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Détection des TelCaps par le mapping OCT dans l'oedème maculaire diabétique

Intravitreal injections (IVI) of anti-vascular endothelial growth factor (anti-VEGF) agents help reducing macular thickness in patients with diabetic macular edema (DME), mainly acting on the diffuse component of the blood-retina barrier breakdown. However, they imply long-standing treatment and represent a heavy burden for the patients and the health care system. Anti-VEGF-resistant telangiectatic capillaries (TelCaps) have been reported, which result in persistent focal edema, on which Indocyanine Green Angiography (ICGA) guided laser therapy is effective. In this study, we investigated the qualitative changes in macular thickness visible on OCT-mapping after intravitreal injection of anti-VEGF agents, in eyes with DME and TelCaps.

Unplanned retrospective analysis of prospectively collected data from a French national, multicentric, ongoing randomized, controlled trial evaluating the efficacy of targeted photocoagulation of TelCaps in addition to intravitreal anti VEGF injections in eyes with central involving DME and decreased visual acuity were collected. Ten eyes of 10 patients with Type 2 diabetes (8 males and 2 females, mean age 65 ± 9 years, mean baseline HbA1C 8.3 ± 1.5%) were studied with a 12-months follow-up. After three monthly loading doses of intravitreal injection (IVI) of anti-VEGF agents, a pro re nata regimen was applied.  Patients in the laser group received additional targeted photocoagulation of late ICGA staining TelCaps. ICGA was performed before initiating IVI, and at 3, 6 and 12 months, in addition to monthly optical coherence tomography (OCT). Imaging protocol for OCT and ICGA was performed with Heidelberg Spectralis HRA+ OCT (Heidelberg, Germany). Large macular cube (30x 25°, spacing 60 to 120 µm, HR, ART 1) was performed during late ICG angiography. The location of the TelCaps and the corresponding retinal thickening were determined using the OCT- map overlaid on the ICG images, in modulating the contrast and transparency. Evolution of central macular thickness (CMT), as well as a qualitative analysis of topography of macular thickening over time on OCT-map within a 6-mm diameter macular region were studied.

There was a significant reduction of macular thickness between baseline and 3 months after a loading  dose of three monthly anti-VEGF agents (± adjunctive laser), decreasing from 426±85 µm to 319 ± 99µm. Qualitative analysis of the OCT-mapping revealed that macular edema associated with Telcaps was often asymmetrical and polylobulate. TelCaps were easily identified after IVI, because residual patches of retinal thickening systematically colocalized with TelCaps visible on late ICGA.  After relative suspension of anti -VEGF (PRN regimen from 3 to 12 months), new increase in retinal thickness systematically emerged from TelCaps, with a similar pattern to the one before IVI.  

In patients with DME, persistent patches of retinal thickening despite repeated IVI may indicate the presence of TelCaps, which are often located under the summit of focal edema, and usually correspond to the center of circinate exudation.

In the absence of ICGA, OCT mapping may be helpful to screen for TelCaps that may then be identified by high resolution OCT imaging, which may guide photocoagulation.