Visual outcomes and structural optical coherence tomography biomarkers after intravitreal dexamethasone implant for anti-vascular endothelial growth factor-resistant macular edema secondary to retinal vein occlusion
Authors: Saleh Mennatallah G.A. , Abdel-Radi Mahmoud , Ali Omar M. , Saleh Mohamed G.A. , Mostafa Magdi M. 
Published: January 2025

Purpose
This study aimed to evaluate the functional and anatomical outcomes of intravitreal dexamethasone (DEX) implant (Ozurdex) in retinal vein occlusion (RVO)-related macular edema (ME) resistant to anti-vascular endothelial growth factor (anti-VEGF) therapy and to correlate them with certain optical coherence tomography biomarkers.

Patients and methods
This is a prospective interventional study that included 25 eyes of 25 patients with RVO-related resistant ME (15 branch RVO and 10 central RVO), who received six or more consecutive monthly intravitreal injections of anti-VEGF but the central macular thickness (CMT) remained more than 350 µm 4 weeks after the last injection, or when the reduction in the CMT was less than 10% of the baseline. Optical coherence tomography examinations were carried out at baseline and at the 1-, 3-, and 6-month visits after intravitreal DEX implant. The correlation of the corrected distance visual acuity (CDVA) to the CMT, the ratio of the vertical diameter of the largest cyst to the maximum macular thickness (VDLC/MMT), the subfoveal choroidal thickness, and the extent of interruption of ellipsoid zone were evaluated 3 months following the DEX implant injection.

Results
The mean CDVA significantly improved from 0.92±0.25 LogMAR at baseline to 0.59±0.25 LogMAR (P<0.001) at the first month, to 0.49±0.26 LogMAR (P<0.001) at the third month, and to 0.70±0.34 LogMAR (P<0.001) at the sixth month following intravitreal DEX implant injection. The mean CMT significantly improved from 596.08±156.83 μm at baseline to 310.92±80.77 μm (P<0.001) at the first month, to 269.08±62.35 μm (P<0.001) at the third month, and to 433.84±110.75 μm (P<0.001) at the sixth month. The mean subfoveal choroidal thickness significantly decreased from 306.84±50.41 μm at baseline to 274.16±36.88 μm (P=0.001) at the first month, to 256.56±41.56 μm (P<0.001) at the third month, and to 271.72±33.18 μm (P<0.001) at the sixth month following the intravitreal DEX implant. The VDLC/MMT ratio significantly decreased from 0.54±0.17 at baseline to 0.26±0.03 (P<0.001) at the first month and to 0.19±0.03 (P<0.001) at the third month following the intravitreal injection of DEX implant. At the sixth month postinjection, the reduction was insignificant (0.46±0.18, P=0.112). A significant strong negative correlation was found between the extent of the ellipsoid zone interruption and the CDVA after 3 months (r=−0.827, P<0.001). A moderate negative correlation was found between the VDLC/MMT ratio and the CDVA after 6 months (r=−0.424, P=0.035). The mean change in the CMT was significantly correlated with the mean decrease in the CDVA in the central RVO group after 6 months (r=0.800, P=0.010).

Conclusion
Intravitreal DEX implant was an effective and safe management option for RVO-related ME resistant to anti-VEGF therapy. However, after 6 months of follow-up, recurrence of ME was observed in most cases. Significant correlations were found between the change in CDVA and the change in CMT and the baseline VDLC/MMT ratio.