Assessing bulk emulsification at the silicone oil - saline solution interface in a 3D model of the eye

Refinements in the use of silicone oil as an intraocular tamponade

It is over 60 years since Paul Cibis et al. reported the experimental use of liquid silicone in the surgical management of retinal detachment. Initial experiences were complicated by significant side-effects associated with the impurities in the non-medical grade commercial silicone oils deployed at the time. These were substantially reduced (but not eliminated) by the adoption of refined high-viscosity medical grade silicone oils. Two of the major complications associated with silicone tamponade are (i) the variability of focus due to its movement and higher refractive index, and (ii) progressive emulsification, particularly with low viscosity oils. This article reviews recent and ongoing research on the causes of emulsification of intra-ocular silicone oil to understand the causes better and thereby reduce this risk, especially for those eyes where permanent tamponade is the only current option for retaining vision.

Can wall shear-stress topology predict proliferative vitreoretinopathy localization following pars plana vitrectomy?

We numerically study the fluid dynamics of oil tamponade in models of vitrectomized eyes prompted by a subset of daily activities corresponding to movements on the horizontal plane with the patient in a standing position. Bulk flow features are related to near-wall flow topology and transport at the retinal surface through a wall shear-stress-based analysis. Proliferative VitreoRetinopathy (PVR) is the leading cause of retinal re-detachment occurring in about 20% of all cases due to the accumulation of inflammatory cells in discrete retinal regions. Signalling soluble mediators stimulate inflammatory cells' chemotaxis and studying their distribution across the retinal surface may acquire clinical relevance. In all the investigated cases, persistent and elongated regions along the retina, potentially prone to accumulate chemo-attractants and cells are observed. Gradients of soluble inflammation mediators present in the aqueous are known responsible for the so-called epithelial-mesenchymal transition that initiates PVR and favours recurrent retinal detachment prompting the proliferation of inflammatory cells with collagen matrix deposition and its contraction. The surgical apposition of encircling scleral buckling elements, known for over a century to influence PVR formation and localization, modifies the attracting regions, possibly causing an accumulation of molecules and cells along approximately vertical lines that follow the rising menisci due to the cerclage indentation. The resulting spatial pattern is compatible with clinical observations. This study may open toward rational analyses of near-wall transport to predict PVR pathogenesis by relating biochemical accumulation in certain areas of the retina to clinical conditions.

Corneal Astigmatism Alteration after Combined Silicone Oil Removal and Cataract Surgery with Intraocular Lens Implantation

Purpose

To explore short-term changes in corneal astigmatism after combined silicone oil removal and cataract (SORC) surgery.

Methods

We enrolled 89 patients (43 men and 46 women). Zeiss IOLMaster was used to measure corneal astigmatism status and axial length on the day before and after the SORC surgery. Best-corrected visual acuity (BCVA) and intraocular pressure (IOP) were recorded. The results were compared to the outcomes at 3 days, 1 week, and 1 month postoperatively.

Results

Compared to baseline, K1 decreased significantly at 3 days postoperatively (P = 0.016), 1 week (P = 0.009), and 1 month (P = 0.035), while K2 increased significantly at 3 days postoperatively (P = 0.002), 1 week (P < 0.001), and 1 month (P = 0.001), as well as corneal astigmatism (all P < 0.001). Compared to that at the baseline, BCVA significantly improved at 3 days, 1 week, and 1 month postoperatively (all P < 0.001). Meanwhile, IOP decreased significantly at 3 days postoperatively (P < 0.001), 1 week (P = 0.005), and 1 month (P = 0.007). Similarly, axial length decreased at all follow-up time points (all P < 0.001).

Conclusion

Corneal astigmatism increased in the short term after the SORC operation but gradually decreased at 1 month postoperatively. BCVA improved steadily, and SORC was widely used in the clinic.

Biocompatibility of intraocular liquid tamponade agents: an update

Intraocular liquids tamponade agents, such as perfluorocarbon liquids (PFCLs), semifluorinated alkanes (SFAs), silicone oils (SOs) and heavy silicone oils (HSOs), are a crucial intraoperative and/or postoperative tool in vitreoretinal surgery, in particular for the management of complex vitreoretinal diseases. However, their use is not without complications, which are potentially severe. Consequently, a growing interest has been devoted to the biocompatibility of these compounds and the adequacy of current regulations that should guarantee their safety. Obviously, an updated knowledge on research findings and potential risks associated to the use of intraocular liquid compounds is essential, not only for vitreoretinal surgeons, but also for any ophthalmologist involved in the management of patients receiving intraocular liquid tamponades. In light of this, the review provides a comprehensive characterisation of intraocular liquid tamponades, in terms of physical and chemical properties, current clinical use and possible complications. Moreover, this review focuses on the safety profile of these compounds, summarising the existing regulation and the available evidence on their biocompatibility.