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In vitro experiment to elucidate the mechanism of the ‘soft shell technique’ for preventing subretinal migration of perfluoro-octane
  1. Yau Kei Chan1,2,
  2. Yongjie Lu1,
  3. Gabriela Czanner2,3,
  4. Jing Wu1,
  5. Ho Ching Cheng1,
  6. Rumana Hussain4,
  7. Taiji Sakamoto5,
  8. Ho Cheung Shum1,
  9. David Wong2,4
  1. 1Department of Mechanical Engineering, University of Hong Kong, Hong Kong, Hong Kong
  2. 2Department of Eye and Vision Science, University of Liverpool, Liverpool, UK
  3. 3Department of Biostatistics, University of Liverpool, Liverpool, UK
  4. 4St Paul's Eye Unit, Royal Liverpool University Hospital, Liverpool, UK
  5. 5Department of Ophthalmology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan
  1. Correspondence to Professor David Wong, Consultant Ophthalmologist, St Paul's Eye Unit, 2z link, Royal Liverpool University Hospital, Prescot Street, Liverpool L7 8XP, UK; shdwong{at}gmail.com

Abstract

Aim Perfluorocarbon liquid (PFCL) can migrate into subretinal space in detached and stiffened retina with open holes during vitreoretinal surgery. An innovative ‘soft shell’ technique was introduced to reduce the complication using hyaluronate (HA) to ‘cover’ the retinal hole. This study aims to study the effectiveness of this technique in vitro.

Methods Ex vivo porcine retina was mounted on a transwell insert. Beneath the retina was an aqueous solution. Two retinal holes were made using needle punctures. One of the two retinal holes was covered with HA. Perfluoro-n-octane (PFO) was added above the retina incrementally using a syringe pump. The height of PFO required to cause the migration of PFO through the retinal holes was measured. The ‘pendant drop’ method was carried out to measure the interfacial tensions between the PFO and aqueous, and between PFO and four different concentrations of HA solution.

Results A statistically higher PFO level was required to cause the migration of PFO through the retinal hole with HA coating than without HA coating (Tobit regression with p<0.05). The use of HA was associated with 2.39-fold increase in hydrostatic pressure before the collapse of the PFO interface at the retinal holes. The interfacial tension between PFO and HA solution with concentrations of 0.05%, 0.25%, 0.5% and 1% were 54.2±0.6, 55.3±0.6, 59.5±1.5 and 68.3±1.3 mN/m, respectively (mean±SD). The interfacial tension between PFO and aqueous with 1% HA coating (68.3±1.3 mN/m) was significantly higher than that without (37.4±3.4 mN/m) (p<0.05).

Conclusions The interfacial tension between HA and PFO is higher than that between aqueous and PFO. This is a plausible physical explanation of how the ‘soft shell’ technique might work to prevent subretinal migration of PFCL.

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Footnotes

  • Contributors YKC designed and performed the experiments, collected experimental data, cleaned and analysed the data and drafted and revised the paper. He is guarantor. YL designed and performed the experiments, collected experimental data and drafted and revised the paper. GC performed the statistical data analysis, drafted and revised the paper. JW and HCC performed the experiments and collected experimental data and drafted and revised the paper. RH performed the testing of the soft shell technique in human patients. She has collected video recordings to illustrate soft shell technique. These videos were planned to be submitted with paper. TS is the inventor of the soft shell technique. He has contributed to the hypothesis formation, specifically on the mechanism of interaction between PFO and hyaluronate. HCS monitored data collection for the experiments and drafted and revised the paper. DW initiated the collaborative project, designed the experiments, monitored data collection for the experiments, analysed the data and drafted and revised the paper. He is the clinical and laboratory lead.

  • Funding University of Hong Kong (Seed Funding for Incubating Group-based Collaborative Research Projects).

  • Competing interests This work has been presented in part at the 2016 European Association for Vision and Eye Research Conference (EVER 2016) in Nice, France, on 5–8 October 2016.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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