Evaluation of Ocular Pulse Amplitude-related Parameters measured by Dynamic Contour Tonometry and Ocular Blood Flow Analyzer

Abstract

We performed this study to evaluate ocular rigidity-related factor (ORF) derived from ocular pulse amplitude (OPA) measurements with regard to the severity of glaucoma.

This study was conducted in 31 eyes of 31 normal and 38 eyes of 38 normal tension glaucoma (NTG) patients with cross-sectional and retrospective design. OPA was measured using dynamic contour tonometry (DCT). Pulse amplitude (PA), pulse volume (PV), and pulsatile ocular blood flow (POBF) were measured using ocular blood flow analyzer (OBFA). Intraocular pressure (IOP) was measured by Goldmann applanation tonometry (GAT), DCT and OBFA. ORF was calculated from OPA and PV, measured with both devices, based on the Friedenwald equation. ORF = [log (DCT IOP + OPA) - log DCT IOP]/PV. The severity of glaucoma was estimated by both mean deviation (MD) of visual field (VF) tests and retinal nerve fiber layer (RNFL) thickness of Stratus optical coherence tomography (OCT) in medically treated NTG patients.

Both IOP and OPA of NTG patients were lower than those of normal subjects whereas PA, PV and POBF was not significantly different between groups. The calculated ORF of NTG patients did not differ from that of normal subjects. OPA showed significant correlation with IOP measured by both GAT and DCT but PA did not. OPA and POBF correlated significantly with the spherical equivalent of refractive error but not with central corneal thickness and blood pressure. Both POBF and ORF were significantly correlated with IOP measured by all the three devices. Although OPA and POBF did not correlate with glaucoma severity, ORF showed significant correlation with MD of VF and RNFL thickness measured by OCT in NTG patients.

Although both OPA and POBF significantly correlated with IOP level, they did not correlate with the severity of glaucoma. ORF, derived from measurements of ocular pulse amplitude, could be related to the severity of glaucoma in treated NTG patients.