Colm McAlinden1, Jonathan E Moore. 1. School of Biomedical Sciences, University of Ulster, Cromore Road, Coleraine, BT52 1SA, UK. colm.mcalinden@gmail.com
Abstract
BACKGROUND: In virgin eyes, the internal aberrations compensate corneal aberrations, and it has been suggested that the compensation may be feedback-driven and developmental, with active or passive adaptive mechanisms potentially responsible for the aberration auto-compensation. The purpose of this study is to investigate the internal higher order aberrations (HOA) following laser in situ keratomileusis (LASIK). METHODS: Prospective corneal and internal HOA were measured pre-operatively and 6 months post-operatively on 50 consecutive LASIK patients with the OPD-Scan. RESULTS: There were increases to corneal HOA terms Z⁰₄ (0.215 ± 0.092 μm to 0.381 ± 0.180 μm), Z⁰₆ (0.002 ± 0.018 μm to 0.049 ± 0.034 μm) and Z⁴₆ (0.010 ± 0.017 μm to 0.018 ± 0.016 μm) with corresponding increases to internal HOA terms Z⁰₄ (-0.176 ± 0.102 μm to -0.218 ± 0.121 μm), Z⁰₆ (0.004 ± 0.022 μm to -0.010 ± 0.036 μm) and Z⁴₆ (0.008 ± 0.106 μm to -0.015 ± 0.054 μm). The increases in internal aberrations attenuated the increase in corneal aberrations, providing an overall lower quantity of total aberration. A greater increase in corneal spherical aberration and associated compensation was found to occur with greater degrees of attempted myopic correction. CONCLUSION: Corneal spherical aberration and Z⁴₆increased with corresponding increases in the internal spherical aberration and Z⁴₆ following LASIK. This may be an active compensatory mechanism of the internal optics to change, in order to reduce the effect of induced corneal HOA.
BACKGROUND: In virgin eyes, the internal aberrations compensate corneal aberrations, and it has been suggested that the compensation may be feedback-driven and developmental, with active or passive adaptive mechanisms potentially responsible for the aberration auto-compensation. The purpose of this study is to investigate the internal higher order aberrations (HOA) following laser in situ keratomileusis (LASIK). METHODS: Prospective corneal and internal HOA were measured pre-operatively and 6 months post-operatively on 50 consecutive LASIK patients with the OPD-Scan. RESULTS: There were increases to corneal HOA terms Z⁰₄ (0.215 ± 0.092 μm to 0.381 ± 0.180 μm), Z⁰₆ (0.002 ± 0.018 μm to 0.049 ± 0.034 μm) and Z⁴₆ (0.010 ± 0.017 μm to 0.018 ± 0.016 μm) with corresponding increases to internal HOA terms Z⁰₄ (-0.176 ± 0.102 μm to -0.218 ± 0.121 μm), Z⁰₆ (0.004 ± 0.022 μm to -0.010 ± 0.036 μm) and Z⁴₆ (0.008 ± 0.106 μm to -0.015 ± 0.054 μm). The increases in internal aberrations attenuated the increase in corneal aberrations, providing an overall lower quantity of total aberration. A greater increase in corneal spherical aberration and associated compensation was found to occur with greater degrees of attempted myopic correction. CONCLUSION: Corneal spherical aberration and Z⁴₆increased with corresponding increases in the internal spherical aberration and Z⁴₆ following LASIK. This may be an active compensatory mechanism of the internal optics to change, in order to reduce the effect of induced corneal HOA.