Peripapillary sclera exhibits a v-shaped configuration that is more pronounced in glaucoma eyes

Author(s): Xiaofei Wang (1), Tin A Tun (2,3), Monisha Esther Nongpiur (3,4), Hla M Htoon (3), Yih Chung Tham (3), Nicholas G Strouthidis (5,6), Tin Aung (3,4,7), Ching-Yu Cheng (3), Michael Ja Girard (8,4)

1 Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Centre for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing, China.
2 Ophthalmic Engineering & Innovation Laboratory, Singapore Eye Research Institute, Singapore.
3 Singapore Eye Research Institute, Singapore National Eye Centre, Singapore.
4 Duke-NUS Medical School, Singapore.
5 Moorfields Eye Hospital NHS Foundation Trust, London, UK.
6 Discipline of Clinical Ophthalmology and Eye Health, University of Sydney, Sydney, New South Wales, Australia.
7 Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
8 Ophthalmic Engineering & Innovation Laboratory, Singapore Eye Research Institute, Singapore
mgirard@ophthalmic.engineering.

AIMS: To compare the shape of the anterior surface of the peripapillary sclera (PPS) between glaucoma and healthy subjects.

METHODS: 88 primary open angle glaucoma (POAG), 98 primary angle closure glaucoma (PACG) and 372 age-matched and gender-matched healthy controls were recruited in this study. The optic nerve head of one randomly selected eye of each subject was imaged with spectral domain optical coherence tomography. The shape of the PPS was measured through an angle defined between a line parallel to the nasal anterior PPS boundary and one parallel to the temporal side. A negative value indicated that the PPS followed an inverted v-shaped configuration (peak pointing towards the vitreous), whereas a positive value indicated that it followed a v-shaped configuration.

RESULTS: The mean PPS angle in normal controls (4.56±5.99°) was significantly smaller than that in POAG (6.60±6.37°, p=0.011) and PACG (7.90±6.87°, p<0.001). The v-shaped PPS was significantly associated with older age (β=1.79, p<0.001), poorer best-corrected visual acuity (β=3.31, p=0.047), central corneal thickness (β=-0.28, p=0.001), peripapillary choroidal thickness (β=-0.21, p<0.001) and presence of POAG (β=1.94, p<0.009) and PACG (β=2.96, p<0.001). The v-shaped configuration of the PPS significantly increased by 1.46° (p=0.001) in healthy controls for every 10-year increase in age, but not in glaucoma groups.

CONCLUSIONS: The v-shaped configuration of the PPS was more pronounced in glaucoma eyes than in healthy eyes. This posterior bowing of the PPS may have an impact on the biomechanical environment of the optic nerve head.

Br J Ophthalmol. 2020 Dec 17;bjophthalmol-2020-317900. doi: 10.1136/bjophthalmol-2020-317900. Online ahead of print.

PMID: 33334817

Keywords: glaucoma; imaging; sclera and episclera

Experimental Paper of the Month manager: Marta Pazos