GaslEss Macular hole surgery (GEM): a feasibility study

Research Question Is it feasible to conduct a randomised, controlled, non-inferiority trial comparing full-thickness macular hole (FTMH) surgery with and without intravitreal gas tamponade?

Background Pars plana vitrectomy with intraocular gas tamponade has been the standard treatment for FTMHs for the last 30-years.

Gas tamponade has multiple drawbacks: it results in very poor vision for several weeks, limiting patients ability to drive and work; many patients are advised to undertake intensive face-down posturing for about a week after surgery, to float the gas bubble onto the macula; it is cataractogenic and prevents adequate fundus examination; it can elevate intraocular pressure, sometimes precipitously, mandating regular hospital review; patients cannot fly or ascend beyond 300 metres, prohibiting transport home from some vitreoretinal centres; the fluorocarbon tamponades are some of the most potent greenhouse gases – over 100-years 1 kg of equates to releasing 24 metric tonnes of CO2; worse still, this continues for 3,200-years.1 Three uncontrolled retrospective case series have reported promising results utilising novel FTMH surgery without gas tamponade.

Aims and objectives To establish if it is feasible to recruit, retain, and evaluate patients with FTMHs into a larger RCT of vitrectomy without gas tamponade.

The main clinical aim is to collect preliminary safety and efficacy data, comparing gasless vitrectomy with standard vitrectomy with gas.

Methods This prospective, assessor masked, randomised feasibility study aims to recruit 60 participants with FTMH from six NHS sites in England.

Participants will be randomised 1:1 to either standard vitrectomy, gas tamponade and post-operative posturing, or to gasless vitrectomy without posturing.

Gasless surgery involves folding a hinged flap of internal limiting membrane over the hole, secured by gravity and viscoelastic gel.

Participants will attend post-operative day 1, week 1, and months 1, 3 and 6, for examination and optical coherence tomography (OCT) imaging.

The main feasibility outcomes will be recruitment and retention rates, technical success, cross-over, and acceptability of treatment to participants. Patient acceptability questionnaires were added by our patient involvement group.

The main clinical outcomes are primary FTMH closure on OCT at 3 months, best-corrected visual acuity at 6 months, and adverse events.

Timelines for delivery Commencement 1st July 2023; contracting 6 months; site set up 6 months; recruitment 23 months; follow-up 6 months; data lock/cleaning 4 months; data analysis and reporting 4 months.

Anticipated impact and dissemination Whilst surgery is usually effective a closing FTMHs, the burden of recovery on patients, carers, the health service, and the environment remains largely unchanged over 30-years.

If gas tamponade was eliminated from FTMH surgery we contend that, from a patient perspective, this would be the greatest advance since the introduction of vitrectomy in 1991.

The results of this study will determine if a substantive trial of gasless FTMH surgery is feasible, inform its design, and help secure funding.

The findings will be presented at international ophthalmology conferences, provided to participants, shared through eye charity and hospital news channels, and published in specialty medical journals.