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Alan J. Lang, Keith Holliday, Arturo Chayet, Enrique Barragán-Garza, Nikhita Kathuria; Structural Changes Induced by a Corneal Shape-Changing Inlay, Deduced From Optical Coherence Tomography and Wavefront Measurements. Invest. Ophthalmol. Vis. Sci. 2016;57(9):OCT154-OCT161. doi: 10.1167/iovs.15-18858.
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Changes to the anterior stroma and epithelium induced by a meniscus-shaped corneal inlay are presented. The hypothesis that local curvature is a driver of epithelial remodeling is tested.
Records of 30 subjects enrolled in a prospective clinical investigation of the inlay, implanted in emmetropic presbyopic subjects, were analyzed. The change to the anterior corneal surface was measured using wavefront techniques. The epithelial thinning profile was measured using Fourier domain optical coherence tomography. The stromal change was calculated from the two measurements.
The inlay's volume displaced the stroma anterior to the inlay, which was reflected in the change of Bowman's layer shape. The epithelium anterior to the inlay thinned by 18.4 ± 7.1 μm. Peripheral to the inlay's diameter (2 mm), circumferential epithelial thickening extended the change to the anterior corneal surface to approximately twice the inlay diameter. The central anterior corneal surface rose by 9.8 ± 3.4 μm, creating a progressive add power profile. The epithelial thinning was linearly related to the curvature of the alteration to the anterior surface height, consistent with a theoretical model.
When a meniscus-shaped corneal inlay is placed beneath a corneal flap, the flap's stroma takes on predominately the inlay's shape. The epithelium remodels within a zone approximately twice the inlay diameter, with an anterior corneal height change providing improved near and intermediate vision. The relationship between the epithelial, stromal, and anterior corneal surface changes confirms the hypothesis that epithelial changes are greatest in regions of greater local surface curvature.
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