2.1 Cross-sectional Questionnaire
The most common methodology for assessment in the articles searched was a cross-sectional questionnaire which were conducted over a variety of mediums i.e. face to face, mobile application or web-based forms. The cohort of patients targeted also varied between inpatient and outpatient populations and in their geographical location (Tables 2 and 3). Whilst there are clear limitations to this approach and it is not possible to demonstrate a direct causal relationship between COVID-19 and OD but they are able to present associations in the symptomology of this pandemic.