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Table 2 Change in astigmatism based on the Alpins method of vector analysis

From: Comparison of outcomes after topography-modified refraction versus wavefront-optimized versus manifest topography-guided LASIK

Parameter (mean ± SD) WFO Manifest TG TMR P-value Post hoc (P-value)
TIA 0.90 ± 0.50 1.10 ± 0.74 1.17 ± 0.64 .035* TMR > WFO (.032)
SIA 0.99 ± 0.61 1.13 ± 0.77 1.40 ± 0.75 .002* TMR > WFO (.002)
DV 0.33 ± 0.31 0.29 ± 0.27 0.47 ± 0.35 .005* TMR > WFO (.026), Manifest TG (.014)
ME 0.08 ± 0.34 0.03 ± 0.31 0.23 ± 0.39 .007* TMR > WFO (.041), Manifest TG (.015)
CI 1.10 ± 0.46 1.09 ± 0.47 1.27 ± 0.51 .057  
IOS 0.50 ± 0.56 0.43 ± 0.53 0.53 ± 0.51 .607  
  1. WFO = wavefront-optimized; TG = topography-guided; TMR = topography-modified refraction; TIA = target-induced astigmatism; SIA = surgically-induced astigmatism; DV = difference vector; ME = magnitude of error; CI = correction index; IOS = index of success. *Statistically significant (P < .05)