Fig. 6
Schematic diagrams showing the influence of corneal ablation patterns on prediction errors after cataract surgery in post-myopic-LASIK eyes. T1, T2, T3 and T4 refer to the thickness of the ablation zone at the corneal vertex, while T3’ and T4’ refer to the ablation center. a The left two diagrams show a well-centered and a decentered ablation with equal ablation amount. When the ablation is decentered, the thickness of the ablation zone at the corneal vertex is thinner than expected (T2 < T1). Therefore, the relationship between the anterior and posterior corneal surfaces has further changed, leading to extra errors of available formulas which are based on well-centered ablation models. b The right two diagrams show different number of ablations with equivalent magnitude of decentration. When the amount of ablation is small, the variation in the thickness across the ablation zone is limited (δT3 < δT4; δT3 = T3’ − T3, δT4 = T4’ − T4). Therefore, the change in the relationship between anterior and posterior corneal surfaces induced by ablation zone decentration and its consequent influence on prediction errors might be negligible. However, when the amount of ablation is large, its effects should not be ignored