SARS-CoV-2 and the ocular surface: test accuracy and viral load.

Area of Science:

• Ophthalmology
• Infectious Diseases
• Molecular Diagnostics

Background:

• Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can cause coronavirus disease 2019 (COVID-19).
• Ocular surface involvement in COVID-19 is a growing area of research.
• Accurate detection of SARS-CoV-2 in ocular samples is crucial for understanding transmission and disease management.

Purpose of the Study:

• To evaluate the presence of SARS-CoV-2 RNA on the ocular surface in individuals with suspected COVID-19.
• To determine the accuracy of ocular surface molecular testing (Schirmer test and conjunctival swab/cytology) compared to nasopharyngeal swabs.
• To assess the correlation between ocular findings and ocular SARS-CoV-2 RNA detection.

Main Methods:

• 152 individuals with suspected COVID-19 underwent simultaneous nasopharyngeal and ocular surface sampling (Schirmer test and conjunctival swab/cytology).
• Quantitative reverse-transcriptase polymerase chain reaction (RT-qPCR) was used to detect SARS-CoV-2 RNA.
• Slit lamp biomicroscopy was performed to assess ocular manifestations.

Main Results:

• 86 (56.6%) of 152 patients had COVID-19 confirmed by nasopharyngeal PCR.
• Both Schirmer (16.3%) and conjunctival swab (17.4%) tests detected SARS-CoV-2 RNA, with no significant difference between them.
• No ocular SARS-CoV-2 RNA was detected in patients with negative nasopharyngeal PCR.
• Viral load (Ct values) was significantly lower in ocular samples compared to nasopharyngeal samples.
• Ocular manifestations were not associated with ocular RT-PCR positivity.

Conclusions:

• Schirmer and conjunctival swab tests are comparably accurate for detecting SARS-CoV-2 RNA on the ocular surface.
• Ocular surface testing can aid in COVID-19 diagnosis, though sensitivity is lower than nasopharyngeal testing.
• The viral load in ocular samples is substantially lower than in nasopharyngeal samples.