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Eun Jung Lee, Jong Chul Han, Changwon Kee; Asymmetry in anterior lamina cribrosa surface tilting may contribute to retinal nerve fiber layer defect in myopia. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3562.
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© ARVO (1962-2015); The Authors (2016-present)
Factors associated with retinal nerve fiber layer (RNFL) defect development in myopic eyes are not clearly validated. We performed a retrospective study to investigate the factors associated with development of RNFL defect in myopic eyes, including optic nerve head morphology and anterior lamina cribrosa surface (ALCS) tilt.
We retrospectively reviewed medical records of myopic patients who visited department of Ophthalmology at Samsung Medical Center for examination of glaucoma. All participants underwent comprehensive ophthalmologic examinations including optic disc measurement with Cirrus HD spectral-domain optical coherence tomography (OCT). Eyes were divided into two groups of comparable degree of myopia, according to the presence of RNFL defect. Cup-to-disc ratio, ovality index, and torsion were measured manually using fundus photography. ALCS tilt angle was calculated by measuring the acute angle between ALCS and Bruch’s membrane opening plane in horizontal and vertical B-scans. Angle α was defined as ALCS tilt angle in horizontal B-scan, and angle β as in vertical B-scan. Angle δ was the difference between α and β, and we used absolute value of δ for analysis. Factors including optic nerve head parameters and tilt angles were compared between two groups.
In total, 34 eyes in group with RNFL defect, and 22 eyes without RNFL defect were analyzed. Spherical equivalent in two groups were -5.25 D and -5.07 D, respectively, and axial length was 26.3 and 25.6 mm, respectively. Age, intraocular pressure, ovality index and torsion were not significantly different between two groups, but ratio of peripapillary atrophy to disc area was significantly larger in group with RNFL defect (p=0.011) than in group without RNFL defect. Among tilt angles, α, β, and δ did not show significant difference, but |δ| was significantly larger in group with RNFL defect than in group without RNFL defect (11.62° and 6.29°, respectively, p=0.007, Table 1, Figure 1). In multivariate analysis, |δ| was related to the presence of RNFL defect (p=0.046).
Tilted disc morphology on funduscopic examination does not fully explain the development of RNFL defect. As observed in this study, deeper structural features as asymmetric ALCS tilt might have a role in RNFL damage, possibly through its twisted or distorted shape to strain the nerve axons.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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