Interdigitation and Ellipsoid Zones Disruption Correlate with Visual Outcomes among Treatment-Naive Patients with Diabetic Macular Edema

Introduction: We have recently shown that defects in interdigitation and ellipsoid zones (IZ and EZ) can predict response to anti-VEGF therapy in a small group of treatment-naive diabetic macular edema (DME) patients. The aim of the current study is to further evaluate this association in a larger study group of patients over a longer follow-up time.

Methods: Thirty eyes of 30 treatment-naive DME patients were analyzed in this retrospective study. The integrity of foveal IZ and EZ was evaluated using optical coherence tomography at the diagnosis of DME and following anti-VEGF injections. The defect size was correlated with best-corrected visual acuity (BCVA) and central macular thickness (CMT).

Results: The mean patients' age at baseline was 63.0 ± 10.0 years. Patients underwent 3.9 ± 2.9 anti-VEGF injections for a mean of 9.1 ± 4.8 months. Following treatment, the mean Snellen visual acuity (VA) improved from 20/52 to 20/44 (p = 0.05), CMT decreased from 432.5 ± 141.4 μm to 375.2 ± 121.4 µm (p = 0.05) and IZ/EZ defect size decreased from 259.83 ± 375.94 µm to 65.34 ± 143.97 µm (p = 0.001). In patients with no IZ/EZ defects at baseline, the mean Snellen VA was better when compared to those with IZ/EZ defects (20/36 vs. 20/70, p = 0.031). The number of eyes with IZ/EZ defects decreased from 17 (57%) at baseline to 6 (20%) at end of follow-up (p < 0.01). BCVA gain correlated with IZ/EZ defect size reduction (r = 0.41, p = 0.02) but not with improvement in CMT (r = 0.28, p = 0.121).

Conclusions: IZ/EZ defect size correlated not only with baseline BCVA but also predicted the change in BCVA after anti-VEGF treatment. Possible future automatic measurement of IZ/EZ defect size might prove helpful for the evaluation of treatment response.