Non-invasive Evaluation of Cerebrospinal Fluid Pressure in Ocular Hypertension: The Beijing Intracranial and Intraocular Pressure Study

Objective: To compare the orbital CSFP and trans-lamina cribrosa pressure difference (TLCPD) determined noninvasively in Ocular Hypertension (OH) and controls, and study its association with the estimated risk of conversion to glaucoma. Design: Cross-sectional observational study. Participants: 19 subjects with OH recruited from the Tongren Eye Center and 23 controls enrolled in the Beijing Intracranial and Intraocular Pressure Study between June 2010 to December 2013. Methods: Magnetic resonance imaging was used to measure orbital subarachnoid space width (OSASW) at 3, 9 and 15 mm posterior to the globe. The CSFP (mmHg) was estimated from a published formula as 17.54 × MRI derived OSASW at 15 mm behind the globe +0.47 × body mass index +0.13 × mean arterial blood pressure -21.52. Estimated TLCPD was calculated as IOP- CSFP. The values of CSFP and TLCPD were compared between OH and controls. The estimated risk of progression to glaucoma in OH was calculated and its correlation with CSFP determined. Main outcome measures: Orbital subarachnoid space width; MRI derived CSFP value; TLCPD value. Association of risk of progression with CSFP. Results: The orbital subarachnoid space width was significantly wider (P=0.01) in the OH group than in the control groups at all three measurement locations. The MRI derived CSFP value in OH (14.9 ± 2.9 mmHg) was significantly higher than in the normal group (12.0 ± 2.8 mmHg; P<0.01). The estimated TLCPD value in OH (9.0 ± 4.2 mmHg) was significantly higher than in controls (3.6 ± 3.0 mmHg; P<0.01). The estimated risk of conversion to glaucoma in OH (15.2 ± 8.7%) was negatively correlated with the MRI derived CSFP value (r=-0.51, r2=-0.26, P<0.01). Conclusions: The wider OSASW and higher estimated CSFP in OH subjects suggest a higher orbital CSFP. Despite a higher orbital CSFP that could be protective, the higher TLCPD in OH may play a significant role in the risk of developing glaucoma.