Viscosity matters: OCTA assessment of retinal microcirculation under silicone oil tamponade

This retrospective observational cohort study utilized in situ optical coherence tomography angiography (OCTA) to directly compare the early retinal and choroidal microvascular effects of 1000- and 5000-centistoke (cSt) silicone oil tamponades in a silicone-filled globe following pars plana vitrectomy for macula-on rhegmatogenous retinal detachment.

A total of 64 eyes of 64 patients were included. Patients were grouped by silicone oil viscosity (1000 cSt, n=32 vs. 5000 cSt, n=32) using propensity score matching. OCTA imaging was performed at postoperative weeks 1, month 1, and month 3. Primary outcomes included retinal vessel densities, foveal avascular zone area, choriocapillaris flow, and subfoveal choroidal thickness.

Best-corrected visual acuity improved significantly in both groups, but better visual outcomes were observed in the 1000-cSt group. The 5000-cSt group experienced transient early intraocular pressure elevation. OCTA demonstrated greater reductions in retinal vessel densities (e.g., DCP-Whole VD at Month 3: 50.96 ± 7.07% in 1000-cSt vs. 47.45 ± 6.9% in 5000-cSt), increased foveal avascular zone enlargement (0.318 ± 0.133 mm² in 1000-cSt vs. 0.367 ± 0.153 mm² in 5000-cSt), and more pronounced decreases in choriocapillaris flow (13.76 ± 1.58 mm² vs. 13.02 ± 1.76 mm²) and subfoveal choroidal thickness (285.05 ± 77.34 µm vs. 251.51 ± 73.61 µm) in the high-viscosity (5000-cSt) group (all p<0.05).

Silicone oil viscosity significantly influences early postoperative retinal and choroidal perfusion. In situ data directly comparing viscosities show that high viscosity silicone oil is associated with greater microvascular compromise, making viscosity a critical factor in endotamponade selection.