Background: Antibiotic eye drops are frequently used in clinical practice. Due to the anatomical connection via the nasolacrimal duct, it seems possible that they have an influence on the nasal/pharyngeal microbiome. This was investigated by using two different commonly used antibiotic eye drops. Methods: 20 subjects were randomized to four groups of five subjects receiving eye drops containing gentamicin, ciprofloxacin, or, as controls, unpreserved povidone or benzalkonium chloride-preserved povidone. Nasal and pharyngeal swabs were performed before and after the instillation period. Swabs were analyzed by Illumina next-generation sequencing (NGS)-based 16S rRNA analysis. Bacterial culture was performed on solid media, and bacterial isolates were identified to the species level by MALDI-TOF MS. Species-dependent antimicrobial susceptibility testing was performed using single isolates and pools of isolates. Results: Bacterial richness in the nose increased numerically from 163 ± 30 to 243 ± 100 OTUs (gentamicin) and from 114 ± 17 to 144 ± 45 OTUs (ciprofloxacin). Phylogenetic diversity index (pd) of different bacterial strains in the nasal microbiome increased from 12.4 ± 1.0 to 16.9 ± 5.6 pd (gentamicin) and from 10.2 ± 1.4 to 11.8 ± 3.1 pd (ciprofloxacin). Unpreserved povidone eye drops resulted in minimal changes in bacterial counts. Preservative-containing povidone eye drops resulted in no change. A minor increase (1–2-fold) in the minimal inhibitory concentration (MIC) was observed in single streptococcal isolates. Conclusions: Antibiotic eye drops could affect the nasal microbiome. After an instillation period of seven days, an increase in the diversity and richness of bacterial strains in the nasal microbiome was observed.

Purpose: The SARS‐CoV‐2 pandemic has affected all countries in the world and is still ongoing. Although respiratory symptoms are the main manifestation of acute infection, there is also increasing evidence that neurological and vascular symptoms occur, and it is unknown whether residuals remain after patients have recovered. We therefore set out to investigate whether ocular vascular alterations remain after patients have recovered. Methods: Patients that had recovered from COVID‐19 infection within the last 6 months before inclusion and healthy age‐ and sex‐matched controls were recruited. Main inclusion criteria for patients were confirmed positive PCR test for SARS‐CoV‐2 in the medical history and positive testing for SARS‐CoV‐2 seroprevalence while controls had no history of COVID‐19 infection. Arteriovenous (AV) difference in oxygen saturation was calculated out of retinal arterial and venous oxygen saturation, which were measured with a commercially available Dynamic Vessel Analyser (DVA, Imedos, Germany). Retinal vessel diameters and arteriovenous ratio (AVR) were assessed using the same device. In addition, mean blur rate in the tissue area of the optic nerve head (MT) was quantified using laser speckle flowgraphy (LSFG, Nidek, Japan). Results: 29 patients that had recovered from moderate to severe COVID‐19 requiring hospitalization (mean age 35 ± 17 years) and 11 control subjects (mean age 36 ± 12 years) were included in the present study. No differences between groups regarding sex or concomitant diseases in the medical history were found. Body mass index (BMI) was significantly higher in patients that had recovered from COVID‐19 (27.5 ± 5.6 vs. 24.5 ± 2.8 m2/kg, p = 0.036). AVR as well as AV difference in oxygen saturation was significantly lower in patients compared to healthy controls (p = 0.021 for AVR and p = 0.023 for AV difference in oxygen saturation). MT in the optic nerve head also was significantly lower in patients (23.4 ± 10.1 a.u.) than in control subjects (47.3 ± 26.6 a.u., p < 0.001). Conclusions: The results of this study imply that retinal metabolism is still altered in patients after recovering from COVID‐19 infection. Longitudinal studies are required to investigate whether these changes in retinal vessels as well as optic nerve head blood flow are temporary or remain.