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Hiroki Mieno, Kentaro Kojima, Kazuhito Yoneda, Kenji Nagata, Tohru Inaba, Yoshinori Marunaka, Chie Sotozono; Measurement and analysis of pH in human vitreous body. Invest. Ophthalmol. Vis. Sci. 2018;59(9):336. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
There have been no previous reports on the pH of the human vitreous body, yet it has been suggested that the vitreous pH possibly changes due to diabetes. In this study, we report our new method for measuring the pH of the human vitreous body and our investigation into whether or not there is a difference depending on the presence of diabetes.
This study involved 37 patients with no previous history of ophthalmologic surgery who underwent vitreous surgery at the Department of Ophthalmology, Kyoto Prefectural University of Medicine Hospital, Kyoto, Japan from February to October 2017. There were 12 cases with diabetes mellitus (DM) (DM+ Group) and 25 cases without DM (DM- Group). Vitreous pH was measured by use of the ABL 800 FLEX blood gas analyzer (Radiometer Medical ApS, Copenhagen, Denmark) as soon as possible after being anaerobically collected via 27-gauge vitreous surgery. Venous blood collected immediately before surgery was measured via the same method. Comparison of pH between the two groups and correlation between pH, patient age, and body mass index (BMI) were analyzed.
In the DM+ Group and the DM- Group, the mean±standard deviation (95% confidence interval of the mean) vitreous pH was 7.25±0.03 (7.23-7.28) and 7.25±0.02 (7.24-7.26), respectively, and that of venous blood pH was 7.39±0.04 (7.37-7.42) and 7.40±0.02 (7.39-7.41), respectively. No significant difference in vitreous pH and venous blood pH was found between the two groups. As a result of a total of 37 cases, the Pearson correlation coefficient between the vitreous pH and the venous blood pH was 0.443 (p=0.007). However, neither pH was correlated with patient age and BMI.
No change in pH was observed in both vitreous and venous blood, regardless of the presence or absence of diabetes. As has been known so far, the venous blood pH moves within the narrow range of 7.35-7.45, and the vitreous pH also moves within a narrow range. We speculate that the vitreous body, as well as blood, has high buffering capacity.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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