COVID-19 can cause blink reflex abnormalities.

Background and purpose: Neurological symptoms and complications associated with coronavirus 2019 (COVID-19) are well known. It was aimed to evaluate the brainstem and trigeminal/facial nerves and the pathways between these structures in COVID-19 using the blink reflex test. Methods: Thirty patients with post COVID-19 (16 males, 14 females) and 30 healthy individuals (17 males, 13 females) were included in this prospective study. Individuals who previously had a positive nose swap polymerase chain reaction test for severe acute respiratory syndrome coronavirus 2 and whose previously clinical features were compatible with COVID-19 were included in the post COVID-19 patient group. Neurological examination of the participants should be normal. Blink reflex test was performed on all participants. R1, ipsilateral R2 (IR2), and contralateral R2 (CR2) waves obtained from the test were analyzed. Results: The mean ages of healthy individuals and post COVID-19 patients were 34.0±6.4 and 38.4±10.6 years, respectively. Both age and gender were matched between the groups. R1, IR2, and CR2 latencies/amplitudes were not different between the two groups. The side-to-side R1 latency difference was 0.5±0.3 and 1.0±0.8 ms in healthy individuals and post COVID-19 patients, respectively (p=0.011). One healthy individual and 12 patients with post COVID-19 had at least one abnormal blink reflex parameter (p=0.001). Conclusion: This study showed that COVID-19 may cause subclinical abnormalities in the blink reflex, which includes the trigeminal nerve, the seventh nerve, the brainstem, and pathways between these structures.

Eye Movement Alterations in Post-COVID-19 Condition: A Proof-of-Concept Study.

There is much evidence pointing out eye movement alterations in several neurological diseases. To the best of our knowledge, this is the first video-oculography study describing potential alterations of eye movements in the post-COVID-19 condition. Visually guided saccades, memory-guided saccades, and antisaccades in horizontal axis were measured. In all visual tests, the stimulus was deployed with a gap condition. The duration of the test was between 5 and 7 min per participant. A group of n=9 patients with the post-COVID-19 condition was included in this study. Values were compared with a group (n=9) of healthy volunteers whom the SARS-CoV-2 virus had not infected. Features such as centripetal and centrifugal latencies, success rates in memory saccades, antisaccades, and blinks were computed. We found that patients with the post-COVID-19 condition had eye movement alterations mainly in centripetal latency in visually guided saccades, the success rate in memory-guided saccade test, latency in antisaccades, and its standard deviation, which suggests the involvement of frontoparietal networks. Further work is required to understand these eye movements' alterations and their functional consequences.

Evaluation of VDT-Induced Visual Fatigue by Automatic Detection of Blink Features.

This study evaluates the progression of visual fatigue induced by visual display terminal (VDT) using automatically detected blink features. A total of 23 subjects were recruited to participate in a VDT task, during which they were required to watch a 120-min video on a laptop and answer a questionnaire every 30 min. Face video recordings were captured by a camera. The blinking and incomplete blinking images were recognized by automatic detection of the parameters of the eyes. Then, the blink features were extracted including blink number (BN), mean blink interval (Mean_BI), mean blink duration (Mean_BD), group blink number (GBN), mean group blink interval (Mean_GBI), incomplete blink number (IBN), and mean incomplete blink interval (Mean_IBI). The results showed that BN and GBN increased significantly, and that Mean_BI and Mean_GBI decreased significantly over time. Mean_BD and Mean_IBI increased and IBN decreased significantly only in the last 30 min. The blink features automatically detected in this study can be used to evaluate the progression of visual fatigue.