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S. Oono, T. Kurimoto, H. Oku, Y. Tagami, N. Okamoto, T. Ikeda, O. Mimura; Effect of Transcorneal Electrical Stimulation on Chorioretinal Blood Flow in Normal Human Subjects. Invest. Ophthalmol. Vis. Sci. 2009;50(13):412.
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Transcorneal electrical stimulation (TcES) activates the retina and can improve the visual function of patients with retinal artery occlusions (RAOs; Koichi et al., Graefe’s Arch Exp Ophthalmol 2007). TcES can also activate the trigeminal nerve which leads to a vasodilation of the middle cerebral artery. This then increases the cerebral blood flow in adult rats (Atalay B et al., J Neurosurg, 2002). However, it has not been determined whether TcES increases the ocular blood flow. Thus, the purpose of this study was to determine whether TcES increases the chorioretinal blood flow in normal human subjects.
The chorioretinal blood flow of 10 healthy men volunteers without any systemic or ophthalmic diseases was measured. The ages of subjects ranged from 26 to 37 years. Laser speckle flowgraphy (LSFG) with a square blur rate (SBR) was used to measure the chorioretinal blood flow immediately after and 3, 24, and 40 hrs after the TcES. The standard ratio of the SBR of the stimulated eye was compared to that of the fellow eye (Tamaki et al., Exp Eye Res, 1995). The control eyes had the contact lens electrode placed on the cornea but electrical stimulation was not given. At all measurement times, the intraocular pressure (IOP) in both eyes, pulse rate, systemic blood pressures, and the ocular perfusion volume were measured.
SBR increased immediately after beginning the TcES. The standard ratio of the SBR peaked at 24 hrs and then gradually decreased. The mean standard ratio in the TcES group at 24 hrs was 1.24 (n=6) which was significantly higher than the 0.98 (n=4) in the control group (P <0.005). The differences in the IOPs, pulse rates, blood pressure, and perfusion volumes in the two eyes were not significant.
These results showed that a single TcES session can increase the chorioretinal blood flow for a relatively long period in normal human subjects. This increase of ocular blood flow may have contributed to the visual field improvement following TcES in the patient with RAOs.
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