# The prone position in COVID-19 impacts the thickness of peripapillary retinal nerve fiber layers and macular ganglion cell layers

## TL;DR

Placing COVID-19 patients in the prone position affects retinal layers, but does not increase eye-related health risks.

## Contribution

This study is the first to investigate how the prone position affects retinal nerve fiber and ganglion cell layers in COVID-19 patients.

## Key findings

- The prone position in COVID-19 patients leads to early loss of peripapillary retinal nerve fiber layer thickness.
- No significant differences in retinal nerve fiber layer thickness were found between prone and non-prone groups at three follow-ups.
- The macular ganglion cell layer was thinner in non-prone patients compared to controls at 1 and 6 months.

## Abstract

The prone position reduces mortality in severe cases of COVID-19 with acute respiratory distress syndrome. However, visual loss and changes to the peripapillary retinal nerve fiber layer (p-RNFL) and the macular ganglion cell layer and inner plexiform layer (m-GCIPL) have occurred in patients undergoing surgery in the prone position. Moreover, COVID-19-related eye problems have been reported. This study compared the p-RNFL and m-GCIPL thicknesses of COVID-19 patients who were placed in the prone position with patients who were not. This prospective longitudinal and case-control study investigated 15 COVID-19 patients placed in the prone position (the “Prone Group”), 23 COVID-19 patients not in the prone position (the “Non-Prone Group”), and 23 healthy, non-COVID individuals without ocular disease or systemic conditions (the “Control Group”). The p-RNFL and m-GCIPL thicknesses of the COVID-19 patients were measured at 1, 3, and 6 months and compared within and between groups. The result showed that the Prone and Non-Prone Groups had no significant differences in their p-RNFL thicknesses at the 3 follow-ups. However, the m-GCIPL analysis revealed significant differences in the inferior sector of the Non-Prone Group between months 1 and 3 (mean difference, 0.74 μm; P = 0.009). The p-RNFL analysis showed a significantly greater thickness at 6 months for the superior sector of the Non-Prone Group (131.61 ± 12.08 μm) than for the Prone Group (118.87 ± 18.21 μm; P = 0.039). The m-GCIPL analysis revealed that the inferior sector was significantly thinner in the Non-Prone Group than in the Control Group (at 1 month 80.57 ± 4.60 versus 83.87 ± 5.43 μm; P = 0.031 and at 6 months 80.48 ± 3.96 versus 83.87 ± 5.43 μm; P = 0.044). In conclusion, the prone position in COVID-19 patients can lead to early loss of p-RNFL thickness due to rising intraocular pressure, which is independent of the timing of prone positioning. Consequently, there is no increase in COVID-19 patients’ morbidity burden.