Actual AP ratio in M-LVC eyes according to axial length (AL) and correlations between AP ratio and various biometric parameters
Patient characteristics and ocular biometric parameters of the M-LVC and control groups are shown in Table 1. The M-LVC group consisted of 1,018 eyes of 635 patients (209 men, 426 women) and had a mean age of 45.5 ± 11.1 (range, 20–81) years. The control group consisted of 19,841 eyes of 10,406 patients (4,995 men, 5,411 women) and had a mean age of 44.0 ± 26.5 (range, 20–98) years. The mean AP ratio was significantly higher in the M-LVC group (1.24 ± 0.05 [range, 1.07–1.54]) than in the control group (1.13 ± 0.02 [range, 1.04–1.54], p < 0.001, Mann–Whitney U test). The mean AL was significantly longer in the M-LVC group (26.40 ± 1.69 [range, 21.59–34.20] mm) than in the control group (24.67 ± 1.77 [range, 15.11–36.82] mm, p < 0.001, Mann–Whitney U test). All biometric parameters (anterior corneal radius, posterior corneal radius, CCT, keratometry, and TK), except ACD (p = 0.11), were significantly different between the two groups (p < 0.001, Mann–Whitney U test).
Table 1
Patient Demographics and Ocular Biometric Parameters of the Myopic Laser Vision Correction Group, Subgroups Classified by Axial Length, and Control Group.
| M-LVC group | Control group | P-value* |
Total | Group 1 AL < 26.0 mm | Group 2 26.0 mm ≤ AL < 28.0 mm | Group 3 28.0 mm ≤ AL < 30.0 mm | Group 4 30.0 mm ≤ AL |
Eyes | 1,018 | 463 | 406 | 111 | 38 | 19,841 | |
Age (years) | 45.5 ± 11.1 | 45.5 ± 11.1 | 44.1 ± 10.5 | 47.4 ± 12.4 | 52.5 ± 7.8 | 44.0 ± 26.5 | < 0.001 |
M:F | 209:426 | | | | | 4,995:5,411 | < 0.001 |
Ant. corneal radius (mm) | 8.61 ± 0.49 | 8.27 ± 0.01 | 8.83 ± 0.01 | 9.03 ± 0.04 | 9.21 ± 0.11 | 7.72 ± 0.27 | < 0.001 |
Post. corneal radius (mm) | 6.90 ± 0.28 | 6.78 ± 0.01 | 6.99 ± 0.01 | 7.05 ± 0.02 | 6.96 ± 0.07 | 6.80 ± 0.27 | < 0.001 |
AP ratio† | 1.24 ± 0.05 | 1.22 ± 0.04 | 1.26 ± 0.05 | 1.28 ± 0.05 | 1.32 ± 0.07 | 1.13 ± 0.02 | < 0.001 |
CCT (mm) | 0.48 ± 0.04 | 0.49 ± 0.00 | 0.47 ± 0.00 | 0.47 ± 0.00 | 0.48 ± 0.00 | 0.54 ± 0.03 | < 0.001 |
AL (mm) | 26.40 ± 1.69 | 25.03 ± 0.03 | 26.85 ± 0.02 | 28.73 ± 0.05 | 31.29 ± 0.17 | 24.67 ± 1.77 | < 0.001 |
ACD (mm) | 3.44 ± 0.31 | 3.36 ± 0.01 | 3.50 ± 0.01 | 3.57 ± 0.03 | 3.54 ± 0.04 | 3.39 ± 0.46 | 0.11 |
Keratometry (D) | 39.29 ± 2.23 | 40.85 ± 0.07 | 38.25 ± 0.07 | 37.48 ± 0.20 | 36.83 ± 0.50 | 43.74 ± 1.53 | < 0.001 |
Total keratometry (D) | 38.75 ± 2.40 | 40.42 ± 0.07 | 37.64 ± 0.08 | 36.81 ± 0.22 | 35.99 ± 0.52 | 43.73 ± 1.54 | < 0.001 |
Values are presented as mean ± standard deviation. |
*Mann–Whitney U test was performed between the M-LVC and control groups. |
†The Friedman test with Bonferroni post-hoc correction, all p-values < 0.001 between the AP ratio of each subgroup of M-LVC according to AL |
Statistical significance was defined as p < 0.05. |
M-LVC, myopic laser vision correction; AP, anterior-posterior; CCT, central corneal thickness; AL, axial length; ACD, anterior chamber depth |
We classified the M-LVC group into four subgroups according to the AL; Group 1 (463 eyes, AL < 26.0 mm), Group 2 (406 eyes, 26.0 mm \(\le\) AL < 28.0 mm), Group 3 (111 eyes, 28.0 mm \(\le\) AL < 30.0 mm), and Group 4 (38 eyes, AL > 30.0 mm). The AP ratio was significantly different among the groups (1.22 ± 0.04, 1.26 ± 0.05, 1.28 ± 0.05, and 1.32 ± 0.07; p < 0.001, Friedman test with Bonferroni post-hoc correction, Fig. 1).
In the correlation analysis, the AP ratio was significantly correlated with all the other biometric parameters in the control group (p < 0.001, Spearman’s rank correlation coefficient) and with all parameters, except ACD (p = 0.219), in the M-LVC group (p < 0.001, Spearman’s rank correlation coefficient). Considering the correlation coefficients, weak correlations were observed in the control group, whereas the correlations between the AP ratio and other biometric parameters in the M-LVC group were strong, especially in the anterior corneal radius (p < 0.001, r = 0.656), AL (p < 0.001, r = 0.523), keratometry (p < 0.001, r = -0.656), and TK (p < 0.001, r = − 0.715).
