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Abstract #48269 Published in IGR 13-4
Diurnal pattern of intraocular pressure is affected by microgravity when measured in space with the pressure phosphene tonometer (PPT)
Chung KY; Woo SJ; Yi S; Choi GH; Ahn CH; Hur GC; Lim JG; Kim TWJournal of Glaucoma 2011; 20: 488-491
See also comment(s) by Marco Vizzeri •
PURPOSE: This study was designed to evaluate the effect of microgravity on the diurnal variation of intraocular pressure (IOP). METHODS: IOPs were measured with the pressure phosphene tonometer in 1 subject (the first Korean astronaut) during spaceflight. IOPs were measured every 3 hours during day time (6 times per day) at 2 separate days in space with 3 repeated measurements at each time on both eyes. A total of 72 measurements were obtained during spaceflight. To obtain control IOP data, IOP was measured using the same protocol on ground before spaceflight. RESULTS: Mean IOP increased by 26.3% during spaceflight compared with that on ground [16.47 ± 0.60 (SD) mm Hg vs. 13.04 ± 0.74 mm Hg, P<0.001). The IOP elevation was maintained until Launch+8 days. There was no significant difference in IOP increase between right and left eyes (16.4 2 ± 0.65 mm Hg right eye vs. 16.53 ± 0.56 mm Hg left eye). There was a different pattern of diurnal variation of IOP during spaceflight compared with that on ground. The IOP at 7 AM was the lowest under microgravity, whereas it was the highest on ground. The slope of the best fit line for diurnal IOP measures was 0.0349 mm Hg/h (95% confidence interval: 0.0082-0.0616) under microgravity and -0.0294 mm Hg/h (95% confidence interval: -0.0063-0.0041) on ground. CONCLUSIONS: The study showed a different diurnal pattern of IOP under microgravity compared with that on ground. This result suggests that gravity and subsequent body fluid shift is one of the determining factors of IOP diurnal variation.
School of Military Medicine, AFMC, Daejeon, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam, Korea. spacechung@hotmail.com
Classification:
6.1.2 Fluctuation, circadian rhythms (Part of: 6 Clinical examination methods > 6.1 Intraocular pressure measurement; factors affecting IOP)
6.1.3 Factors affecting IOP (Part of: 6 Clinical examination methods > 6.1 Intraocular pressure measurement; factors affecting IOP)