Background: Correlation between cerebrospinal fluid (CSF) and intraocular pressure (IOP) is still unclear. We compared CSF pressure from different parts of the CSF system and IOP measured by the same invasive technique in a new experimental model in cats during changes of body position.
Methods: Pressure changes were recorded on anesthetized cats (n = 7) in the lateral ventricle (LV), in the cortical (CSS) and lumbar (LSS) subarachnoid spaces, and in the anterior ocular chamber. Animals and measuring instruments were both fixed on a board at an adequate hydrostatic level.
Results: In a horizontal position, IOP (18.5 ± 0.6 cm H(2)O) and CSF pressures (LV = 17.4 ± 0.9; CSS = 17.2 ± 0.7; LSS = 17.8 ± 1.2 cm H(2)O) were similar. In a vertical position, pressure in the LSS increased (33.5 ± 2.3 cm H(2)O), pressures inside the cranial cavity dropped (LV = -4.1 ± 0.9 cm H(2)O; CSS = -4.8 ± 0.5 cm H(2)O), while IOP slightly decreased (14.3 ± 0.1 cm H(2)O).
Conclusion: Change in body position from horizontal to upright causes drastic changes in CSF pressure and relatively small changes in IOP, which indicates that the IOP does not reflect CSF pressure. In an upright position, CSF pressures were equal at the same hydrostatic level in LV and CSS, which suggests that CSF pressure inside the cranium depends on its anatomical and biophysical features, and not on CSF secretion and absorption.