IOP-induced ONH strains negatively tied to retinal sensitivity in glaucoma patients
Optic nerve head (ONH) strains under intraocular pressure (IOP) show a negative association with retinal sensitivity in patients with open-angle glaucoma, according to a study. In particular, high-tension glaucoma (HTG) patients with higher ONH strains are more likely to show lower retinal sensitivities.
“Interestingly, this trend in general was less pronounced in patients with normal-tension glaucoma (NTG), which could suggest a distinct pathophysiologic relationship between the two glaucoma subtypes,” the researchers said.
A total of 229 patients with primary open-angle glaucoma (115 with HTG and 114 with NTG) were included in this clinic-based cross-sectional study. Using optical coherence tomography, the researchers diagnosed ONH for one eye of each patient under the following conditions: primary gaze and primary gaze with acute IOP elevation (approximately 35 mm Hg) achieved through ophthalmodynamometry.
IOP-induced ONH tissue strain (ie, deformation) in each ONH was quantified via 3-dimensional strain-mapping algorithm. Using linear regression, strains in the prelaminar tissue (PLT), the retina, the choroid, the sclera, and the lamina cribrosa (LC) were associated with measures of retinal sensitivity from the 24-2 Humphrey visual field test. The researchers performed this globally, then locally based on a previously published regionalization scheme.
Significant negative linear associations were found between ONH strains and retinal sensitivity in patients with HTG (p<0.001; on average, a 1-percent increase in ONH strains corresponded to a 1.1-decibel reduction in retinal sensitivity). In addition, the researchers found that high-strain regions colocalized with anatomically mapped regions of high visual field loss. They also noted the strongest negative associations in the superior region and in the PLT.
For patients with NTG, ONH strains showed no significant associations with retinal sensitivity, except in the superotemporal region of the LC.