background
Dome-shaped macula (DSM) is an inward bulge of the macula within a posterior staphyloma in highly myopic patients [1]. Recently, Imamura et al. [2] utilized enhanced depth optical coherence tomography (EDI-OCT) to demonstrate that the anterior bulge was consequent to relative increases in scleral thickness beneath the macula. Gaucher et al. [1] reported that the prevalence of dome-shaped macula was approximately 10.7% in highly myopic eyes. However, recent reports have utilized multimodal imaging to show that the rate of DSM is higher and in the range between 15 and 20% [3,4].
Choroidal neovascularization (CNV) is a known complication of DSM and occurs at a rate of approximately 20% [4,5]. Deobhakta et al. [6] recently demonstrated that some eyes with DSM will manifest a shallow pigment epithelial detachment (PED) overlying an area of abrupt change in choroidal thickness typically occurring at the edge of the dome. They hypothesized that some of these flat irregular PEDs might harbor type 1 neovascularization. Herein, we describe the multimodal imaging findings in a patient with DSM who presented with type 1 neovascularization with polypidal lesions. To our knowledge, polypoidal type 1 neovascularization has not been documented in the setting of DSM.

Case presentation
A 50-year-old white female with a history of high myopia presented with metamorphopsia and visual deterioration in her left eye that had developed gradually over many months. She had previously been diagnosed with central serous chorioretinopathy and had received photodynamic therapy to the left eye after which two intravitreal injections of bevacizumab were administered (last treatment was over 1 year previously). She was taking metformin for glucose intolerance and was otherwise healthy.
Visual acuities were 20 / 250 in the right eye, improving to 20 / 100 with pinhole and 20 / 800 in the left eye, improving to 20 / 100 with pinhole. Her refractive error was −7.5 and −9.0 diopters right and left, respectively.
The anterior segments were unremarkable and intraocular pressures were 15 mmHg in both eyes. Ophthalmoscopic examination showed peripapillary atrophy and retinal pigment epithelial changes that were consistent with myopic degeneration (Figure 1). There was no hemorrhage.
Horizontal OCT (Heidelberg Spectralis, Heidelberg Engineering, Germany) raster scans did not overtly Open Access  respectively. The vertically oriented OCT line scans showed an abrupt change in choroidal thickness occurring at the inferior edge of the dome (Figure 3). EDI-OCT confirmed an increase in scleral thickness beneath the site of the macular dome.
A complex irregular pigment epithelial detachment was noted at the left macula consistent with a polypoidal lesion and its associated type 1 branching vascular network (BVN) (Figures 2, 3). Shallow subretinal fluid was also seen on these scans. Indocyanine green angiography (TRC-50FX, Topcon Corporation, Tokyo, Japan) and split spectrum amplitude decorrelation angiography (Avanti, Optovue, Fremont, CA, USA) demonstrated the polypoidal lesion and its corresponding feeding vessels (Figure 3). The ICGA also showed relatively larger caliber choroidal vessels in the thicker choroid at the superior edge of the dome.
DSM is associated with high myopia [1] and previous reports have shown that this diagnosis can be missed if the macula is evaluated with a single OCT scan orientation. Liang et al. [4] reported that vertical and horizontal OCT scans are necessary to achieve diagnostic sensitivity for DSM. In their paper, they showed that of those eyes with DSM, the diagnosis could be made using only the vertical section in 77% of cases and using only the horizontal section in 2% of cases. These findings are reflected in our patient in whom the diagnosis of DSM was confirmed only after integration of vertical and horizontal OCT scans to construct a three-dimensional structure.
Vision loss from DSM can be consequent to serous neurosensory detachment masquerading as central serous chorioretinopathy [5]. Foveal retinoschisis [4,7] and choroidal neovascularization [1,7] are other known complications that can arise during the natural course of DSM. The rate of CNV in DSM is approximately 20%, however, little information is available concerning the morphology of these lesions. Utilizing OCT angiography and other imaging modalities, we show that CNV in DSM can manifest a polypoidal configuration. Polypoidal neovascular changes have also been described in central serous chorioretinopathy [8,9], choroidal nevi [10,11], peripheral exudative hemorrhagic chorioretinopathy [12] and optic nerve melanocytoma [13].

Conclusion
Scleral thickness at the site of DSM is increased in contradiction to what is usually found in high myopia [14]. Previous authors used this observation to postulate that control of ocular expansion in myopia may be more complex than initially proposed [2]. Polypoidal changes to type 1 neovascularization in the setting of DSM may reflect the unique stretch and mechanical forces being applied to the macula and choroid in this condition. It will be important to study other cases of CNV in DSM to validate this hypothesis.

Consent
Written informed consent was obtained from the patient for publication of this Case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.