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Sieun Lee, Morgan L Heisler, Winsey Chui, Marinko V Sarunic, Paul J Mackenzie, Mirza Faisal Beg; Effects of myopia and glaucoma in anterior lamina cribrosa and prelaminar scleral canal structure. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3166.
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© ARVO (1962-2015); The Authors (2016-present)
Structural changes in the lamina cribrosa (LC) region are central in the biomechanical paradigm of glaucoma. The purpose of this study is to examine the structural characteristics in in-vivo anterior LC and prelaminar scleral canal in connection with age, axial length, and glaucoma severity in myopic normal and glaucomatous subjects, and to study the interplay of the two conditions changing the optic nerve head structure.
38 myopic normal eyes and 65 myopic glaucomatous eyes were imaged using a 1060nm custom swept-source optical coherence tomography (SS-OCT) system. Bruch's membrane opening (BMO), anterior lamina insertion points (ALIP), and anterior LC surface (ALCS) were segmented. Expansion, elongation, and skew of the prelaminar scleral canal were characterized by the area, eccentricity, and planarity of BMO and ALIP, and relative distances. ALCS depth and relative planarity were measured. Multiple regression analysis was performed to assess the effect of age, axial length (AL) and visual field loss quantified by mean deviation (MD) on the shape parameters.
In the normal myopic eyes, increased AL was associated with larger BMO (p = .0003) and ALIP areas (p = 0.014), and longer (p = .0001) more skewed (p = .0008) canal. Increased AL was also associated with less axial bowing of ALCS (p = .0016), likely due to the canal expansion and the LC being pulled taut. This was also consistent with the posterior bowing of BMO negatively correlated with AL (p = .018).In the glaucomatous myopic eyes, increased AL was similarly associated with larger BMO (p = .0027) and ALIP areas (p = .011) and canal skew (p = .025), along with reduced ALCS bowing (p= .011). However, severity of glaucoma (increased MD magnitude) was associated with increased posterior bowing of BMO (p= .004) and ALCS (p = .013).
Increased AL due to myopia is associated with expanded, elongated, and skewed prelaminar scleral canal. The negative relationship between axial bowing of the ALCS and AL supports the hypothesis that lateral "trampolining" forces may contribute to the anterior position of the lamina in normal and glaucomatous myopes, with posteriorization of ALCS position with increasing severity of glaucoma. This complex and increased stress on anterior LC may be involved in the increased glaucoma susceptibility of high myopes. Measure of LC bowing in glaucoma is confounded by myopia.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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