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P. Sauvageau, C. Boisjoly, J. Morin, V. Diaconu; Retinal Flicker Stimulation Affects the Cardiac Rhythm. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2270.
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Previous studies proposed that flicker retinal excitation increases the neuronal metabolism of the eye and could influence parameters of the retinal vascular system. Falsini et al.(2002) suggested a relation between the retinal neural activity and the contractions of the retinal vessels. Riva et al.(2004) observed an increase in blood flow in the human optic nerve head (ONH) after a flicker retinal stimulation. On the other hand, flicker retinal stimulation affects inevitably the visual cerebral cortex and its related regions. The purpose of the present study was to determine the brain involvement in the regularization of the retinal blood flow in relation with a flicker retinal excitation.
An intermittent flicker excitation was applied to an eye. The human optic nerve head (ONH) capillaries were examined in the controlateral eye with the full spectrum reflectometry measurement technique. The relative oxyhemoglobin, hemoglobin and capillary blood contents in the contralateral eye were obtained from this.The full spectrum reflectometry measurements were performed with a version of the "On line Spectroreflectometry Oxygenation Measurement in the Eye" instrument (OSOME Faubert & Diaconu US Patent # 5,919,132). The 15 Hz flicker excitation was produced by a stroboscopic lamp, representing 300 visual angle uniform diffused green (540nm) light of 60cd/m2 maximal intensity.Thirteen volunteers between the age of 19 and 54 years old, with normal eye examination, participated in this experiment.An experimental session consisted in recording on line the full spectrum reflection from the ONH of the right eye of each subject for a period of 240 seconds. During the recording, flicker excitation was applied to the left eye for two periods of 60 seconds, interspersed by 60 second intervals. Using a finger pulse oxy-meter, the subject cardiac rhythm was recorded for the duration of the entire experiment period.
The results demonstrated that flicker affects not only the blood oxygenation in the contralateral eye ONH but also the cardiac rhythm of the subjects. It is also important to notice that the variations of both the blood oxygenation and the cardiac rhythm were in countered phase. When the blood oxygenation decreased, the cardiac rhythm increased.
The results of the present study suggested that it is difficult to isolate the retinal flicker stimulation from the cortex stimulation. The cardiac rhythm should be one of the parameters to be considered when evaluating the retinal blood flow parameters.
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