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J. Takayama, A. Tomidokoro, M. Nagahara, A. Mishima, M. Araie; Time-Courses of Circulation Change in Human Optic Nerve Head and Retina After Topical Installation of Phenylephrine Evaluated With Laser Speckle and Laser Doppler Methods . Invest. Ophthalmol. Vis. Sci. 2003;44(13):123.
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Purpose: To study the time-course of changes in circulation in human optic nerve head (ONH) and retina after topical instillation of 5% phenylephrine using two different noninvasive methods each. Methods: In normal human volunteers, 20 µl of 5% phenylephrine hydrochloride into one randomly chosen eye and physiological saline into the other eye were applied three times at 15-min intervals. The normalized blur value in the ONH (NBonh), a quantitative index of ONH blood velocity obtained by the laser speckle method, and resistance index (RI) of a major retinal artery calculated using retinal blood flow velocities obtained by the laser Doppler velocimetry (CLBF model 100, Canon) were determined at 45-min intervals for 180 min. Intraocular pressure, arterial blood pressure, and pulse rate were also monitored. All measurements were carried out in a double-blinded manner. Results: NBonh significantly decreased to 95.6 [1.0]% (mean [SEM], N=11), 89.3 [3.7]%, 87.0 [3.7]%, and 89.8 [3.2]% compared to the baseline at 45, 90, and 135 min after instillation, respectively. RI significantly increased to 108.6 [5.4]% at 90 min and returned to the baseline level at 180 min. NBonh and RI in the saline-treated control eyes showed no significant change. Bilateral difference was significant both in NBonh (ANOVA, P0.001) and RI (P=0.003). Bilateral difference was significant at 45 (P=0.020), 90 (P=0.007) and 135 min (P=0.006) in NBonh and at 90 min (P=0.024) in RI, respectively. Intraocular pressure in the both eyes, arterial blood pressure, and pulse rate showed no significant changes. Conclusions: Topical phenylephrine caused a small, but significant decrease in blood velocity in the ONH and increase in resistance index in the retinal artery in normal humans only in the ipsilateral eye, suggesting direct effect of phenylephrine locally penetrating and possible unfavorable effects of this drug on circulation in the posterior segments of the eye.
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