Investigation of factors influencing intracranial pressure (ICP), as well as pulsations in both ICP and intraocular pressure (IOP), in glaucomatous and normal subjects.

Abstract

Purpose : To investigate the influence of several factors on intracranial pressure (ICP), pulsations in ICP, and ocular pulse amplitude (OPA), in subjects with and without glaucomatous damage.

Methods : Right eyes of 86 prospectively enrolled subjects were studied to investigate ICP in primary open angle glaucoma (POAG: n = 28), normal tension glaucoma (NTG: n = 12), ocular hypertension (OHT; n = 7), and normal subjects (NRM: n = 39). IOP and OPA were measured with PASCAL Dynamic Contour Tonometry (DCT) and Model 30 Pneumatonometry (PNT), acquired sitting (sit), and for PNT, also supine (sup) and lateral decubitus during (dur) a lumbar puncture. Cerebrospinal fluid pressure (CSFP), a surrogate for ICP, was measured using an electronic transducer with a 27 gauge spinal needle, to provide both mean CSFP and CSFP pulse amplitude (CPA). Body Mass Index (BMI) was calculated from self-reported height and weight, along with age. Blood pressure (BP) was acquired in all 3 positions. Pulse pressure (PP) was calculated as systolic minus diastolic pressure. Linear regression analysis was performed between ICP and both age and BMI, as well as between PP and both OPA and CPA. Significance threshold was p < 0.05.

Results : BMI is significantly related to ICP (p < 0.0001, R² = .2389) in all subjects combined (Fig), as well as the NRM (p = 0.0171, R² = .1604) and POAG (p = 0.0134, R² = .2578) groups, but not NTG or OHT. Age has no relationship with ICP in any group. IOP has no relationship to ICP using DCT or PNT. OPA is significantly related to CPA using DCT (p = 0.005, R² = .1366), PNTsit (p = 0.0240, R² = .0628), PNTsup (p = 0.0036, R² = .0964), and PNTdur (p = 0.0002, R² = .1500). PPdur is significantly related to CPA (p = 0.0008, R² = .1316), and to OPA using DCT (p = 0.0115, R² = .0753), PNTsit (p = 0.0162, R² = .0767), PNTsup (p = 0.0001, R² = .1584), and PNTdur (p = 0.0007, R² = .1335). DCT OPA and IOP are significantly related (p = 0.0095, R² = .0842), as are PNT IOP and OPA in two of three positions (sit: p < 0.0001, R² = .01838; sup: p = 0.0035, R² = .1054; dur LP: p = .0534, R² = .0476).

Conclusions : BMI may be a confounding factor in interpreting differences in ICP between glaucomatous and normal subjects. Systemic pulse pressure is an important predictor of both OPA and CPA, which are correlated, and IOP is an additional predictor of OPA.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.