Pascal W. Hasler

Correlation between intraretinal changes in diabetic macular oedema seen in fluorescein angiography and optical coherence tomography

Purpose:  To study the relationship between intraretinal optical coherence tomography (OCT) and fluorescein angiography (FA) findings in eyes with diabetic macular oedema (DMO).

Local retinal sensitivity in relation to specific retinopathy lesions in diabetic macular oedema

Purpose:  To study microperimetric macular sensitivity in diabetic macular oedema (DMO) in relation to lesion characteristics obtained by optical coherence tomography (OCT), colour fundus photography, and fluorescein angiography (FA).

Safety study of 38 503 intravitreal ranibizumab injections performed mainly by physicians in training and nurses in a hospital setting

To evaluate and to compare the safety of intravitreal ranibizumab injections performed by physicians and nurses at a single large hospital clinic in Denmark during 5 years.

Enhanced resolution and speckle‐free three‐dimensional printing of macular optical coherence tomography angiography

V olume rendering of optical coherence tomography angiography (OCTA) is a rapidly evolving imaging tool, which has been shown to preserve the three-dimensional (3D) architecture of various retinal diseases including diabetic retinopathy, retinal vein occlusion and macular telangiectasia type 2 (Spaide 2015). This form of imaging avoids flattening of subvolumes of tissue as is done in en face imaging and does not require the use of segmentation, which often is incorrect in retinal disease. Volume rendering can illustrate the close relationship between the flow signal and structural optical coherence tomography (OCT) information from which it is derived. By extending the OCT volume rendering technology into stereolithography, the whole 3D experience can be made physically tangible by producing life-like models as well as surgical templates and implants on a larger scale for an additional conceptualization and tactile feedback. The introduction of stereolithography in medicine has already been demonstrated to be a useful tool for surgical planning in congenital heart surgery, reconstructive surgery and in simulation training for aneurysmal surgery. Such 3D models might also be important in ophthalmology for surgical training or planning of microsurgical procedures and for teaching purposes for students and patients (Choi et al. 2016). In this report, we demonstrate the first stereolithographic retinal vessel models based on standard OCTA. Two methods were developed to obtain a printable 3D model (Fig. 1). Nine repeats of tracked OCTA measurements (3 mm 9 3 mm scan area, 245 9 245 pixel), were performed on one healthy right macula of a 35-yearold emmetropic femalewithZeissCirrus HD-OCT Model 5000 with ANGIOPLEX (Review software 9.0.0.281; Carl Zeiss Meditec, Jena, Germany). The nine OCTA volumes were aligned and averaged into one final “enhanced resolution” OCTA volume (“erOCTA”), and a print model was saved in obj format. Another method for the 3D printing used single volume rendering and was tested first and freed from speckle noise using a recently developed 3D speckle denoiser. The 3D data stack was imported in open source IMAGEJ (v1.467; ref – Rasband, W.S., IMAGEJ, US National Institutes of Health, Bethesda, MD, USA, https://imagej.nih.gov/ij/, 1997–2016) and after thresholding, exported in obj format. This 3D mesh was modified with a view to seal vessel gaps and remove digital artefactswith the digital sculpting tool zBrush 4R7 (Pixologic inc., Los Angeles, CA, USA). A printable prototype was transferred to the 3D printing service company i.materialise (Materialise HQ, Leuven, Belgium) and printed in transparent resin constructed from a hardened liquid. The material is strong, hard, stiff and water-resistant and is suited for models that require a smooth, good-quality surface with a transparent look. Design specifications for 3D printing included minimum wall thickness of 1 mm, minimum details of 0.5 mm, accuracy 0.2% and a size of 200 9 200 9 15 mm, although 3D prints 300 9 300 9 28 mm have been made (Fig. 2). This corresponds to a magnification of 66.7–100 times. Finally, to accentuate the details of the retinal vessels, one stereolithographic replica was charged by conduction by submerging it in a silver bath and copper bath for 48 hr and subsequently in a gold bath, 24 karat. The 3D print depicts the typical arrangement of the superficial vascular complex vessels that lie in a linear pattern along the inner retinal surface with vertical branches into deeper retinal vascular networks. Video S1 demonstrates a 3D print of a normal 3DOCTA, especially the foveolar avascular zone (FAZ). These vessels do not necessarily look round but are thickened in the Z-axis because of decorrelation tails. The 3D rendering showed partially irregular thickening of the vessels. In addition, multiple, small, wart-like protrusions were found on the vessel surface, which appeared to be localized above and perpendicular to the vessel direction and in direction of

Delayed response of the retina after hyperbaric oxygen exposure.

Purpose:  To examine retinal electrophysiological function and retinal thickness in healthy eyes before and after hyperbaric oxygen (HBO) exposure.

