Material and Methods: The study included patients who received loading dose of intravitreal ranibizumab (IVR) forME secondary to unilateral RVO and had no ME in optical coherence tomography (OCT) obtained on month 12. The contralateral eyes of the patients were employed as control. ORLT was measured using automated segmentation feature in OCT. The RVO and control groups were compared regarding ORLT and relationship between ORLT and VA was assessed within RVO group. A p value <0.05 was considered as statistically significant.

Results: The study included 156 eyes of 78 patients. Of the patients, 70.5% had branch RVO and 29.5% had central RVO. There was a significant increase in mean VA on month 12 in the RVO group compared to the baseline (p ?0.01). In the RVO group, dexamethasone (DEX) implant was given to 59% of the patients in addition to IVR. In RVO group, ORL thickness in M, N1, S1 and S2 segments were significantly lower than the control group (p <0.05, all values). The ORL thickness in M, N1, T1, T2, S1 and S2 segments were significantly lower in eyes received at least one DEX implant compared to eyes received no DEX implant (p <0.05, all values). There was a significant correlation between the mean VA value in the RVO group on month 12 and ORL thickness in segment M (p <0.01).

Conclusion: In RVO patients, subfoveal ORLT measured after resolution of ME is thinner in occlusion eyes than in healthy eyes. The significant ORLT decrease in eyes with DEX than in eyes received DEX implant compared to those received no DEX implant can be explained by the fact that DEX was given to patients with a more severe course of ME. The decrease in subfoveal ORLT resulting in lower VA suggested that RVO can lead to photoreceptor and/or retinal pigment epithelium degeneration in the long term. Keywords : Dexamethasone implant, macular edema, OCT, outer retinal layer thickness, ranibizumab, retinal vein occlusion