Background It is crucial that world leaders mount effective public health measures in response to COVID-19. Twitter may represent a powerful tool to help achieve this. Here, we explore the role of Twitter as used by Group of Seven (G7) world leaders in response to COVID-19. Methods This was a qualitative study with content analysis. Inclusion criteria were as follows: viral tweets from G7 world leaders, attracting a minimum of 500 ‘likes’; keywords ‘COVID-19’ or ‘coronavirus’; search dates 17 November 2019 to 17 March 2020. We performed content analysis to categorize tweets into appropriate themes and analyzed associated Twitter data. Results Eight out of nine (88.9%) G7 world leaders had verified and active Twitter accounts, with a total following of 85.7 million users. Out of a total 203 viral tweets, 166 (82.8%) were classified as ‘Informative’, of which 48 (28.6%) had weblinks to government-based sources, while 19 (9.4%) were ‘Morale-boosting’ and 14 (6.9%) were ‘Political’. Numbers of followers and viral tweets were not strictly related. Conclusions Twitter may represent a powerful tool for world leaders to rapidly communicate public health information with citizens. We would urge general caution when using Twitter for health information, with a preference for tweets containing official government-based information sources.

Purpose: To evaluate structural grading and quantitative segmentation of foveal hypoplasia using handheld OCT, versus preferential looking (PL), as predictors of future vision in preverbal children with infantile nystagmus.Design: Longitudinal cohort study.Participants: Forty-two patients with infantile nystagmus (19 with albinism, 17 with idiopathic infantile nystagmus, and 6 with achromatopsia) were examined.Methods: Spectral-domain handheld OCT was performed in preverbal children up to 36 months of age. Foveal tomograms were graded using our 6-point grading system for foveal hypoplasia and were segmented for quantitative analysis: photoreceptor length, outer segment (OS) length, and foveal developmental index (FDI; a ratio of inner layers versus total foveal thickness). Patients were followed up until they could perform chart visual acuity (VA) testing. Data were analyzed using linear mixed regression models. Visual acuity predicted by foveal grading was compared with prediction by PL, the current gold standard for visual assessment in infants and young children.Main Outcome Measures: Grade of foveal hypoplasia, quantitative parameters (photoreceptor length, OS length, FDI), and PL VA were obtained in preverbal children for comparison with future chart VA outcomes.Results: We imaged 81 eyes from 42 patients with infantile nystagmus of mean age 19.8 months (range, 0.9e33.4 months; standard deviation [SD], 9.4 months) at the first handheld OCT scan. Mean follow-up was 44.1 months (range, 18.4e63.2 months; SD, 12.0 months). Structural grading was the strongest predictor of future VA