Head-down Posture in Glaucoma Suspects Induces Changes in IOP, Systemic Pressure, and PERG That Predict Future Loss of Optic Nerve Tissue

Abstract

Purpose To obtain pilot data on posture-induced changes of IOP, systemic pressure and pattern electroretinogram (PERG) predictive of future optic nerve tissue loss glaucoma suspects (GS). Methods Mean peripapillary retinal fiber layer thickness (RNFLT) was measured with OCT two times/year in 28 GS aged 58 ± 8.9 years over 5.0 ± 0.73 years. All patients had a baseline PERG, IOP and brachial blood pressure measurements in the seated and – 10 degrees head-down-body-tilt position (HDT). Outcome measures were seated/HDT PERG amplitude and phase, IOP, mean arterial blood pressure (MAP), and estimated ocular perfusion pressure (OPP). An additional group of 11 similarly-aged controls (SAC) aged 56.9 ± 13 years was tested for comparison. Results While all GS had initial RNFLT in the normal range, 9/28 of them developed significant (P < 0.05) loss of mean RNFLT (thinners, T) over the follow-up period as opposed to 19/28 who did not (non-thinners, NT). Significant (P<0.05) differences between SAC, NT and T were found in PERG amplitude, PERG phase, MAP, IOP, and OPP. A nominal logistic regression using baseline PERG and hemodynamic variables was able to distinguish T from NT with an AUROC of 0.89 (SE 0.07). Conclusions Baseline PERG, IOP, and systemic blood pressure, together with their changes upon HDT, may have predictive value for future loss of optic nerve tissue in GS. This study supports the rationale for a full-scale clinical trial to identify patients at high-risk of development of glaucoma.

Interaction of intraocular pressure and ganglion cell function in open angle glaucoma

“…We observed a reversible reduction of ganglion cell responses as reflected by the ssPERG for LDP, especially in the lower eye. This is supported by a previous report on the effect of recumbent posture the ssPERG after 8 minutes of head-down body tilt (HDT) of -10° in a subpopulation of glaucoma suspects and early manifest glaucoma patients 8,9 . It was also shown in a longitudinal study that glaucoma suspects at higher risk for glaucoma conversion had more susceptibility to moderate HDT changes 9…”

“…Specifically, posture-induced IOP changes offer a straightforward option to manipulate IOP. For example, supine posture with -10° head down tilt in a subpopulation of glaucoma suspects was found to be associated with an increase in IOP and a decrease of PERG amplitude 8,9 . An increase in IOP was also reported during lateral decubitus posture (LDP) for both participants with healthy vision [10][11][12] and for glaucoma patients [13][14][15] .…”

Inflammasome Activation Induces Pyroptosis in the Retina Exposed to Ocular Hypertension Injury

“…The IOP spike-induced degeneration of RGCs has been demonstrated in a rodent model (Joos et al, 2010 ). Provided that the exposure to OHT episodes was observed during the head-down posture in aging people (Ventura et al, 2013 ; Porciatti et al, 2017 ), this mechanism could potentially contribute to glaucomatous-like degeneration of RGCs.…”

Haemodilution and head-down tilting induce functional injury in the rat optic nerve

“…The rationale is that there is no prone position (as in spine surgery) for rodents, but profound head down tilt increases intra-ocular and intracranial pressure and alters MRI-based parameters of cerebrospinal fluid dynamics in the optic nerve sheath. 8–11 Groups were 5 h supine (SUP), 5 h tilted head-down only (TILT), 5 h tilted head-down with haemodilution (TILT-HD) and 5 h SUP with haemodilution (SUP-HD). For isovolumic haemodilution, 2-ml blood was withdrawn from the venous catheter every 30 min over a 90-min period; during this time the animals remained positioned according to group assignment.…”