The Soft Shell Technique To Prevent Leakage of Perfluorocarbon Liquid Into The Subretinal Space

Purpose
Perfluorocarbon liquid (PFCL) can be used to unfold the retina during vitreoretinal surgery. The subretinal migration of PFCL is an undesirable complication of its use in cases with posterior retinal breaks particularly with associated proliferative vitreoretinopathy. The ‘soft shell’ technique, which is the use of hyaluronate (HA) to cover the break, has been described to prevent such migration. Our aim is to assess the scientific basis of this technique.

Methods
A porcine retina model with two holes on a transwell was used to mimic the retinal breaks in vivo. HA solution was used to cover one of the holes. Perfluoro-n-octane (PFO) was added on top of the retina model incrementally using a syringe pump. The liquid level of PFO required to cause rupture of the PFO/aqueous interface with or without the HA coating at the two holes was measured. The interfacial tensions between the PFO against water and against HA solution with different aqueous concentrations were measured using pendant drop analysis.

Results
The interfacial tension between PFO and aqueous with HA coating (68.3 ± 1.29 mN/m) is statistically significant higher than the PFO/aqueous interface without hyaluronate (37.4 ± 3.40 mN/m) (p < 0.05). A higher PFCL level is required to cause the rupture of the PFO/aqueous interface at the hole with HA coating.

Conclusions
A greater hydrostatic pressure is needed to rupture the PFO/aqueous interface in the presence of HA coating at the break. The increase may due to the increase in interfacial tension at the interface. This study provides the scientific explanation how the soft shell technique may work.

© 2016 Acta Ophthalmologica Scandinavica Foundation