Florian Alten

Exploring choriocapillaris under reticular pseudodrusen using OCT-Angiography

PurposeTo evaluate if choriocapillaris (CC) vessel density and CC decorrelation signal index are compromised in eyes with reticular pseudodrusen (RPD) using optical coherence tomography angiography (OCT-A).MethodsDecorrelation values in OCT-A CC images of 20 RPD patients were measured in the outer superior and the outer inferior sector of the EDTRS grid and compared to age-matched healthy controls. CC vessel density and CC decorrelation signal index were measured within a 30 μm and a 10 μm OCT-A CC slab. CC data were correlated to number of RPD lesions, predominantly present RPD stage, predominantly present RPD type, retinal area affected by RPD and choroidal thickness (CT).ResultsCC vessel density and CC decorrelation signal index decreased in correlation to advancing age in healthy subjects particularly in subjects older than 60 years (CC vessel density: 30 μm: p=0.0019; 10 μm: p=0.0014; CC decorrelation signal index: 30 μm: p=0.0005; 10 μm: p=0.0003). In the RPD group, CC vessel density (outer superior sector, 10 μm: 98.299) and CC decorrelation signal index (89.07) were significantly reduced compared to controls (99.203, p=0.0002; 98.09, p=0.0010). The number of RPD lesions was correlated to a reduced CC vessel density (30 μm: p=0.0355) but not to changes in CC decorrelation signal index. No correlations were found between CC parameters and either RPD stage, RPD type, size of RPD affected area or CT.ConclusionsOCT-A reveals a distinct reduction in CC vessel density and CC decorrelation signal index in eyes affected by RPD, which emphasizes the relevance of the CC layer in RPD pathogenesis.

Prediction of retinal pigment epithelial tear in serous vascularized pigment epithelium detachment.

Purpose:  The aim of the study was to identify predictive factors for detection of impending retinal pigment epithelium (RPE) tears in patients under anti‐VEGF therapy for treatment of retinal pigment epithelial detachment (PED) due to exudative age‐related macular degeneration (AMD) using near‐infrared reflectance imaging (NIR), spectral‐domain optical coherence tomography (SD‐OCT) and fluorescein angiography (FLA).

Temporal retinal nerve fibre layer thinning in cluster headache patients detected by optical coherence tomography

Background The exact pathophysiology of cluster headache (CH) is still not fully clarified. Various studies confirmed changes in ocular blood flow during CH attacks. Furthermore, vasoconstricting medication influences blood supply to the eye. We investigated the retina of CH patients for structural retinal alterations with optical coherence tomography (OCT), and how these changes correlate to headache characteristics, oxygen use and impaired visual function. Methods Spectral domain OCT of 107 CH patients – 67 episodic, 35 chronic, five former chronic sufferers – were compared to OCT from 65 healthy individuals. Visual function tests with Sloan charts and a substantial ophthalmologic examination were engaged. Results Reduction of temporal and temporal-inferior retinal nerve fibre layer (RNFL) thickness was found in both eyes for CH patients with a predominant thinning on the headache side in the temporal-inferior area. Chronic CH patients revealed thinning of the macula compared to episodic suffers and healthy individuals. Bilateral thinning of temporal RNFL was also found in users of 100% oxygen compared to non-users and healthy controls. Visual function did not differ between patients and controls. Discussion Our OCT findings show a systemic effect causing temporal retinal thinning in both eyes of CH patients possibly due to attack-inherent or medication-induced frequent bilateral vessel diameter changes. The temporal retina with its thinly myelinated parvo-cellular axons and its more susceptible vessels for the vasoconstricting influence of oxygen inhalation seems to be predisposed for tissue damage-causing processes related to CH.

Vessel Labeling in Combined Confocal Scanning Laser Ophthalmoscopy and Optical Coherence Tomography Images: Criteria for Blood Vessel Discrimination

Introduction The diagnostic potential of optical coherence tomography (OCT) in neurological diseases is intensively discussed. Besides the sectional view of the retina, modern OCT scanners produce a simultaneous top-view confocal scanning laser ophthalmoscopy (cSLO) image including the option to evaluate retinal vessels. A correct discrimination between arteries and veins (labeling) is vital for detecting vascular differences between healthy subjects and patients. Up to now, criteria for labeling (cSLO) images generated by OCT scanners do not exist. Objective This study reviewed labeling criteria originally developed for color fundus photography (CFP) images. Methods The criteria were modified to reflect the cSLO technique, followed by development of a protocol for labeling blood vessels. These criteria were based on main aspects such as central light reflex, brightness, and vessel thickness, as well as on some additional criteria such as vascular crossing patterns and the context of the vessel tree. Results and Conclusion They demonstrated excellent inter-rater agreement and validity, which seems to indicate that labeling of images might no longer require more than one rater. This algorithm extends the diagnostic possibilities offered by OCT investigations.

