Sequential restoration of external limiting membrane and ellipsoid zone after intravitreal anti-VEGF therapy in diabetic macular oedema.

Background/objectives: To study the mechanism of restoration of retinal photoreceptor ellipsoid zone (EZ), after intravitreal bevacizumab (IVB) therapy, in diabetic macular oedema (DMO).

Subjects/methods: Forty-four consecutive patients aged 40-65 years having type 2 diabetes mellitus (DM) with DMO were prospectively recruited for IVB therapy. It comprised of three doses (1.25 mg in 0.05 ml) of IVB at monthly intervals. Patients with other ocular and systemic diseases affecting retinal vessels and earlier ophthalmological interventions were excluded. Visual acuity (logMAR VA) was recorded. Spectral domain optical coherence tomography (SD-OCT) was performed pre and post intervention. Central sub-foveal thickness (CST) and grades of disorganization of retinal inner layers (DRIL), external limiting membrane (ELM) and EZ were assessed. Data were statistically analysed on SPSS software. Clinical trials registry: CTRI/2019/03/018135.

Results: Mean logMAR VA decreased after IVB therapy from 1.78 ± 0.07 pre-intervention to 0.42 ± 0.05 post intervention (p < 0.001). Similarly, CST reduced from 354.23 ± 15.0 µm pre-intervention to 233.18 ± 7.88 µm post intervention (p < 0.001). Among qualitative variables, DRIL decreased from 93.2% pre-intervention to 13.6% post intervention. Likewise, global ELM disruption reduced from 81.8 to 9.1% and global EZ disruption reduced from 79.5 to 11.4%. ELM restoration preceded EZ restoration.

Conclusion: Anti-VEGF therapy restores the barrier effect of ELM. It causes ELM to restore first followed by EZ restoration in DMO.