Gabriel Coscas

‘False-friend’ images on optical coherence tomography angiography: early choroidal neovascularization or artefact?

O ptical coherence tomography (OCT) angiography is a novel imaging technology that enables clear in vivo visualization of perfused blood vessels without having to use injectable dyes. It provides high-resolution 3D images of the retinal and choroidal microvasculature by separating static (tissue) from motion (blood flow) signals. (Jia et al. 2014; Coscas et al. 2015; de Carlo et al. 2015). Nevertheless, there are still several doubtful findings that are mainly related to the thickness of C-scan sections, segmentation errors, ‘ghost images’ due to retinal pigment epithelium (RPE) reflection and the prototype nature of many optical coherence tomography angiography (OCT-A) devices. In this retrospective case series, each patient was evaluated using a Spectralis OCT-A prototype (Heidelberg Engineering, Heidelberg, Germany) with a 15 9 5° volume scan (131 B-scans). Optical coherence tomography (OCT) angiograms were analysed with multiple 30-lm-thick slabs, manually fine-tuned from the nerve fibre layer to the choroidal– scleral interface. On OCT-A, choroidal neovascularization (CNV) was defined by evidence of a hyperintense decorrelation signal, both in Band C-scan angiograms, immediately above the retinal pigment epithelium (RPE) (CNV type II) and/ or below the RPE (CNV type I) between the Bruch’s membrane and the RPE layers.

Optical Coherence Tomography Findings in the Choroid

We discuss the role of optical coherence tomography (OCT) in the evaluation of the changes in the choroid from normal to different diseases, according to age and refractive status. Advances in spectral domain (SD)-OCT have enabled clinicians to visualize in detail the various structures of the choroid using the enhanced depth imaging technique, and, more recently, with the new generation of prototypes swept source (SS)-OCT (1,050 nm and higher scan rate). The software update version (5.4) automatically produced inverted capturing images and the eye tracking technology improves image quality, with a high inter- and intraobserver reproducibility but without automatic measuring software. Choroidal thickness (CT) is defined as the distance between the outer borders of the RPE to the hyper-reflective line of the choroid/sclera boundary at predefined intervals of the inner surface of the sclera. The boundaries of the choroid are difficult to define: not so much for the anterior limit (posterior limit of RPE band), but mainly because of the posterior limit that varies in appearance. Normal choroidal thickness has been described with the Spectralis® as 287 ± 76 µm and with the Cirrus® as 272 ± 81 µm, with a statistically significant reproducibility (Bland and Altman). CT is thickest subfoveally and thins nasally more than temporally. There is a negative correlation between CT and age (decrease of 1.56 per year). Subfoveal CT in subjects aged more than 70 years is 224.8 ± 52.9 µm. These results are statistically different from CT in wet age-related macular disease (171.2 ± 38.5 µm) and from CT in dry early age-related macular disease (177.4 ± 49.7 µm), as well as from CT in vascular polypoidal choroidopathy (438.3 ± 87.8 µm) and CT in central serous choroidopathy (367.81 ± 105.56 μm).

‘En Face' Optical Coherence Tomography with Enhanced Depth Imaging of Different Patterns of the Choroidal Neovascular Network in Age-Related Macular Degeneration

