Investigation of the biomechanical changes at the iris-lens interface after vitrectomy with silicone oil tamponade: Insights from ultrasound biomicroscopy

This prospective cohort study investigated anterior segment biomechanical alterations and lens stability using ultrasound biomicroscopy (UBM) in 60 eyes (58 patients) undergoing pars plana vitrectomy (PPV) with silicone oil (SO) tamponade for rhegmatogenous (18 eyes) or diabetic tractional retinal detachment (42 eyes). UBM parameters, including central corneal thickness (CCT), anterior chamber depth (ACD), lens vault (LV), angle-opening distance (AOD500), trabecular-iris angle (TIA), iris-lens angle (ILA), and iris-lens contact distance (ILCD), were assessed preoperatively and 3 months postoperatively. Significant postoperative reductions were observed in CCT (-0.026 mm, P = 0.005), superior ILCD (0.921→0.730 mm, P = 0.006), inferior ILCD (0.914→0.702 mm, P = 0.002), and mean ILCD (0.947→0.745 mm, P = 0.001). The inferior ILA increased (20.31°→23.39°, P = 0.032), while the temporal ILA decreased (20.70°→18.29°, P = 0.047). Subgroup analysis comparing normotensive and hypertensive eyes revealed significant differences in nasal ΔILA (P = 0.008) and temporal ΔILCD (P = 0.014). Multiple regression identified a negative correlation between intraocular pressure (IOP) and nasal ΔILA (β = -0.353, P = 0.002). The findings demonstrate that PPV with SO tamponade induces significant biomechanical alterations at the iris-lens interface, compromising lens stability, and provide valuable anatomical insights for optimizing cataract surgery in SO-filled eyes.