Postural effects on spontaneous retinal venous pulsations in healthy individuals.
PURPOSE: To assess amplitudes of spontaneous retinal venous pulsations (SVP) in three various postures (sitting, supine and lateral decubitus) in healthy individuals. METHODS: Thirty participants (28 ± 8 years, 25 females) were included in the study. Intraocular pressure (IOP), blood pressure (BP) and SVP's were measured at three different postures using a calibrated Tono-Pen applanation tonometer, a digital sphygmomanometer, and a custom-built handheld video ophthalmoscope, respectively. Retinal venous pulsations (SVP) amplitudes were extracted from the retinal videos using a custom written MATLAB algorithm. Mean arterial pressure (MAP = (systolic + 2diastolic)/3) and mean ocular perfusion pressure (MOPP = (2/3 MAP)-IOP) were also calculated at each posture. A one-way ANOVA was applied to each parameter to determine any significant difference for the various postural changes. RESULTS: Mean IOP increased (p < 0.0001) and mean SVP decreased (p < 0.0001) from sitting to supine. The mean IOP (mmHg) and SVP (MU; measuring units) in sitting, supine and lateral decubitus were 16.2 ± 2, 19.4 ± 4, 19.8 ± 2 mmHg and 5.8 ± 2, 4.5 ± 2, and 4.7 ± 2 MU, respectively. Mean arterial pressure (MAP) and MOPP also decreased significantly from sitting to supine (p < 0.001, p < 0.001) and sitting to lateral decubitus (p < 0.05, p < 0.01). There were no significant differences between IOP, SVP, MAP or MOPP during a postural modification from supine to lateral decubitus. CONCLUSIONS: In this study, we showed a significant reduction in SVP amplitudes and a significant increase in IOP from sitting to supine position in a healthy young cohort. This supports the rationale to further study such phenomenon in ocular conditions such as glaucoma to determine whether relative SVP change, for a similar postural change, can reveal early signs of vascular dysfunction.
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