Abstract
Purpose :
Scleral rigidity can be measured indirectly using a novel, non-invasive, phase-sensitive optical coherence tomography (PhS-OCT) to detect pulsatile choroidal expansion, measured as choroidal maximal strain (CMS). This study evaluates the correlation between CMS and other ocular and systemic biometric parameters in patients with and without glaucoma.
Methods :
Participants with primary open-angle glaucoma (POAG), normal tension glaucoma (NTG), and normal eyes were recruited from Harborview Medical Center Eye Institute clinics. Cornea hysteresis (CH) was measured with non-contact tonometry [Ocular Response Analyzer]. Axial length (AL), intraocular pressure (IOP), mean ocular perfusion pressure (MOPP), and pulse pressure (PP) were recorded. One eye from each subject was scanned using swept-source OCT [Plex Elite 9000]. For each scan, a 3-mm line field centered at the fovea was continuously monitored for 13.6 seconds. Scans were processed, and CMS was extracted as the ratio of maximal deformation to choroidal thickness. A pairwise comparison was used to compare CMS between POAG, NTG, and normal eyes. Multiple linear regression was used to analyze associations with CMS.
Results :
The study included 36 patients (11 normal, 14 POAG, and 11 NTG); 52.8% were female with a mean age of 74.2 ± 6.6 years. Mean IOP, MOPP, PP, and CH were 12.5 ± 3.7, 50.9 ± 10.3, 62.0 ± 15.5, and 9.6 ± 1.4 mmHg, respectively. The mean CMS of NTG eyes was higher than both POAG and normal, but the difference is not significant (p=0.21, p=0.32, respectively). No difference was observed between normal and POAG (p=0.98). Multiple regression indicated associations between CMS and AL (p=0.011), PP (p=0.007), and CH (p=0.041), but not with IOP (p=0.828) and MOPP (p=0.407).
Conclusions :
CMS is a surrogate of scleral rigidity because the sclera provides the main resistance to choroidal expansion. This study found CMS is associated with CH, PP, and AL. The relation between CMS and CH suggests a correlation between the biomechanics of the cornea and the posterior sclera. In addition, the difference in CMS between POAG and NTG may provide insight into understanding biomechanical alterations implicated in glaucoma physiopathology.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.