Changes in the vitreous body after experimental vitreous hemorrhage in rabbit: An interdisciplinary study.

PURPOSE: To explore the changes in vitreous body after vitreous hemorrhage and assess its prognosis from the perspective of vitreoretinal interface. METHODS: The experiment was performed on 32 New Zealand rabbits (64 eyes), weighing 2500-3000 g for 4 months and unlimited gender, which was injected with 0.2 mL of autologous blood into the center of vitreous cavity-the study group (right eyes), and the control one was treated in the same manner with equal volumes of saline. The rabbits were randomly and equally divided into the following four batches according to the days of observation: Days 3, 7, 14, and 30 after injection. IOP and severity grading were evaluated before rabbits' execution and eyeballs were enucleated. The anterior segment was separated to flow out the vitreous body naturally to detect the liquefaction degree and viscosity. Then, chemical composition of electrolytes, PCT and bFGF were determined by colorimetry and enzyme-linked immunosorbent assay (ELISA). Finally, the incidence of posterior vitreous detachment (PVD) was observed after vitreous sampled. The studies were double-blind. RESULTS: After injection, the extent of vitreous opacity and coagulum size decreased over time. Both the degree of liquefaction and the length of tow differed significantly between two groups at different time points (all p < 0.001). The liquefaction degree in the study group rose obviously from the Day 14, which the viscosity declined significantly on the initial time. Biochemical markers fluctuated temporarily, except for basic fibroblast growth factor (bFGF), which continued to rise and was correlated with the liquefaction degree (r = 0.658, p < 0.001). Besides, the incidence of PVD increased from the 14th day (p < 0.05), and it was highly positively correlated with the number of macrophages (r = 0.934; p < 0.001). CONCLUSION: After vitreous hemorrhage, the changes of the vitreous body are relatively minor earlier (2-4 weeks), but irreversible later. Specifically, the degree of liquefaction increases with a decrease in viscosity, and the chemotaxis of macrophages and bFGF induce incomplete PVD.

The influence of COVID-19 lockdowns on presentation with spontaneous posterior vitreous detachment to the emergency department in Italy.

The purpose of the study was to analyze the frequency of the spontaneous posterior vitreous detachment (PVD) in patients admitted to an Emergency Eye Department in Italy (EED) during the COVID-19 pandemic national lockdown in 2020 compared with the similar time period in 2019. In this retrospective observational study, patient records for ophthalmology EED patients in the month of April 2020 during the COVID-19 Italian national lockdown, were compared with those for an equivalent one-month period in 2019. Diagnoses, gender, and age were assessed. Unpaired Student t-tests were used for continuous variables. Poisson regression was used for count analysis to compare categorical variables. Chi-square test was applied to asses proportion differences. In comparison with the 2019 equivalent period, there was a significant decrease in the overall number of EED visits and in the number of patients presenting with a spontaneous PVD during the 2020 lockdown (-41.6% and -49%, respectively). During the 2020 lockdown, all diagnostic categories showed less patient admittance, however, the proportions remained stable when considering the entire cohort. The proportion of urgent visits was 90% in 2020 and 86% in 2019 (p = 0.66). The proportion of EED patients affected by spontaneous PVD was comparable between the two study periods (8.4% in 2020 vs. 9.6% in 2019, p = 0.34). Patients presenting with spontaneous PVD in both periods were significantly older when compared to patients with other pathologies (mean age of 63years in 2020 and 64years in 2019, p < 0.001). There was a significant bias in female gender (61.2% in 2019 and 60% in 2020, p < 0.05). There was a significant decrease of accesses to the EED during COVID-19 2020 lockdown. Patients affected by spontaneous PVD were about 50% less compared with the same period of 2019. Risk factors for the development of spontaneous PVD were older age and female gender. PVD represents a potentially visual function threatening condition because it can cause retinal ruptures and retinal detachment. Patients need to be educated to get urgent ophthalmic assessments in the presence of important acute signs and symptoms, like floaters and flashes, even in the presence of a lockdown.