Purpose:
To describe increased choroidal thickness (focal choroidal thickness: FCT, focal choroidal edema: FCE) in patients with neovascular lesions secondary to myopia when assessed by spectral-domain ocular coherence tomography (SD-OCT) under anti-VEGF treatment.
Methods:
Patients with pathologic myopia were retrospectively screened by the evaluation of SD-OCT images made with the TruTrack™ (eyetracking) technique to enable longitudinal follow-up at the same fundus locations between 07/2009 and 09/2011. The contours of the choroid, signs of retinal degeneration and sub-/intra-retinal fluid were evaluated in a masked fashion. To avoid inaccuracies of the absolute values (due to axial elongation) relative FCT values were calculated as a quotient of FCT (maximum choroidal thickness in the case of obvious FCE at baseline) related to FCT at follow up, measured at the same location of the corresponding sections.
Results:
11 of 90 patients (12 eyes) with pathologic myopia showed clear signs of FCE, 6 of them without evidence of any directly overlaying choroidal neovascularization (CNV), arising from scars and RPE lines bent upwards. The curvatures of the pigment epithelium as well as the normalization of the choroid (related to the adjacent tissue) in response to the anti-VEGF treatment suggest an exudative origin of the fluid, confirmed by leakage in fluorescein angiograms in 3 patients. The morphologic changes in these patients before and after treatment with bevacizumab did not support the presence of fibrovascular tissue or advanced endothelial tube formation. There were no special demographic characteristics of the patients (3 male, 8 females; age range: 22-60 years). In all 12 eyes, the choroidal edemas were accompanied by mild intraretinal fluid, wheras the initial FCT was originally increased to a factor of 1,86 (± 0,43) compared to the choroidal space after the treatment (no FCE within 2.4 months).
Conclusions:
FCE might be an early characteristic of neovascular activity in pathologic myopia, previously not described in the literature. While many studies focused on the choroidal thinning and atrophy, a circumscribed thickening of the choroid may also take place in some patients as first response to VEGF production. At follow up, the absence of fibrosis in 6 eyes and no increase in fibrosis in the other 6 eyes count in favor of a predominant exudative phenomenon, although further angiographic examinations and evaluation of larger cohorts still have to clarify the impact and origin of the potential leakage. So far, FCE seems to be both, an activity sign of CNV and phenomenon prior to CNV formation secondary to pathologic myopia.
Keywords: choroid • myopia • choroid: neovascularization