Higher optic nerve sheath diameters are associated with lower ocular blood flow velocities in glaucoma patients

Abstract

To investigate the relationship between optic nerve sheath diameter (ONSD) and retrobulbar blood flow velocities, as measured by color Doppler imaging (CDI) in glaucoma patients. We performed a prospective, randomized, observer-masked study involving a total of 197 subjects. Once enrolled, they were divided by three groups: healthy controls (n = 51), normal-tension glaucoma patients (NTG, n = 58), and primary, open-angle glaucoma patients (POAG, n = 88). All subjects underwent a general ophthalmological examination, an ultrasound-based assessment of the ONSD, and a hemodynamic study of the retrobulbar vascularization using CDI. Non-parametric tests, chi-square contingency tables, and the Deming correlations were used to explore differences and correlations between variables in the diagnostic groups. ONSD was not different between experimental groups (p = 0.28). ONSD correlated positively with the pulsatility index of the ophthalmic artery in healthy individuals (p = 0.007), but not in glaucoma patients (NTG: p = 0.41; POAG: p = 0.22). In NTG patients, higher ONSD values were associated with lower end-diastolic and mean flow velocities in the short ciliary arteries (p = 0.005 in both correlations). No such correlation was found in healthy nor POAG groups (p range between 0.15 to 0.96). ONSD was not associated with any CDI-related variable of the central retinal artery in any cohort. Venous outflow velocities were not associated with ONSD in any of the three groups. ONSD is negatively correlated with retrobulbar blood flow velocities in glaucoma patients, but not in healthy controls.