The daily ebb and flow of peripapillary and macular vessel density (VD) may not be directly linked to changes in intraocular pressure (IOP), according to a new study.1

Researchers enrolled 37 patients with open-angle glaucoma in this prospective, observational cross-sectional study. They performed optical coherence tomographic angiography imaging and IOP measurements at 08:00, 11:00, 14:00 and 16:00 time-points on a single day. At each session, two scan protocols were used to generate three-dimensional en face OCT angiograms: a 4.5mm-by-4.5mm scan centered on the optic nerve head and 6mm-by-6mm scan centered on the fovea. For each scan mode, the researchers calculated the radial peripapillary capillary segment, composed of the retinal nerve fiber layer and ganglion cell layer vasculature.

Researchers found the optic nerve head and peripapillary VD measurements at 14:00 and 16:00 time-points were greater than the measurements at 08:00 and 11:00. The 14:00 and 16:00 VD measurements were statistically significantly greater (p<0.05) than the 08:00 measurements for the whole en face, inside disc and average peripapillary VDs. The macular VD measurements at the 14:00 time-point were greater than the measurements at 08:00 and 11:00 time-points.

Investigators also reported diurnal changes were small and clinically insignificant.

1. Mansouri I, Rao HL, Hoskens K, et al. Diurnal variations of peripapillary and macular vessel density in glaucomatous eyes using optical coherence tomography angiography. J Glaucoma. 2018 Apr;27(4):336-41.