Disturbed correlation between arterial resistance and pulsatility in glaucoma patients

Abstract

ABSTRACT.Purpose: (i) To investigate whether pulsatility index (PI) and mean flow velocities (MFV) are altered in glaucoma patients. (ii) To evaluate the significance of PI in retrobulbar autoregulation capacity. Methods:Patients with primary open-angle glaucoma (POAG; n = 49), normal tension glaucoma (NTG; n = 62) and healthy controls (n = 48) underwent colour Doppler imaging measurements of the retrobulbar vasculature. Kruskal-Wallis test was used to compare variables between the three diagnostic groups. Restricted cubic splines were used to determine nonlinearities between the resistive index (RI) and PI correlations. Results: Mean flow velocities (MFV) were lower in both short posterior ciliary arteries (SCPA) and central retinal arteries (CRA) from the two glaucoma groups (p < 0.04 versus healthy controls). No differences were detected in RI or PI in any arteries of the three diagnostic groups (p > 0.08). In healthy individuals, correlations between RI and PI were linear in all arteries. In both POAG and NTG patients, CRA presented a nonlinear curve with a cutpoint at RI 0.77 (p < 0.001) and 0.61 (p = 0.03), respectively, above which the slope increased nearly five-and tenfold (POAG: 1.96 to 10.06; NTG: )0.46-4.06), respectively. A nonlinear correlation in the ophthalmic artery was only observed in NTG patients, with a cutpoint at RI 0.82 (p < 0.001), above which the slope increased from 3.47 to 14.03. Conclusions: Glaucoma patients do not present the linear relationships between RI and PI observed in healthy individuals. Their nonlinear relations may be indicative of an altered autoregulation and suggest a possible threshold RI could be determined above which autoregulatory disturbances become more relevant.

Oestrogen, ocular function and low-level vision: a review

“…This is important given that contrast sensitivity decreases after menopause, improves after HRT and is affected by normal cycling oestrogen. Coupled with evidence that reduced retinal blood flow may act as a precipitant in the development of glaucoma and AMD (Harris et al 1999, Flammer et al 2002, Pinto et al 2012, these findings support the idea that post-menopausal oestrogen deficiency may, at least circuitously, dispose older females to these age-related ocular diseases.…”

Vascular considerations in glaucoma patients of African and European descent

“…Similarly, a newly published prospective study by Adeyinka et al measured retrobulbar blood flow velocities in African patients with OAG in Nigeria and found reduced peak systolic and end diastolic velocities and increased resistivity in the ophthalmic and central retinal arteries of OAG patients compared to controls (Adeyinka et al 2013). Previous studies have demonstrated a reduction in blood flow velocities in the retrobulbar vessels of glaucoma patients in general (Sergott et al 1994; Nicolela et al 1996; Chiou et al 1999; Akarsu and Bilgili 2004; Abegão Pinto L et al 2012), and lower retrobulbar blood flow within in OAG patients of AD may be a mechanism which contributes to their OAG disease disparity. Importantly, vascular resistance of retrobulbar vessels has been shown to predict visual field progression (Martinez et al 2005); similarly, constricted blood flow has been associated with visual field loss (Galassi et al 2003).…”

Is There Any Role for the Choroid in Glaucoma?

“…70-72 However, the interaction of these vascular systems may play an important role in keeping the ONH healthy. 70 In the early 1970s, contrary results were reported in the regulatory behavior of ChBF during experimental manipulation of ocular perfusion pressure (OPP).…”