Optic Disc Elschnig's Scleral Ring and Associated Factors among Glaucoma Patients: Primary Open-Angle African American Glaucoma Genetics (POAAGG) Study

Abstract

Purpose : The scleral ring, which surrounds the outer border of the optic disc when present, is an anatomical variation that is not presently well-studied in glaucoma. We evaluated the amount of visible scleral ring and its association with ocular and demographic characteristics of African ancestry glaucoma patients.

Methods : Optic disc features on stereo color images from cases in the Primary Open-Angle African American Glaucoma Genetics (POAAGG) study were independently evaluated by two non-physician graders. When a scleral ring was identified, the proportion of its area to the optic disc was calculated based on measurements in ImageJ. The association of amount of visible scleral ring with demographic, optic disc, and phenotypic characteristics was analyzed using univariable and multivariable regression models. The multivariable model included factors with p<0.25 from the univariable analysis and used backward variable selection to only keep factors with p<0.05 in the final multivariable model. Myopia status was an exception and included in the final multivariable model. The inter-eye correlation was accounted for using generalized estimating equations.

Results : A visible scleral ring was present in 3310 out of 3319 (99.7%) eyes of glaucoma cases. Among 1813 eyes with complete data within a six-month time period of the image date, the median (1^st quartile, 3^rd quartile) for proportion of scleral ring was 0.143 (0.109, 0.180). The proportion of scleral ring was greater in eyes with oval discs compared to round discs (p=0.04) and in eyes with stereoscopically diagnosed tilted disc compared to no tilted discs (p=0.008). It was lower in eyes with conus pigmentosus (p<0.001), discs with grey crescent (p<0.001), higher cup-to-disc areas (p<0.001), discs with nasalization of the central vessels (p=0.02), and discs with visible pores of the lamina cribrosa (p<0.001) (Table 1). The proportion of scleral ring was not associated with myopic status (p=0.60).

Conclusions : Almost all glaucoma cases in our African ancestry cohort had a visible scleral ring. The proportion of scleral ring-to-disc area was associated with several optic disc features. Lower proportion observed in eyes with higher cup-to-disc ratio, nasalization of central vessels, and visible lamina cribrosa pores suggests that this observation may be associated with more severe glaucoma.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.