Phacoemulsification and nucleic acid-enriched aerosol: considerations from an eye model of cataract simulation

Abstract

Purpose: The purpose of this study is to investigate whether phacoemulsification can generate aerosolized single-stranded RNA (ssRNA) and retain sequence integrity using an artificial eye model for experimental cataract surgery.

Methods: A simulation of cataract surgery was performed using an anterior chamber eye model filled with an ssRNA probe at different scalar dilutions (kanamycin positive control ssRNA). A plastic conical cage was built over the artificial eye surface of the mock-up. A total of 24 tests (twice reproduced) were performed, and five nitrocellulose strips were placed 15 cm from the artificial surface of the mock-up and used to collect aerosol particles, from each experiment. Phaco-activity was mimicked using a phacoemulsification equipped with a 2.75-mm tip, and strips were removed at the end of the procedure. RNA extraction, reverse transcription, and agarose gel electrophoresis were performed and compared.

Results: Strips collected aerosol droplets enriched with ssRNA, mainly at the higher concentrations tested, compared to related untouched standard solutions. Complementary DNA (cDNA) synthesis confirmed the presence of intact ssRNA fragments. As observed from densitometric analysis of resolved RNA in extracted samples and cDNA bands after retro-transcription, lower concentrations of ssRNA were also detected.

Conclusions: As the main output of the study, the phaco-generated aerosol can deliver an intact ssRNA sequence. Since the aerosol can potentially reach the operator's face, any biological agent (virus/bacteria) potentially inside the anterior chamber of a patient undergoing cataract surgery, eventually escaping from biomolecular checks, can be potentially infective for operators. The data reported herein suggest that collective versus individual protective countermeasures should always be encouraged in ocular surgery and should not be restricted to coronavirus disease emergencies.

Keywords: 3D visual screen; Aerosol; COVID-19; Eye model; Nucleic acids; Personal protective equipment; Phacoemulsification cataract.

Fig. 1

Description of artificial eye model. The simulation of phacoemulsification for cataract surgery was performed in a wet lab using an eye to investigate the possibility of aerosol transmission (A). Overview of the surgical training station used for simulation activity (b). Note that the model is placed on a support specific for the training simulation (C). The eye model is framed (C, green square)

Fig. 2

Probe extraction and cDNA synthesis. Serial single-stranded RNA solutions (dilution factor 2) were introduced into the anterior chamber of the mock-up (400 µL/eye model) and prepared for phacoemulsification experiments. The simulation of phacoemulsification surgery was performed in a wet lab. Spectral absorbance acquisition of standard dilutions (A) and aerosol extracted (B) RNAs; Representative 2% agarose gel (C, E, G) and the related densitometric analysis (D, F, H) of resolved complementary DNA products, previously synthesized from the following: the total RNA standard solutions (C, D), anterior chamber (E, F), and strip/aerosol (G, H) RNAs. From left to right: M, DNA ladder and 1st–6st (st, standard; c); 1c–6c (c, chamber; D) and 1 s–6 s (s, strip; E). Note the absence of signals at lower concentrations. Densitometric analysis was performed using ImageJ software

Fig. 3

Representative 3D-assisted surgery session. Picture depicting a phacoemulsification session in the surgery room. Note that the surgeon was wearing a face shield over 3D glasses (see red arrows in upper left insert), while performing the surgery with a 3D-visualization system (NGENUITY®; Alcon Inc. Technology, Fort Worth, TX, USA). The 3D-display unit consists of a camera, a processing unit, and a display, allowing the surgeon to be far from the ocular surface (see upper left inset). On the right, a surgical display reproduces the operating field in real time. This viewing system improves both the safety and efficiency of cataract surgery during the COVID-19 pandemic