Changes in Retinal Hemodynamics in the Optic Nerve Head of Healthy Participants Measured Using Laser Speckle Flowgraphy after a Cold Pressor Test.

PURPOSE: Autoregulation of retinal vessels is stronger than that of choroidal vessels. This study aimed to use laser speckle flowgraphy to determine the time course of changes in retinal hemodynamics of healthy eyes after a cold pressor test. METHODS: This prospective study included 44 right eyes of 44 healthy volunteers (age, 21.7 ± 5.0 years). The mean blur rate, which is a quantitative index of the relative blood flow velocity in the retina, was measured using laser speckle flowgraphy. The vessel average of mean blur rate at the optic nerve head, intraocular pressure, systolic blood pressure, diastolic blood pressure, mean blood pressure, heart rate, and ocular perfusion pressure were evaluated at baseline, immediately after the cold pressor test, and 10, 20, and 30 minutes after the test. RESULTS: Immediately after the test (0 minutes), systolic blood pressure, diastolic blood pressure, mean blood pressure, and ocular perfusion pressure were significantly increased compared with those at baseline; however, no changes were observed at 10, 20, and 30 minutes after the test. In contrast, intraocular pressure, heart rate, and the vascular mean blur rate values at the optic nerve head did not change throughout the course of the study. CONCLUSIONS: Sympathetic hyperactivity induced by the cold pressor test increased systemic circulatory dynamics, but not retinal circulatory hemodynamics, suggesting the involvement of vascular autoregulation.

Choroidal Thickness Increases During Parasympathetic Dominance After Immersion of the Foot in Warm Water.

PURPOSE: This study aimed to assess the course of changes in choroidal morphology after immersion of the foot in warm water at 40°C using enhanced depth imaging optical coherence tomography (EDI-OCT). METHODS: Forty-three right eyes of 43 healthy participants were included. Changes in choroidal morphology were determined using EDI-OCT to evaluate subfoveal choroidal thickness (SCT). Systolic, diastolic, and mean blood pressures (SBP, DBP, and MBP, respectively) were also measured to determine systemic circulatory dynamics at baseline, immediately after immersion (0 min), and 10, 20, and 30 min after immersion. RESULTS: Immediately after immersion, SBP, DBP, and MBP were significantly declined versus baseline. In contrast, the SCT was significantly increased after warm water immersion. However, all these parameters did not change significantly compared to the baseline within 30 min. CONCLUSION: In the normal eye, parasympathetic nerve activity induced by warming stimuli increases choroidal morphology in response to a decrease in systemic circulatory activity, which normalizes within 30 min. The findings of this study may provide basic data for the prevention and treatment of various choroidal diseases in which sympathetic hyperactivity is involved in the pathogenesis.

Descending Necrotizing Mediastinitis Caused by Streptococcus pyogenes in a Child with Primary Epstein-Barr Virus Infection.

Descending necrotizing mediastinitis (DNM) is a severe, life-threatening disease with a high mortality rate resulting from sepsis or other complications. DNM can also be a rare and severe complication of Epstein-Barr virus (EBV) infection in adolescents and young adults but has never been reported in a pre-school child. A 4-year-old girl was admitted to our hospital with a 2-day history of fever and chest pain. Computed tomography (CT) revealed a right sided pleural effusion, fluid collection in the retropharyngeal and mediastinal areas, cervical lymphadenopathy, and marked hepatosplenomegaly. She was diagnosed with empyema, retropharyngeal abscess, and mediastinitis. To improve her dyspnea, a chest tube was inserted, and antibiotic treatment was initiated. Her condition improved temporarily, but on day 5 in our hospital, she developed a fever again. A repeat CT scan showed exacerbation of fluid retention in the retropharyngeal area and the mediastinum, for which she underwent drainage and debridement of necrotic tissue in the retropharynx and mediastinum. The presence of cervical lymphadenopathy and marked hepatosplenomegaly suggested the involvement of EBV. Serological tests for EBV revealed primary EBV infection at the time of the DNM onset. Finally, she was diagnosed with DNM following primary EBV infection. At follow-up 1 year later, she was doing well. The risk of DNM should be recognized in patients, even pre-school aged children, with primary EBV infection.

The effect of thermal history on the elasticity of K-type gellan gels.

Elasticity of potassium type gellan gels prepared at different thermal histories was examined using dynamic viscoelastic measurements. The storage Young's modulus E' decreased with increasing cooling rate during gelation. Once gel formation occurred, thermal history at lower temperature did not influence the elastic modulus and thermal stability of the gellan gels. On the other hand, thermal history around gelation temperature influenced strongly the elastic modulus and thermal stability of resulting gels. When the gellan solution was kept for a certain time before cooling at a temperature near the gelation temperature, it was found that gels with higher elastic modulus and thermal stability were formed.