Primary open-angle glaucoma (POAG) is more prevalent and more severe in Black populations compared with white subjects. The reason for this is unknown, but researchers believe differences in ocular biomechanics may play a role. Joshua Canavan, an OD candidate at Ohio State University, presented his group’s findings on this topic in a poster session last week at the ARVO 2021 virtual meeting. The researchers investigated corneal and scleral stiffness responses in healthy eyes of sub-Saharan African, European and mixed-race individuals to gather baseline data and found scleral stiffness may contribute to POAG.
The adult subjects included in the study had no history of ocular disease. They were categorized by self-reported ancestry: sub-Saharan African (n=40 eyes, mean age 37, 65% female), European (n=84 eyes, mean age 35, 60% female) and mixed-race (n=36 eyes, mean age 32, 61% female). The researchers measured corneal hysteresis, central corneal thickness and biomechanically corrected intraocular pressure to derive in vivo parameters of corneal and scleral (SP-HC) stiffness.
In the question-and-answer virtual chat, Mr. Canavan explained that scleral stiffness was derived from the Corvis ST (Oculus) and calculated as the “difference between corneal deflection amplitude at maximum capacity and at first applanation.” He noted, “It also considers the load imposed on the cornea by the device. The scleral limits the maximum deformation of the cornea in response to the air puff, so SP-HC is a biomarker for scleral stiffness.”
His team found no significant difference between the three ancestry cohorts in corneal hysteresis, corneal stiffness, Goldmann applanation tonometry, IOP, Pascal dynamic contour tonometry, IOP or central corneal thickness. Mean scleral stiffness was as follows:
- 14.37mm Hg/mm in the sub-Saharan African cohort
- 13.86mm Hg/mm in the European cohort
- 14.72mm Hg/mm in the mixed-race cohort
The researchers noted that when adjusted for central corneal thickness and higher IOP in the mixed-race cohort, mean scleral stiffness was significantly higher among sub-Saharan African individuals than the other two cohorts.
They concluded that individuals of sub-Saharan African descent may have greater scleral stiffness, independent of other ocular biomechanical parameters. They believe this may contribute to the pathophysiology of POAG. “The ramifications of this finding warrant further investigation,” said Mr. Canavan.
Canavan J, Koons A, Mahmoud A, et al. Corneal and scleral biomechanical differences among individuals of Sub-Saharan African, European and mixed-race descent. ARVO 2021 annual conference.