Islets persisting on OCT macular thickness map after intravitreal injections unmask telangiectatic capillaries (TelCaps) in diabetic macular edema

PURPOSE: Recurrence of macular edema after intravitreal injections (IVI) may result from persistent focal microvascular abnormalities such as telangiectatic capillaries (TelCaps), which can be difficult to detect within a thickened retina. This study proposes a simple screening strategy to identify TelCaps using optical coherence tomography (OCT) thickness maps following anti-VEGF treated for diabetic macular edema (DME). METHODS: This is an ancillary study from the TalaDME double-blind randomized controlled trial evaluating the benefit of adjunctive focal laser photocoagulation to anti-VEGF therapy in eyes with DME and TelCaps. OCT imaging was performed monthly and indocyanine green angiography (ICGA) quarterly over 12 months. Twenty-eight fellow eyes that had recovered from center-involved DME (CI-DME) associated with TelCaps were analyzed. TelCaps were identified as late-phase hyperfluorescent lesions on ICGA. The topography of perifoveal retinal thickening on OCT and its spatial correlation with TelCaps were assessed. RESULTS: Following IVI induced resolution of central DME (defined as central macular thickness < 315 µm), OCT mapping revealed 52 perifoveal thickening spots, herein referred to as islets. TelCaps were located within 100 µm of the barycenter of 47/52 (90%) islets, observed in 27/28 (98%) eyes. During follow-up, 25 (89%) eyes showed islets enlargement, with 20 (71%) progressing to involve the fovea. All cases of central DME recurrence occurred in eyes with post-IVI islets, and recurrent edema was topographically continuous with these islets. No recurrence was observed in eyes with documented TelCaps occlusion. CONCLUSION: Following anti VEGF treatment for CI-DME associated with TelCaps, OCT thickness mapping can reveal islets of retinal thickening that frequently colocalize with residual TelCaps, potentially heralding recurrence of central edema. A systematic search for these islets may facilitate the diagnosis of TelCaps.