The Influence of Anti-VEGF Agents on Intra-Retinal Lipo-Protein Exudates Assessed by Spectral Domain and Polarisation Sensitive Optical Coherence Tomography

Abstract

Purpose: : Hyperreflective intra-retinal foci visible in spectral domain optical coherence tomography (SD OCT) and associated with diabetic macular edema (DME) have been described previously as precursors of hard exudates. Polarisation sensitive OCT (PS OCT) allows raster scanning of the retina enabling to detect, map and measure retinal structures, such as microexudates, based on their polarization scrambling qualities. The current study was performed to analyse the changes in distribution and morphology of intraretinal microexudates in DME following monthly treatment with intravitreal anti-VEGF agents based on SD OCT and PS OCT examinations.

Methods: : Fifteen patients with persistent clinically significant macular edema due to diabetes mellitus were included in this prospective study. Patients received 3 intravitreal injections with either 1.5mg bevacizumab or 0.5mg ranibizumab in monthly intervals. The localisation of hyperreflective exudative foci and hard exudates in the central retinal area was analyzed monthly by SD OCT and PS OCTand fundus photography.

Results: : Intravitreal treatment with anti-VEGF induced a decrease in central retinal thickness from 390±32 µm to 343±33 µm until month 3. A dynamic change in the distribution pattern of microexudates was observed in SD OCT. In PS OCT, microexudates were detected and segmented automatically allowing a three-dimensional observation of their therapeutically induced dynamic changes in intra-retinal distribution. With decrease of retinal thickness single microexudates either resolved or accumulated in groups of hyperreflective foci at the border of the outer nuclear and outer plexiform layer. Once accumulated they became visible as hard exudates in fundus photography. This phenomenon of hard exudate formation could be observed in a very short time period, such as 3 days, according to the fast decrease in retinal thickness.

Conclusions: : Anti VEGF agents cause a short-term decrease in retinal thickness and induce a significant and fast change in intra-retinal lipoprotein distribution, in some cases leading to hard exudate formation in only 3 days. PS OCT is a novel and valuable technique for the automated detection of intra-retinal microexudates in vivo.

Clinical Trial: : www.clinicaltrials.gov NCT00545870

Keywords: diabetic retinopathy • imaging/image analysis: clinical • lipids