Table 1.
Abbreviations and their definitions of various corneal powers and astigmatisms.
Table 2.
Various mean net astigmatisms of preoperative and postoperative cornea.
Bivariate significance tests for differences between preoperative and postoperative astigmatisms of each subject were performed on 0 diopter @ 0° using Hotelling’s T2.
Table 3.
Univariate analysis of preoperative and postoperative Pearson’s r with SimKastig − Kastig.
Table 4.
Mean net astigmatisms of difference between various astigmatisms of the Pentacam and the Keratometer before and after surgery.
Bivariate significance test on 0 diopter @ (Φ + 0)° was performed using Hotelling’s T2.
Table 5.
Univariate analysis of the mean preoperative and postoperative values of TCRP4astig − Kastig, Bastig − KBastig, and RP4astig − Kastig.
Fig 1.
Postoperative comparison of differences in curvital power between front refractive astigmatism and keratometric astigmatism (Kastig).
The differences were calculated for 2-, 3-, and 4-mm zone front refractive astigmatisms (RP2astig − Kastig, RP3astig − Kastig, RP4astig − Kastig, respectively). The curvital power was calculated along the meridian of Kastig. The differences were significant, especially for RP4astig − Kastig (P = 0.005, repeated ANOVA; *P = 0.014, **P = 0.003, Turkey’s multiple comparisons test). Error bars represent the 95% confidence interval of the mean.
Fig 2.
Scatter plots and a regression line between the magnitude of keratometric astigmatism (Kastig) and the curvital power of (Bastig—KBastig) along Φ before (A) and after (B) surgery.
Bastig, simulated keratometer back astigmatism of the Pentacam; KBastig, keratometric back astigmatism; Φ, steep meridian of Kastig.
Table 6.
Comparison between arithmetic and coefficient adjustment methods before and after keratorefractive surgery.
Fig 3.
Scatter plots between the magnitude of keratometric astigmatism (Kastig) and adjustment factors before (A and C) and after (B and D) surgery.
TCRP4astig, 4-mm-apex zone total corneal refractive astigmatism; Φ, steep meridian of Kastig; KP(Φ), curvital power along Φ meridian; PRK, photorefractive keratectomy, LASIK, laser in situ keratomileusis
Fig 4.
Preoperative (A, B) and postoperative (C, D) adjustment effectiveness shown as pairs of polar values (diopters).
By arithmetic adjustment, thin line ellipse moves horizontally (arrows) and reaches thick line ellipse (A, C). By coefficient adjustment, the shape of ellipse is changed (B, D). Dashed thin circle, target circle for 0.75-D magnitude of astigmatism; thin line ellipse, 95% normal region of (TCRP4astig − Kastig); thick line ellipse, 95% normal region of (TCRP4astig − adjusted Kastig); Φ, steep meridian of Kastig in degrees; TCRP4astig, 4-mm-apex zone total corneal refractive astigmatism; Kastig, keratometric astigmatism.