Abstract
Purpose :
In the recent Boramae Myopia Cohort Study, we found a shift of lamina cribrosa (LC) in contrast to the relatively preserved the Bruch membrane opening (BMO) during axial elongation. Subsequently, we showed the direction and extent of LC shift, which was estimated by the deviation of the central retinal vascular trunk from the center of the BMO, was highly associated with the location of glaucomatous damage in myopic normal-tension glaucoma. We investigated whether LC shift is associated with the preferential location of glaucomatous damage in myopic high-tension open-angle glaucoma (OAG) eyes.
Methods :
LC shift was defined as a deviation of the central retinal vascular trunk from the center of the Bruch’s membrane opening (BMO), which was delineated by OCT imaging. The angular deviation was measured with the horizontal nasal midline as 0° and the superior location as a positive value. The shift index was calculated as the distance of the vascular trunk from the BMO center relative to that of the BMO margin. The preferential location of glaucomatous damage was determined retrospectively. The hemisphere of larger retinal nerve fiber layer (RNFL) defect, which was associated with worse pattern deviation compared to the opposite side, was defined as the dominant hemisphere based on their initial examination results. If we could not determine the hemispheric dominancy, the eye was classified as bi-equivalent involvement.
Results :
At their final visits, both hemispheres were involved in 67 (83%) eyes from total 81 high-tension OAG eyes. In the earlier periods, however, the glaucomatous damage showed inter-hemispheric asymmetry: dominant defect in the inferior hemisphere in 29 (36%) eyes, superior hemisphere in 22 (27%) eyes, and bi-equivalent in 30 (37%) eyes. A logistic regression analysis revealed that the inferior direction of LC shift was the only associated factor of the more damage in the superior hemisphere at initial visit (OR = 0.839, P = 0.002, Fig 1).
Conclusions :
Although the high intraocular pressure affected both hemispheres eventually, the LC in the direction opposite to the shifting was preferentially damaged during earlier course of disease. This implies that LC shift, as a result of differential growth between the retina and sclera, could increase the vulnerability of given optic nerve head.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.