The purpose of this study was to develop a method of segmentation using ‘en face spectral domain-optical coherence tomography (SD-OCT) (‘en face C-scans) to evaluate different patterns of the choroidal neovascular network (CNV) due to age-related macular degeneration (AMD). Materials and Method: A series of 90 patients with AMD comprising 30 cases of subfoveal fibrovascular pigment epithelial detachment, 15 cases of classic CNV and 35 cases of polypoidal choroidal vasculopathy. Fluorescein angiography, indocyanine green angiography and OCT (Spectralis, Heidelberg, Germany) images were analyzed. Volume acquisition of 97 enhanced depth imaging sections at 30-µm intervals was obtained, with a sum of 9 images for each retrofoveal scan. The image was superimposed on infrared and SLO ICG images to confirm the neovascularization. Results: Conventional SD-OCT only provides anteroposterior planes that only visualize the exudative reaction of the neovascular network. This new ‘en face SD-OCT technology allows analysis of not only the contours and the shape of the detachment but also, and most importantly, visualizes the choroidal neovascular network in different patterns due to AMD. This imaging is obtained by means of an ‘en face frontal mode with dynamic analysis in video or on frozen images, section by section, compared to standard SD-OCT or ICGA images with point-by-point correspondence. Conclusion: Until now, the CNV itself was not precisely detectable on conventional SD-OCT but only suggested by an exudative reaction. This new ‘en face SD-OCT technology with dynamic segmentation of the macula allows to visualize the contours and the shape of the fibrovascular pigment epithelial detachment as well as the CNV in fibrovascular pigment epithelial detachment. SD-OCT can demonstrate direct signs of CNV within a pigment epithelial detachment and their localization, seen for the first time on OCT, without injection of dye in patients with a stable fixation point ‘en face and will bring help for the easy detection of CNV and the decision for retreatment easier. ‘En face OCT of classic CNV in AMD also allows to determine the origin of the CNV at the level of the choriocapillaris, the precise location of the ‘effraction of the retinal pigment epithelium layer, the hyper-reflective course of type 2 CNV, in front of the retinal pigment epithelium and the correspondence between the CNV and the ‘intraretinal dense zones, and between ‘en face OCT images and angiograms. ‘En face OCT imaging of polypoidal choroidal vasculopathy allows analysis of the contours and number of polyps, visualization and localization of the abnormal choroidal network and their localization inside the (thickened) choroid, choriocapillaris and Bruchs membrane without the injection of a dye.

Swept Source Optical Coherence Tomography versus Enhanced Depth Imaging-Spectral Domain Optical Coherence Tomography in Age-Related Macular Degeneration

The introduction of spectral domain-optical coherence tomography (OCT) with combined enhanced depth imaging constitutes major technological progress. Enhanced depth imaging spectral domain-OCT provides a comprehensive and continually evolving range of imaging tools for the macula, optic disc, and anterior segment of the eye. The arrival of the swept source-OCT imaging system in 2013 represents eagerly awaited new technology. Swept source-OCT provides a large examination field, allows deeper penetration through use of an infrared wavelength of 1,050 µm, and provides a reduced masking effect on the pigment epithelium since the wavelength used can be adapted to any obstacles that are encountered.

Œdèmes maculaires : définitions et concepts de base

L’œdeme maculaire est lie a l’accumulation de fluide dans les couches retiniennes, tout autour de la fovea. Cet œdeme contribue a une diminution de vision liee a l’alteration des relations fonctionnelles cellulaires au sein de la retine et entraine une reaction inflammatoire secondaire.

Efficacy of pegaptanib sodium in occult or minimally classic

Purpose Recent studies have highlighted the efficacy of Pegatanib sodium in sub-epithelial, occult, CNV seen in the early stages of the disease. n n n nMethods This was a prospective study with a follow-up of 24 months. Patients underwent a complete examination including ETDRS visual acuity measurements, fundus photographs, FA and ICG-A and OCT, as well as treatment by intra-vitreous injection every 6 weeks. n n n nResults 24 patients (16 women) presenting with exudative ARMD were chosen. The mean age was 76 years. 8 eyes had a sub-epithelial occult without classic neovascular lesion, or minimally classic. 8 eyes had a neovascular lesion of pre-epithelial type, predominantly classic. 4 eyes had a neovascular lesion of chorio-retinal anastomosis (CRA) associated with a PED. 4 lesions were fibro-vascular in type. At the end of the study, 100% of pure, occult type or « minimally classic » lesions presented with a loss of less than 15 letters of VA and in 25% of cases there was an improvement of 15 letters or more. Six out of eight treated patients did not lose any letter and five patients had an improvement of at least one letter. These patients had an initial VA of 20/100 or more. FA did not demonstrate any leakage in six cases, and OCT demonstrated an absence of intra-retinal edema in all cases. Out of the 16 patients who presented with a « predominantly classic » or with CRA or with fibro-vascular type lesion, only 3 had an improvement of at least one letter compared with 10 who had the loss of more than 15 letters of VA. Patients in younger age brackets had the better functional results. n n n nConclusion Treatment with Pegaptanib sodium is indicated preferentially for occult or minimally classic type lesions, which are recent and small.