Multimodal Retinal Vessel Analysis in CADASIL Patients

Purpose To further elucidate retinal findings and retinal vessel changes in Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) patients by means of high resolution retinal imaging. Methods 28 eyes of fourteen CADASIL patients and an equal number of control subjects underwent confocal scanning laser ophthalmoscopy (cSLO), spectral-domain optical coherence tomography (SD-OCT), retinal nerve fibre layer (RNFL) measurements, fluorescein and indocyanine angiography. Three vessel measurement techniques were applied: RNFL thickness, a semiautomatic software tool based on cSLO images and manual vessel outlining based on SD-OCT. Results Mean age of patients was 56.2±11.6 years. Arteriovenous nicking was present in 22 (78.6%) eyes and venous dilation in 24 (85.7%) eyes. Retinal volume and choroidal volume were 8.77±0.46 mm3 and 8.83±2.24 mm3. RNFL measurements showed a global increase of 105.2 µm (Control group: 98.4 µm; p = 0.015). Based on semi-automatic cSLO measurements, maximum diameters of arteries and veins were 102.5 µm (106.0 µm; p = 0.21) and 128.6 µm (124.4 µm; p = 0.27) respectively. Manual SD-OCT measurements revealed significantly increased mean arterial 138.7 µm (125.4 µm; p<0.001) and venous 160.0 µm (146.9; p = 0.003) outer diameters as well as mean arterial 27.4 µm (19.2 µm; p<0.001) and venous 18.3 µm (15.7 µm; p<0.001) wall thicknesses in CADASIL patients. Conclusions The findings reflect current knowledge on pathophysiologic changes in vessel morphology in CADASIL patients. SD-OCT may serve as a complementary tool to diagnose and follow-up patients suffering from cerebral small-vessel diseases.

Reading the signs: Microrips as a prognostic sign for impending RPE tear development

described by Salvatore et al. (2011) as increased reflectivity and thickness in the area of the MRNF which is accompanied by a posterior cone of shadowing due to increased nerve fibre layer thickness. Our findings were similar, and additionally we have also investigated Type III lesions and found less prominent features of MRNFs in SD-OCT images (Fig. 1). This might be important because it may lead to difficulties in differential diagnosis with similar lesions (cotton wool spots, etc.) In previous studies, MRNFs have been most commonly located in the superior peripapillary region (Straatsma et al. 1981). Our study showed that the most common type was Type I (present in one temporal arcade), of which the superotemporal quadrantwas the most affected retinal area consistent with that study. However, the Beijing eye study found that MRNFs are located most often in the temporal inferior fundus region (You et al. 2007). In conclusion, our findings showed that the MRNF prevalence was similar in other populations, but bilateral involvement was higher. OCT findings, which were very prominent in Type 1 and Type II MRNFs, may be confusing with other pathologies in Type III lesions.

Response of vascular pigment epithelium detachment due to age-related macular degeneration to monthly treatment with ranibizumab: the prospective, multicentre RECOVER study

To assess the effects of monthly intravitreal ranibizumab injections in patients with vascularized pigment epithelium detachment (vPED) secondary to age‐related macular degeneration (AMD).

OCT-angiography for assessing risk of retinal pigment epithelium tear in patients with vascular retinal pigment epithelium detachment due to AMD

NF1, and the choriocapillaris has been shown to be thinner and compressed above choroidal nodules (Rao & Choudhry 2014; Abdolrahimzadeh et al. 2015, 2016). Choroidal thinning in NF1 may be due to the presence of choroidal nodules which compromise choroidal blood flow (Abdolrahimzadeh et al. 2015). The choroid is a multifunctional structure with a dynamic vascular nature, and it can be hypothesized that the presence of choroidal nodules and generalized choroidal thinning in NF1, which is an agerelated chronic disease, may induce compensatory mechanisms of the choroid in order to provide nutrients and oxygen to the overlying retina similar to the mechanism hypothesized in extreme choroidal thinning in myopia. However, our results should be interpreted with caution as the number of cases reported is small and the abnormal vessels could not necessarily be specific to NF1 as these could possibly be found in other diseases and a larger population of healthy subjects.

