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J.H. K. Liu, R. Li, T.R. Nelson, R.N. Weinreb; Time–Dependent Change of Blood Velocity in the Rabbit Ophthalmic Artery . Invest. Ophthalmol. Vis. Sci. 2006;47(13):467.
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© ARVO (1962-2015); The Authors (2016-present)
To study change of blood velocity in the ophthalmic artery of light–dark entrained laboratory rabbit during the transition from the light phase to the dark phase.
Nine adult New Zealand albino rabbits were entrained to a daily 12–hour light and 12–hour dark cycle. In vivo blood velocity in the ophthalmic artery of the right eye was determined at –2 hr (baseline), 0 hr, 2 hr, and 4 hr after the onset of darkness. Pulsed and color Doppler images of the ophthalmic artery were captured using GE Logiq 9 ultrasound system with a 12 MHz linear transducer. Resistive index of blood flow was calculated using the peak systolic velocity and the end diastolic velocity. Measurements of intraocular pressure (IOP) were taken using a pneumatonometer at the same time points. An elevation of IOP was expected to occur due to the increase of ocular sympathetic activities during this light–dark transition time period. Repeated–measures ANOVA and post–hoc Bonferroni t–test were used to analyze data obtained from different time points. Measurements of blood velocity and IOP were taken again in the same rabbits after surgical decentralization of the ocular sympathetic nerves in the right eye.
Compared with the baseline, there was a significant increase of resistive index of blood flow at 2 hr and 4 hr after the onset of darkness. Elevations of IOP were also observed at the same time points. After sympathetic decentralization, the resistive indexes increased at all time points of –2 hr, 0 hr, 2 hr, and 4 hr from the pre–surgical values. There was also an increase of resistive index at 2 hr compared with the baseline value at –2 hr in the post–surgical rabbits. The IOP elevation during the transition of light–dark phases was significantly reduced due to the sympathetic decentralization as previously reported.
There was a time–dependent change of resistive index in the rabbit ophthalmic artery during the transition from the light phase to the dark phase. Ocular sympathetic activities can influence blood velocity in the ophthalmic artery. However, the increase of resistive index during the light–dark transition does not depend upon active ocular sympathetic activities.
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