The Japanese Journal of Physiology
Print ISSN : 0021-521X
Regular Papers
Measurement of Intraocular Pressure by Both Invasive and Noninvasive Techniques in Rabbits Exposed to Head-Down Tilt
Akira SETOGAWAYasuaki KAWAI
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1998 Volume 48 Issue 1 Pages 25-31

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Abstract
This study investigates changes in intraocular pressure (IOP) in rabbits during head-down tilt (HDT), which is commonly used as an experimental model to simulate microgravity. IOP was measured by the needle insertion technique (IOPNEEDLE) and Tono-pen tonometry (IOPTONO-PEN). Although the absolute value of the IOPTONO-PEN was significantly smaller than that of the IOPNEEDLE, a significant correlation (r=0.99) was observed between them. A linear regression analysis yielded an equation as follows: IOPTONO-PEN=0.67 IOPNEEDLE−0.67. Both the IOPNEEDLE and the IOPTONO-PEN changed depending on the tilt angle. Tilting from horizontal (0°) to 75° head-down increased the IOPNEEDLE and the IOPTONO-PEN by 7.3±0.8 (mean±SEM) mmHg and 4.4±1.3mmHg. The IOPNEEDLE elevated from 13.1±1.3 to 16.9±1.0mmHg immediately after the onset of 45° HDT and then gradually declined. The value of the IOPNEEDLE during 8h of HDT was significantly higher than the value in the control animals, which were kept at the horizontal prone position throughout the experiment. Similar findings were observed in the IOPTONO-PEN. These results suggest that the needle insertion technique and the Tono-pen tonometry are both useful for measuring IOP in rabbits.
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© 1998 by The Physiological Society of Japan
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