Postural effects on blood pressure, intraocular pressure, and ocular perfusion pressure in patients with spinal cord injury.

BACKGROUND: Reduced ocular perfusion pressure (OPP) from hypotension and consistent OPP variability due to blood pressure (BP) fluctuations are predisposing factors for glaucoma. Low resting BP and orthostatic hypotension (OH) in spinal cord injury (SCI) patients may increase the risk of glaucoma post-injury. This study investigated BP, intraocular pressure (IOP), and OPP changes between supine and sitting positions in SCI and normal individuals.

METHODS: Twenty SCI cases (high paraplegia, T1-T6 n  = 6; low paraplegia, T7-L3 n  = 14) and matched controls (1:1) were included. Systolic and diastolic BP (SBP and DBP) were measured digitally, and IOP with rebound tonometry. Measurements were taken one minute apart in both positions. Mean arterial pressure (MAP) was calculated, and OPP was determined using position-specific formulas.

RESULTS: No SCI subjects exhibited OH. Both groups experienced significant BP increment ( P  < 0.05) from supine to sitting. SBP increased by 4.4 ± 8.4 mmHg (SCI) and 3.6 ± 6.2 mmHg (normal), while DBP increased by 4.2 ± 5.1 mmHg (SCI) and 6.7 ± 5.5 mmHg (normal). IOP and OPP decreased significantly ( P  < 0.05) after postural change in both groups, yet differences between them were not significant. Analysis by injury level revealed lower parameter values in high paraplegia than in low paraplegia, with the latter group showing a more significant reduction in OPP after postural change.

CONCLUSION: Postural changes differently affect BP, IOP, and OPP in SCI compared to normal individuals, with variations based on the level of SCI. While not directly assessing glaucoma, the study offers insights into ocular hemodynamics in SCI compared to normals.