Rohit Shetty MD, PhD, FRCS
Cataract surgery produces no aerosolisation and is therefore unlikely to spread COVID-19, making it safe to perform with reasonable precautions, according to studies by Professor Rohit Shetty MD, PhD, FRCS, and colleagues from Narayana Nethralaya Eye Hospital, Bangalore, India. A paper based on this research has been accepted for publication in the Journal of Cataract and Refractive Surgery, with Naren Shetty MD the lead author.
For refractive surgery, microkeratomes to cut LASIK flaps splattered droplets widely, making it unsuitable for use, Prof Shetty said. However, femtosecond laser flap cuts, SMILE cuts and photoablation did not produce aerosols that can theoretically spread COVID-19, making them safe for use as well, the studies concluded.
“There are a lot of myths and fear about aerosols pushing doctors to take aggressive precautions, but it is impossible to operate with full PPE. This is a big relief for the surgeon,” Prof Shetty said.
Conducted with assistance from fluid velocimetry scientists at the Indian Institute of Science in Bangalore, the studies examined surgery conducted on artificial anterior chambers and goat eyes in a wet lab model. Fluids were stained with trypan blue to enhance visibility of droplets as small as 20 microns, which were recorded with an ultra-high-resolution camera at 20,000 frames per second.
Surprisingly, no combination of wound size and phaco sleeve diameter produced any visible aerosolisation with phaco operating inside the anterior chamber, Prof Shetty said. And though wounds larger than the sleeve leaked slowly and steadily, no aerosolisation was observed. However, a fixed phaco probe operated against the outer surface of the cornea produced many droplets. Therefore, researchers recommend starting and stopping phaco only with the probe inside the eye.
Performing non-contact tonometry without lubrication produced no visible aerosol, the researchers found. However, adding a drop of lubricant before tonometry did lead to minimal aerosolisation. Therefore, non-contact tonometry should only be performed in normal condition eyes without eyedrops, and should be avoided in watery eyes.
Reassured by this research, Narayana Nethralaya surgeons decided to recommence cataract surgery. High-speed films taken in clinic confirmed that phaco produced no aerosol during procedures.
To further reduce risk, the researchers recommend betadine gargle and nose drops before surgery, as well as preparing the surgical site, to reduce any viral load. Use of viscoelastic on the corneal surface prevents leakage and any potential aerosolisation. Turn irrigation on and off only inside the anterior chamber. Double gowning and disinfection stations inside the operating area are also recommended.
YouTube links to the study findings:
Refractive surgery aerosol study
https://youtu.be/aHH2H8DTI0Q
Cataract surgery aerosol study
https://youtu.be/uFQjpuf7EdE
Non-contact tonometry aerosol study
https://youtu.be/yim9ZRTcZzs
