Background Non-arteritic ischaemic optic neuropathy (NAION) is a rare but harmful complication of prone positioning. Prone mechanical ventilation is a therapeutic strategy which has been used extensively during the COVID-19 pandemic to treat acutely hypoxemic patients with COVID-19 related acute respiratory distress syndrome (ARDS). Though a small number of cases of unilateral NAION have been reported in patients testing positive for the SARS-CoV-2 virus, we describe what is to our knowledge, the first reported case of bilateral NAION occurring in a patient proned extensively for the treatment of COVID-19 related ARDS. We consider the potential aetiological factors leading to NAION after prone mechanical ventilation in patients with COVID-19 and suggest strategies to protect against its development. Case presentation : We report a case of severe, irreversible, visual impairment secondary to bilateral anterior ION in a fifty-five-year-old male who underwent eight episodes of prone mechanical ventilation to treat COVID-19 related ARDS. Once weaned from his sedation he reported bilateral painless vision loss, and bedside ophthalmological assessment identified a reduced visual acuity of 3/30 unaided in the left eye and counting fingers in the right. Dilated indirect ophthalmoscopy revealed inferotemporal optic disc oedema with splinter haemorrhages in the right eye and mild disc oedema, temporal pallor, and nerve fibre layer haemorrhages inferiorly in the left eye. Humphrey visual field 24 − 2 testing confirmed a severely constricted visual field with macular sparing on the right and depressed inferonasal vision with preserved peripheral vision on the left eye. OCT disc imaging shortly after diagnosis revealed bilateral disc swelling and flame haemorrhages in the right eye. Conclusions NAION is a devastating, but preventable complication of prone positioning, which may pose significant risk of vision loss in patients with COVID-19 related ARDS.

Abstract. MNISIKLIS is an integrated system aiming to provide universal, indoor location-based services focusing on navigation. This paper presents the overall MNISIKLIS architecture and certain implementation details. In the context of the Design for All approach, the system targets to the support of several types of users, including persons with disabilities as well as elderly, by exploiting multimodal interaction. Moreover, the system implements efficient path finding algorithms and provides advanced user experience through highly personalized services. MNISIKLIS adopts Semantic Web technologies (e.g., ontologies and reasoning methods) for representing and managing application models. Furthermore, MNISIKLIS exploits modern positioning techniques in order to achieve high quality positioning. The paper discusses the algorithms and the models that accommodate the services provided by the system. Additionally, an analysis of the positioning subsystem, the user interaction subsystem and the peripheral infrastructure is given. Hence, a new paradigm in the area of location-based systems is presented.