Conjunctival carriage of SARS-CoV-2 using serial sampling: risk factors and protective factors.

Abstract Objective The conflicting results of conjunctival carriage of SARS-CoV-2 in the current literature may be due to variabilities in sampling technique and sampling time window. In this study we set out to standardize the sampling times and sampling technique to minimize the risk of false negative results. Design A prospective observational study. Method Thirty-nine consecutive COVID-19 patients admitted to a regional hospital in Hong Kong underwent 2 serial conjunctival swabs for reverse transcription–polymerase chain reaction analysis (1 on admission and another before discharge). Using clear instructional video, standardized technique for conjunctival sampling was adopted. Patient's medical history, ocular symptoms, nasopharyngeal SARS-CoV-2 results and personal hygiene habits were prospectively collected and analyzed. Results The majority had mild to moderate COVID-19 disease (89.74% of study participants); 15.38% reported symptoms suggestive of ocular surface inflammation, including epiphora (10.25%), itchiness (7.69%), and foreign body sensation (5.13%). Only 1 patient (2.56%) had bilateral overt conjunctivitis. There was no correlation between the COVID-19 severity and ocular symptoms. Despite obtaining adequate samples, SARS-CoV-2 was not detected in all 78 conjunctival samples. Conclusion Even after adoption of standardized sampling technique, our study could not detect conjunctival carriage of SARS-CoV-2 in patients with mild to moderate COVID. However, our group of patients practiced good personal hygiene, with universal masking, frequent hand washing, and mobile phone sanitation. Further studies to investigate the contribution of personal hygiene on conjunctiva transmission and self-inoculation is warranted.