OCT Angiography reveals changes in foveal vessel architecture and foveal flow in central serous chorioretinopathy

Editor, C entral serous chorioretinopathy (CSC) represents one of the most common vision-threatening retinopathies after age-related macular degeneration, diabetic retinopathy and retinal vein occlusion. It is characterized by an accumulation of subretinal fluid (SRF) sometimes in association with a retinal pigment epithelium (RPE) detachment. The exact pathophysiological mechanism is still a matter of debate. Nevertheless, based on multimodal imaging numerous authors have postulated that a hyperpermeable choroid and a dysfunctional RPE cause the accumulation of SRF (Daruich et al. 2015). So far, the information on secondary effects on retinal vessels in this disease is limited. With the advent of optical coherence tomography angiography (OCT-A), a novel non-invasive depthselective imaging tool, an enhanced visualization of retinal blood flow and the foveal avascular zone (FAZ) has become available. We included 16 CSC patients that showed characteristic chorioretinal alterations in the affected eye and no morphological or functional change in the fellow eye based on spectral domain OCT and fluorescence angiography (FA). Optical coherence tomography angiography imaging was conducted with a commercial OCTsystem (AngioVue, RTVue XR Avanti SD-OCT; Optovue, Fremont, CA, USA ). The device obtains volumetric scans of 304 9 304 A-scans at 70 000 A-scans per second using a light source centred on 840 nm. The software offers automated segmentation of retinal layers as well as a quantification of flow density in the superficial layers of the retina defined as flow per volume in percent (AngioAnalytics, Optovue). In both the affected eye and the nonaffected fellow eye of CSC patients, the flow density in the foveal (FDfov) region of a foveally-centred Early Treatment Diabetic Retinopathy Study grid was measured and compared to data of age-matched healthy control eyes. Besides, the FAZ was determined in both eyes of CSC patients using a manual measurement tool of the software (Fig. 1).

OCT-Angiography strengthens the theory of a purely serous pigment epithelium detachment in age-related macular degeneration.

Dear Editor, Serous pigment epithelium detachments (PED) are characterised by a collection of fluid in the subpigment epithelial space between the retinal pigment epithelium (RPE) and Bruch’s membrane (BM) and appear as sharply demarcated elevations of the RPE. Most frequently, they are seen in age-related macular degeneration (AMD). Although there are decades of longitudinal experience with serous PED due to AMD, the exact underlying pathomechanism is still a matter of debate. Bird and Marshall introduced the hypothesis that age-related deposition of lipids in BM may change its permeability, consequently altering retinochoroidal flow [1]. Therefore, accumulated fluid in the sub-RPE space is unable to pass through BM resulting in an RPE elevation. The RPE physiologically pumps fluid in the subRPE space, which leads to a continuous increase in PED height. However, other authors deny the existence of a purely serous PED in AMD and postulate that subRPE fluid originates from a neovascular component. We propose to use optical coherence tomography angiography (OCT-A) to discuss this yet unsolved pathophysiologic issue from a new perspective. Figure 1 shows retinal imaging of two exemplary treatment-naïve patients with serous PED lesions due to AMD. Fluorescein angiography (FA) reveals an early hypofluorescence followed by a progressive and homogeneous pooling of the PED cavit ies (Fig. 1a, b, e, f). Late pooling of serous PEDs is typical and may make it difficult to differentiate these PEDs from vascularised ones based on FA alone. Oftentimes, indocyanine green angiography (ICGA) distinguishes serous from vascularised PEDs showing the presence of a hyperfluorescent membrane within the PED indicating an underlying choroidal neovascularization (CNV) [2, 3]. In our patients, ICGA shows a hypofluorescence in both the early and the late phases with blockage of the normal choroidal vasculature (Fig. 1c, g). Notably, there is no evidence of any flow signal in both PED lesions in OCT-A (Fig. 1d, h), which strengthens the theory of a purely serous PED without any underlying or adjacent CNV. Current OCT-A imaging technology is not without limitations. In general, OCT-A is a nascent technology and currently under evaluation. Particularly, OCT-A imaging under the RPE is a relatively unexplored area. It does not visualise very slow blood flow and may produce artifacts, particularly, projection artifacts of retinal vessels when an imaging slab is selected at the level where the choriocapillaris is anatomically expected to be or at steep edges of large PED lesions [4]. Furthermore, future software algorithms may reveal structures that are currently not being visualized. OCTA slab thickness should be large enough to ensure that a small membrane cannot be missed. For OCT-A imaging in these patients, the outer retina slab was chosen from the automatic software settings of the OCT-A * F. Alten florian_alten@yahoo.de