Targeting neuronal and glial cell types with synthetic promoter AAVs in mice, non-human primates, and humans

Targeting genes to specific neuronal or glial cell types is valuable both for understanding and for repairing brain circuits. Adeno-associated viral vectors (AAVs) are frequently used for gene delivery, but targeting expression to specific cell types is a challenge. We created a library of 230 AAVs, each with a different synthetic promoter designed using four independent strategies. We show that ~11% of these AAVs specifically target expression to neuronal and glial cell types in the mouse retina, mouse brain, non-human primate retina in vivo, and in the human retina in vitro. We demonstrate applications for recording, stimulation, and molecular characterization, as well as the intersectional and combinatorial labeling of cell types. These resources and approaches allow economic, fast, and efficient cell-type targeting in a variety of species, both for fundamental science and for gene therapy.

The grey fovea sign of macular oedema or subfoveal fluid on non-stereoscopic fundus photographs.

To describe the grey fovea sign of fovea‐involving macular oedema or subretinal fluid accumulation in red‐free fundus photography.

3D printing of the choroidal vessels and tumours based on optical coherence tomography

T he choroid has the highest blood flow of any structure in the human body with specific hemodynamic regulatory mechanisms that differ from those of the retinal circulation. It is modulated by a strong autonomic input and is largely insensitive to light stimulation and to differences in blood oxygenation (Kur et al. 2012). Detailed imaging of the choroidal layers has recently been facilitated by the introduction of new imaging modalities such as enhanced depth imaging optical coherence tomography (EDI-OCT) and swept source OCT (SSOCT) (Mrejen & Spaide 2013). One of the more important limitations of routine OCT lies with the two-dimensional (2D) display of static images on a computer screen, hampering characterization of clinically important structural features, such as depth and spatio-anatomical localization. This drawback has been circumvented by the advent of threedimensional (3D) imaging techniques that provide detailed and problemoriented information on both the retinal and choroidal compositions, including volume rendering (Spaide 2015). Similar to routine OCT, this technique is restricted to 2D display in computer screens. Recently, a new method has been reported in which printing of OCT data has been described in a patient with an epiretinal membrane (Choi et al. 2016). This study describes for the first time the use of a 3D printing technique, speckle-free 3D choroidal angiography and tumoropsy (Maloca et al., 2016), applied to3Dprintingof choroidalvessels and pigmented choroidal tumours. In this study, retrospective 1050 nm OCT volumes were collected from healthy eyes and eyes with pigmented choroidal tumours to evaluate choroidal vessel architecture and tumour 3D printing. Inclusion criteria were age >18 years, adequate media clarity for fundus imaging, good central fixation and visual acuity >20/20. Exclusion criteria were nystagmus, poor cooperation and dry eye syndrome. All subjects underwent a comprehensive baseline ophthalmologic examination to exclude any potential retinal or choroidal disorders. Written informed consent was obtained from all patients, and approval was attained from the local ethical committee in accordance with the Declaration of Helsinki and in compliance with data protection regulations. All retinal OCT volumes were acquired in nondilated pupils with a SSOCT device (DRI OCT Triton; Topcon, Tokyo, Japan). The SSOCT volume was captured in a 3D scan pattern over a 3 9 3 mm, 6.0 9 6.0 mm or 9 9 12 mm area, respectively, centred on the region of interest (ROI) with 256 B-scans and a scan density of 512 9 256 pixel. Image processing was performed with a previously published 3D speckle-noise removal method with structure preservation (Gyger Cyrill et al. 2014). For choroidal vessel lumen and tumour extraction, the hyporeflective choroidal vessels and hyperreflective tumour structures, respectively, were manually segmented by threshold filtering in the speckle-free OCT volume (IMAGEJ v1.467; ref – Rasband, W.S., IMAGEJ, US National Institutes of Health, Bethesda, MD, USA, https:// imagej.nih.gov/ij/, 1997–2016) by extracting lumen information from the scan volume. The 3D information of the processed choroid was saved as obj-file which was then enhanced by sealing gaps in the mesh or removing obvious artefacts. Ultimately, a 3D printable OCT model was obtained (Fig. 1). Some models were sent for 3D stereolithography printing in transparent resin or constructed from a hardened liquid (i.materialise, i.Materialise HQ, Leuven, Belgium). One model was submerged in a bath of carat gold (24K) to increase robustness and durability. Other models were printed in additive fused deposition modelling using a gypsum powder for testing combined vessel and tumour structure printing, respectively (3d-prototyp.com, Stans, Switzerland). Design specifications for 3D printing included minimum wall thickness of 1 mm, minimum details of 0.5–1 mm and a size of 130 9 200 9 10 mm. In addition, 3D prints of 300 9 300 9 23 and 210 9 390 9 23 mm have been made (Fig. 2). This corresponds to a magnification of up to 70–100 times. Analysis of 3D print models allows a detailed spatio-anatomical characterization of choroidal vessels and their