The effect of body position on intraocular and CSF pressures in the lateral ventricle, and in cortical and lumbar subarachnoid spaces in cats.
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).


CONCLUSIONS
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.
Department of Ophthalmology, University of Zagreb School of Medicine, Zagreb, Croatia.
Tomislav
T
Kuzman
Ivana
I
Jurjević
Inga
I
Mandac
Milan
M
Radoš
Darko
D
Orešković
Hrvoje
H
Jednačak
Marijan
M
Klarica
D000818:Animals; D002415:Cats; D015170:Cerebrospinal Fluid Pressure / Q000502:physiology*; D005260:Female; D007429:Intraocular Pressure / Q000502:physiology*; D020547:Lateral Ventricles / Q000502:physiology*; D008297:Male; D011187:Posture; D013346:Subarachnoid Space / Q000502:physiology