The new technique of optical coherence tomography (OCT) angiography allows a non-invasive reconstruction of the three-dimensional structure of the total retinal and choroidal vascularization within seconds. There are still limitations caused by movement artefacts, superimposition of superficial retinal vessels at the retinal pigment epithelium (RPE) level and insufficient three-dimensional imaging modalities. Initial experiences with this new method and especially the correlation with the current standard diagnostic procedure of fluorescein angiography show that new information can be obtained regarding specific vascular and neovascular changes. For three-dimensional neovascular changes, such as those found in exudative age-related macular degeneration (AMD,) a more sophisticated diagnostic analysis strategy must be specifically developed. Initial experiences demonstrate that the differentiation into the various types of choroidal neovascularization (CNV) by fluorescein angiography, specifically for type 1 (occult) and type 2 (classical) can also be visualized by OCT angiography. Furthermore, the new technology provides additional information on the choroidal and outer retinal changes associated with this disease, which may result in a better understanding of the underlying pathology.

This article reports the case of a 72-year-old woman with pigment epithelial detachment with occult choroidal neovascularization (CNV) in exudative age-related macular degeneration (AMD) which developed under anti-vascular endothelial growth factor (VEGF) therapy of a tear in the retinal pigment epithelium (RPE). In the area of free RPE autofluorescence was completely absent and the microperimetry in this area showed an absolute scotoma. The visual acuity was 0.1. After continuation of anti-VEGF therapy because of persistent subretinal and intraretinal fluid over 3 years an increased autofluorescence was observed and the microperimetry showed an increase in central retinal sensitivity. The central visual acuity improved to 0.5 and in this area a whitish subretinal tissue formed morphologically. In the spectral domain optical coherence tomography (SD-OCT) image this structure was hyperreflective which might suggest a certain regeneration process of the RPE under anti-VEGF-therapy.

The aim of the following extended case study was to analyse whether choroidal neovascularisation (CNV) in vascularised epithelial detachments (PED) in OCT angiography (OCT-A) can be better visualised in OCT-A than in the established angiographic methods during the course of anti-VEGF therapy and if possible used to quantify the CNV size and flow area. These findings were compared with other SD-OCT characteristics of the lesion (PED height, retinal thickness). 8 patients with PED and associated CNV were diagnosed with multimodal imaging and additionally OCT angiography was performed. The CNV region in the B-scan of the OCT-A was detected with a fine segmentation setting (20 µm) parallel and just below the retinal pigment epithelium (RPE). The CNV area was manually marked, and the size of the CNV and the vessel section (flow area) were analysed with the evaluation tool of the device. This measurement was performed both initially and after anti-VEGF therapy (3 injections). At the same time, the visual acuity (logMAR) and the SD-OCT parameters of PED height and retinal thickness were determined before and after therapy and also statistically compared. Initially, the size of CNV in OCT-A showed a large phenotypic range of variation (0.33 - 1.35 mm, mean 0.71 mm). This decreased significantly under therapy (after therapy 0.44 - 0.84 mm, mean 0.57 mm, p = 0.02). The proportion of the vessels analysed within the CNV (flow area) varied as well (0.21 - 0.88 mm, mean 0.45) and decreased under therapy (0.08 - 0.44 mm after therapy), mean 0.27 mm, p = 0.07). The height of PED in SD-OCT was initially different (initially 274 - 1459 µm, mean 607 µm), but showed only small changes (132 - 1317 µm, mean 524 µm, p = 0.09) under therapy. This also applied to the mean retinal thickness (before therapy 315 µm, after therapy 294 µm, p = 0.5). Mean visual acuity also improved only slightly (p = 0.7) after therapy. from initially 0.51 to 0.45 logMAR. The combination of SD-OCT and OCT-A offers significantly improved visualisation and quantification of CNV in a vascularised PED. With the help of OCT-A imaging, changes in the perfusion/size of the CNV can be quantified. Together with the retinal activity signs, this allows a second activity assessment of the CNV under anti-VEGF therapy. Due to its three-dimensional structure, especially for this subtype of the exudative AMD, it is of the utmost importance to develop three-dimensional imaging for both structural SD-OCT and the OCT-A.

In patients with recurrent or high SD-OCT-based activity of exudative AMD lesions, a switch of the treatment strategy from ranibizumab to aflibercept can achieve a new functional stability in spite of multiple pretreatment. We found morphological indications of a regression of intraretinal edema and improvement in the photoreceptor area. In the context of a well-defined treatment strategy, a switch from anti-VEGF therapy to a similar active substance is safe. Before a definitive evaluation can be made, prospective controlled conditions are required to verify the clinical benefits of the switch.

Recent developements in OCT technology using high speed acquisition and calculation of consecutive scans (SSADA = split spectrum amplitude decorrelation algorithm) have resulted in the possibility to demonstrate retinal and choroidal vessels in the macula. This new technology of "OCT angiography" thus allows the non-invasive and rapid (within seconds) reconstruction of the three-dimensional structure of the retinal and choroidal vascularisation. There are still limitations caused by movement artefacts, superposition of superficial retinal vessels at the RPE level or insufficient three-dimensional imaging, but the first experience with this new method and especially the correlations with the current standard diagnostic procedure fluorescein angiography shows that especially for vascular changes which are predominantly in one retinal layer (e.g., the inner retina) like in diabetic retinopathy or retinal vein occlusions, a very good correlation can be seen. Also in MacTel type 2 patients the proposed vascular changes in the deeper capillary network of the retina can be visualised very well with OCT angiography. In contrast, more three-dimensional vascular changes like the neovascular complex in exsudative AMD need a more sophisticated diagnostic analysis strategy, which has still to be developed. However, the first experience also demonstrates that fluorescein angiographic differentiation can also be seen in OCT angiography. In addition, the new technology gives additional information about the choroidal and outer retinal changes in these pathologies, which may result in a better understanding of the underlying pathologies.