The Effect of Systemic Hyperoxia on Optic Nerve Head Blood Flow in Glaucoma

Abstract

Purpose : It has been suggested that dysfunctional autoregulation of optic nerve head blood flow is associated with the pathology of glaucoma. Thus, methods to evaluate autoregulatory capacity are needed. Previously, we described a laser speckle flowgraphy-based method to quantify autoregulatory capacity during oxygen inhalation in normal subjects (Shiga Y et al. 2014). Here, we evaluate this technique in open-angle glaucoma (OAG) patients.

Methods : This study comprised 12 eyes of 12 OAG patients (age: 54.4 ± 12.7 years, mean deviation: -3.4 ± 4.0 dB) and 12 age-matched eyes of 12 normal subjects (age: 55.2 ± 8.1 years). The testing protocol had three stages: baseline, hyperoxia (12 min of pure oxygen at 6L/min), and recovery (4 min of room air). Before and after oxygen inhalation, we evaluated optic nerve head blood flow according to the mean blur rate (MBR), an LSFG-derived variable. We measured blood pressure (BP), heart rate (HR), and peripheral capillary oxygen saturation (SpO₂) every 5 min.
Ocular perfusion pressure (OPP) was calculated using baseline IOP. We compared the variables at each measured time point in both groups.

Results : No significant changes were seen in BP, HR, or OPP (P = 0.39-0.98) during the testing despite a significant increase in SpO₂ during hyperoxia in both groups (P < 0.0001). MBR was significantly higher during hyperoxia in the OAG patients than in the normal subjects (90.7 ± 8.8% vs. 85.0 ± 4.6%, respectively, P = 0.04; baseline = 100% in both).

Conclusions : The response to hyperoxia was significantly lower in the OAG patients. This result may indicate that autoregulation becomes dysfunctional in glaucoma.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.