Assessing visible aerosol generation during vitrectomy in the era of Covid-19

ObjectiveTo assess visible aerosol generation during simulated vitrectomy surgery. Methods: A model comprising a human cadaveric corneoscleral rim mounted on an artificial anterior chamber was used. Three-port 25 gauge vitrectomy simulated surgery was performed with any visible aerosol production recorded using high speed 4K camera. The following were assessed: (1) vitrector at maximum cut rate in static and dynamic conditions inside the model, (2) vitrector at air-fluid interface in physical model, (3) passive fluid-air exchange with a backflush hand piece, (4) valved cannulas under air, and (5) defective valved cannula under air. ResultsNo visible aerosol or droplets were identified when the vitrector was used within the model. In the physical model, no visible aerosol or droplets were seen when the vitrector was engaged at the air-fluid interface. Droplets were produced from the opening of backflush hand piece during passive fluid-air exchange. No visible aerosol was produced from the intact valved cannulas under air pressure, but droplets were seen at the beginning of fluid-air exchange when the valved cannula was defective. ConclusionsWe found no evidence of visible aerosol generation during simulated vitrectomy surgery with competent valved cannulas. In the physical model, no visible aerosol was generated by the high-speed vitrector despite cutting at the air-fluid interface.

Reducing visible aerosol generation during phacoemulsification in the era of Covid-19

ObjectiveTo assess potential methods of reducing visible aerosol generation during clear corneal phacoemulsification surgery in the era of Covid-19. MethodsAerosol generation during phacoemulsification was assessed using a model comprising a human cadaveric corneoscleral rim mounted on an artificial anterior chamber. Typical phacoemulsification settings were used and visible aerosol production was recorded using high speed 4K camera. Aerosolisation was evaluated under various experimental settings: Two different phacoemulsification tip sizes (2.2mm, 2.75mm), varying levels of corneal moisture, the use of suction and blowing air in the surgical field, the use of hydroxypropyl methylcellulose (HPMC) coating of the cornea with a static and moving tip. ResultsThis model demonstrates visible aerosol generation during phacoemulsification with a 2.75mm phacoemulsification tip. No visible aerosol was noted with a 2.2mm tip. The presence of visible aerosol is unrelated to corneal wetting. Suction in close proximity to the aerosol plume did not impact on its dispersion. Blowing air redirected the aerosol plume towards the ocular surface. Visible aerosol production was abolished when HPMC was used to coat the cornea. This effect lasted for an average of 67{+/-}8 seconds in the static model. Visible aerosol generation was discerned during movement of the 2.2mm tip towards the corneal wound. ConclusionsWe demonstrate visible aerosol production in the setting of a model of a clear cornea phacoemulsification. Visible aerosol can be reduced using a 2.2mm phacoemulsification tip and reapplying HPMC every minute during phacoemulsification.