Retinal surgery risks and COVID-19
As the COVID-19 pandemic highlights the risks of infection caused by aerosol-generating procedures, a new study has found that a common sight-saving eye surgery is unlikely to produce aerosols.
A retinal detachment places a patient at risk of permanent vision loss and is one of the most common reasons for an emergency eye surgery.
“When a patient with a retinal detachment arrives at the emergency department experiencing flashes of light or a sudden loss of vision, it is a serious situation that often requires an urgent operation,’’ explains Royal Victorian Eye and Ear Hospital (RVEEH) vitreoretinal fellow Dr Mali Okada.
The retina is a thin layer of light-sensing cells at the back of the eye which enable us to see. It is held in place by the vitreous, a balloon of clear jelly which gives the eye its shape and transmits light to the retina.
As we get older our vitreous shrinks, which can tear at the retina and cause holes which fill with fluid and cause it to peel away from its supporting structures.
“It is like the wallpaper lining of the eye that is peeling away,’’ says Dr Okada.
To treat a retinal detachment, surgeons perform a vitrectomy, a procedure using a tiny, high-speed instrument which removes the vitreous gel in order to re-attach the retina.
The technique is also used for other surgeries that affect the retina, like haemorrhages caused by diabetic retinopathy and holes in the macula.
Aerosols and surgery
The COVID-19 pandemic has highlighted the increased risks from surgical procedures which generate aerosols – tiny airborne particles and droplets which can increase the likelihood of viral transmission.
Early in the pandemic, studies focused on the aerosol-generating potential of operations using high-speed bone and dental drills.
Novel coronavirus has been isolated in tears and the conjunctiva, however, it has been unclear whether vitrectomy surgery generates aerosols and therefore places operating room staff at higher risk of transmission.
But now a new research by the Centre for Eye Research Australia and RVEEH suggests that using current techniques aerosol generation is unlikely.
The study, published in Ophthalmology Retina, measured droplet and particle levels in lab-based experiments and 18 retinal surgeries performed at the RVEEH.
It is believed to be the first study to quantify aerosol generation from human vitrectomies conducted in real-life conditions – and the findings are consistent with previous research using plastic models or cadavers.
In the current study, the vitrectomy was performed by making three small holes in the front of the eye and inserting tiny valved ports to enable instruments used in the operation – including the vitrectomy cutter – to access the interior of the eye.
“A vitreous cutter is a needle like instrument used to remove vitreous. It cuts at a very high speed of up to 10,000 cuts per minute and is capable of generating aerosol particularly as it is operated within the fluid- filled posterior chamber of the eye,’’ says vitreoretinal surgeon Jonathan Yeoh.
“We wanted to answer the question whether any aerosol that was potentially being generated by the vitreous cutter could then be released from the eye.”
The surgeons’ interest kick-started a collaboration with colleagues from CERA, who supported the research effort in the lab and with study design.
“It was a great opportunity to respond to the challenges of COVID-19 and collaborate with our colleagues to investigate a highly important and timely question about their practice,’’ says CERA Deputy Director Associate Professor Peter van Wijngaarden.
“A key part of our partnership with the RVEEH is our shared commitment to conducting research that will make a difference to patient care.’’
The resulting study included a series of three experiments, including one which involved placing particle counters about 30cm from eye level during 18 standard vitrectomy surgeries to measure aerosol and droplet counts at key points of the operation.
The results found that no significant increase of droplet or particle counts around the surgical field when the high-speed instruments were used.
Impact on practice
Dr Okada says the results of the study show that the risk of valved-port vitrectomy generating aerosols is low.
She says these findings can give surgeons a level of confidence that they do not need to modify techniques or introduce additional protective measures to mitigate against aerosol generation.
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You can read the full study
Vitrectomy as an Aerosol generating Procedure in the time of COVID-19: The VAPOR Study Mali Okada, MMed, FRANZCO, David C. Sousa, MD, David CA. Fabinyi, FRANZCO, Xavier Hadoux, PhD, Thomas L. Edwards, PhD, FRANZCO, Karl D. Brown, PhD, Daniel Chiu, FRANZCO, Rosie CH. Dawkins, MPH, FRANZCO, Penelope J. Allen, FRANZCO, Jonathan Yeoh, FRANZCO, Peter van Wijngaarden, PhD, FRANZCO, Ophthalmology Retina