Evaluation of retinal changes after silicone oil removal BY optical coherence tomography angiography in patients underwent vitreoretinal surgery due to macula off rhegmatogenous retinal detachment

Purpose: To evaluate optical coherence tomography angiographic (OCTA) changes of retinal microvascular structure and central macular thickness (CMT) after silicone oil removal (SOR) in patients underwent pars plana vitrectomy (PPV) and silicone oil (SO) injection due to macula off rhegmatogenous retinal detachment (RRD), and to find out the association between OCTA parameters and best corrected visuel acuity (BCVA) scores. Method: This study included 19 patients with macula off RRD who underwent 25 Gauge PPV surgery and 1300 cts SO endotamponade between October 2018 and March 2020 in Dokuz Eylul University Faculty of Medicine, Department of Ophthalmology (Retina Unit). Retinal microvascular structure and CMT were evaluated by OCTA before SOR surgery and postoperative first and fourth week. Sound eyes of study partipicants composed the control group. The correlations between BCVA and OCTA parametres were analyzed at postoperative first month of SOR surgery. Results: The mean age of study participants was 56.47±12.90 years. Mean duration of SO endotamponade was 4.37±2.90 months. Mean BCVA score was found as 0.71±0.27 LogMAR, 0.67±0.24 LogMAR and 0.57±0.23 LogMAR before SOR and postoperative first and fourth weeks, respectively (p=0.03). CMT and FAZ area did not show a significant change after SOR (p=0.082; p=0.219, respectively). Choroidal thickness (CT) score was 203.74± 62.80 μm, 219.05± 76.46 μm and 220.11±70.55 μm before SOR and postoperative first and fourth weeks, respectively (p=0.015). Parafoveal and foveal superficial vascular plexus density (SVPD) and deep vascular plexus density (DVPD) were not found to be significantly different in study eyes at 1 month after SOR (p>0.05). No statistical significant difference was found in CT, FAZ area, foveal SVPD and DVPD between study and fellow eyes. Mean CMT was 211.63± 37.59 μm and 240.32± 25.09 μm in study and fellow eyes at 1 month after SOR surgery. (p=0.023). The superior and inferior parafoveal SVPD scores were 46.46± 4.75, 45.30± 3.33 in the study eyes after first month of SOR, whereas they were found as 47.63± 2.88 ve 47.31± 3.4 in control eyes (p=0.012; p=0.028 respectively). The inferior parafoveal DVPD score was 47.66±4.14 in study eyes, whereas it was found as 50.93± 4.78 in fellow eyes (p=0.031). No statistical correlation was also found between BCVA and analized OCTA parametres. Conclusion: Lower parafoveal vessel density and thinner CMT values were found in eyes with macula off RRD that were successfully treated with PPV and SO injection.There was no statistical significant alteration in retinal microvascular structure in early period after SOR. There was no relationship between BCVA and OCTA parameters including CMT. Key Words: Silicone oil, optical coherence tomography angiography, superficial vascular plexus density, deep vascular plexus density, rhegmatogenous retinal detachment, central macular thickness