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W.-C. Liu, M. C. Lin; Effect of Eye-Rubbing and Breath-Holding on Corneal Biomechanical Properties and Intraocular Pressure. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1757.
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Previous studies found that frequent eye-rubbing plays a role in the pathogenesis of keratoconus. Recent studies also reported that corneal hysteresis (CH) and corneal resistance factor (CRF) are significantly lower in keratoconic eyes than in normal eyes. The purpose of the eye-rubbing test is to investigate the effect of eye-rubbing on CH and CRF. It is a common observation for patients to hold their breath during a particular eye examination, especially when they are nervous. Simple breath-holding may lead to a transient increase in intraocular pressure (IOP). The purpose of the breath-holding test is to investigate the effect of breath-holding on IOP.
32 subjects were recruited. For every subject, one eye was randomly selected for an eye-rubbing test; the other eye was for a breath-holding test. The eye-rubbing test included two episodes, each lasting 20 sec. with a 2-min. break in between. Ocular Response Analyzer (ORA) was used to measure corneal biomechanical properties and compared the results from: (1) Before eye-rubbing (Baseline); (2) Immediately after the first episode of eye-rubbing (ER1); (3) Immediately after the second episode of eye-rubbing (ER2). The breath-holding test also included two episodes. At the first episode, the subject was asked to breathe normally then hold the breath. At the second episode, the subject was asked to take a deep breath then hold the breath. ORA was used to measure IOP and compare the results from: (1) Before breath-holding (Baseline); (2) During the first episode of breath-holding (BH1); (3) During the second episode of breath-holding (BH2).
In the eye-rubbing test, compared with mean baseline measurement, both biomechanical parameters significantly decreased after ER1 (P<0.05, paired t test) and after ER2 (P<0.05, paired t test). In addition, the corneal biomechanical values obtained from ER2 were significantly decreased when compared with the values obtained from ER1 (P<0.05, paired t test). In the breath-holding test, there was no significant difference with Goldmann correlated IOP and corneal compensated IOP between the baseline, BH1 and BH2.
In the eye-rubbing test, both biomechanical parameters were significantly decreased after eye-rubbing episodes. There is suggestion of accumulative effect from repetitive eye-rubbing. In the breath-holding test, there was no significant change in IOP values regardless of whether the subject took a deep breath during measurement.
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