Abstract
Purpose :
To quantify biomechanical properties on different scleral locations using Optical Coherence Elastography (OCE), and to evaluate the effects of Rose Bengal-Green Light (RGX) crosslinking in scleral stiffening.
Methods :
Five freshly enucleated rabbit eyes (24-48h post-mortem) from adult New Zealand white rabbits were measured at four sclera locations (superior/inferior temporal (ST, IT) and nasal (SN, IN)). Elastic waves were induced in the sclera with a small contact probe (diam. 2mm) vibrating at 2 kHz. Wave propagation speeds (WPS) were calculated from images taken with a phase-sensitive swept source optical coherence tomography system in three meridians, vertical (90°), oblique (135°) and horizontal (180°). Intraocular pressure was fixed at 15 mmHg. RGX (523nm, 0.1W/cm2, 400s) was applied on the temporal side of the sclera. OCE measurements were performed before and after RGX. Subsequently, scleral strips were extracted and used for stress-strain measurements (uniaxial stretcher, CellScale, Canada). Young’s modulus (YM) was calculated at 8% strain.
Results :
WPS in untreated scleral tissue ranged approximately from 5 to 40 m/s. Mean WPS was calculated per each scleral region. Multi-meridional analysis showed differences in WPS across ST: 25m/s (90°), 22m/s (135°), 19m/s (180°); IT: 21m/s (90°), 22m/s (135°), 21m/s (180°); SN: 21m/s (90°),16m/s (135°), 15m/s (180°); and IN: 18m/s (90°), 26m/s (135°), 11m/s (180°). After RGX, WPS increased in IT region (0.7% (90°), 12% (135°). IN region showed the lowest measured WPS (16m/s (135°), 10m/s (180°)). Uniaxial stretching showed that RGX produced 30% increase in stiffness compared with the contralateral untreated sclera. At 8% strain, the estimated YM of RGX-treated tissue were 11.3±7.0MPa(ST), 11.2±4.4MPa(IT), and of untreated tissue were 7.9±6.7MPa(SN), 7.2±4.1MPa(IN), suggesting a vertical WPS to stiffness ratio of 2 and 3 in temporal and nasal regions, respectively.
Conclusions :
Wave propagation speed is dependent on scleral location and direction. Both WPS and YM reveal variations of the scleral properties by Rose-Bengal cross-linking, with regional differences in efficiencies. OCE appears as a promising, non-invasive method to quantify the efficacy of scleral stiffening myopia treatments.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.