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

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). 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. 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. 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.