Comparison of prediction errors among three IOL power formulas in eyes with previous M-LVC according to AL
For analysis of patients with a history of M-LVC who underwent cataract surgery, 39 eyes of 31 patients (11 men, 20 women) were enrolled (Table 2). The mean AL and AP ratio were 27.73 ± 2.39 mm and 1.24 ± 0.07, respectively. We classified the eyes into three subgroups by AL: Group A (AL < 26.0 mm), Group B (26.0 mm\(\le\)AL < 28.0 mm), and Group C (28.0 mm \(\le\)AL). The mean AP ratios were 1.21 ± 0.05, 1.22 ± 0.02, and 1.28 ± 0.09 in Groups A, B, and C, respectively. Table 3 shows the mean APE (MAE), median APE (MedAE), and percentage of prediction error within ± 0.5 D and ± 1.0 D of three IOL power calculation formulas (Haigis-L, Barrett True-K, and Barrett True-TK) for subgroups according to AL. In the case of Group A, no significant difference was found between the MedAEs of each formula. For Groups B and C, Haigis-L had significantly higher MedAE than Barrett True-TK (p = 0.014 and p = 0.04, respectively, Friedman test with Bonferroni post-hoc correction). In Group B, the percentage of prediction error within ± 1.0 D was significantly lower in Haigis-L (30.8%) than in Barrett True-K (84.6%) and Barrett True-TK (92.3%; p = 0.048 and p = 0.024, respectively; Cochran Q test with a Bonferroni correction). The distribution of the APE for each subgroup is shown in Fig. 2.
Table 2
Patient Demographics and Ocular Biometric Parameters on 39 Eyes with Cataract Surgery after Myopic Laser Vision Correction According to Axial Length.
| Total | Group A AL < 26.0 mm | Group B 26.0 mm ≤ AL < 28.0 mm | Group C 28.0 mm ≤ AL | P-value |
Eyes | 39 | 10 | 13 | 16 | |
Age (years) | 61.46 ± 7.58 | 61.1 ± 8.71 | 62.53 ± 6.23 | 60.81 ± 8.22 | 0.82 |
Ant. corneal radius (mm) | 8.59 ± 0.54 | 8.03 ± 0.28 | 8.57 ± 0.25 | 8.95 ± 0.54 | < 0.001 |
Post. corneal radius (mm) | 6.89 ± 0.29 | 6.64 ± 0.19 | 6.98 ± 0.19 | 6.98 ± 0.33 | 0.01 |
AP ratio | 1.24 ± 0.07 | 1.21 ± 0.05 | 1.22 ± 0.02 | 1.28 ± 0.09 | 0.02 |
CCT (mm) | 0.49 ± 0.04 | 0.52 ± 0.06 | 0.47 ± 0.03 | 0.49 ± 0.03 | 0.07 |
AL (mm) | 27.73 ± 2.39 | 25.10 ± 0.75 | 26.94 ± 0.55 | 30.02 ± 1.78 | < 0.001 |
ACD (mm) | 3.35 ± 0.26 | 3.27 ± 0.36 | 3.31 ± 0.20 | 3.44 ± 0.22 | 0.22 |
Keratometry (D) | 39.37 ± 2.47 | 42.05 ± 1.54 | 39.39 ± 1.11 | 37.67 ± 2.28 | < 0.001 |
Total keratometry (D) | 38.83 ± 2.69 | 41.67 ± 1.75 | 38.93 ± 1.17 | 36.97 ± 2.52 | < 0.001 |
Values are presented as mean ± standard deviation. AP, anterior-posterior; CCT, central corneal thickness; AL, axial length; ACD, anterior chamber depth |
Statistical significance was defined as p < 0.05. |
Table 3
Median and Mean Absolute Prediction Errors and Percentage of Prediction Error within ± 0.5 D and ± 1 D of Three Intraocular Lens Power Calculation Formulas in Subgroups Classified by Axial Length
| Haigis-L | Barrett True-K | Barrett True-TK | P-value |
Group A (AL < 26.0 mm, n = 10) |
MedAE (MAE) | 0.62 (0.51 ± 0.33) | 0.32 (0.37 ± 0.21) | 0.25 (0.31 ± 0.18) | 0.14 |
Within ± 0.5 D | 50% | 80% | 70% | 0.09 |
Within ± 1 D | 100% | 100% | 100% | > 0.99 |
Group B (26.0 mm ≤ AL < 28.0 mm, n = 13) |
MedAE (MAE) | 1.06 (1.00 ± 0.40) | 0.73 (0.74 ± 0.49) | 0.57 (0.64 ± 0.46) | 0.017* |
Within ± 0.5 D | 7.7% | 23.1% | 30.8% | 0.17 |
Within ± 1 D | 30.8% | 84.6% | 92.3% | 0.001† |
Group C (28.0 mm ≤ AL, n = 16) |
MedAE (MAE) | 1.09 (1.15 ± 0.78) | 0.99 (1.02 ± 0.73) | 0.87 (0.96 ± 0.66) | 0.04‡ |
Within ± 0.5 D | 31.3% | 31.3% | 31.3% | > 0.99 |
Within ± 1 D | 43.8% | 50% | 50% | 0.77 |
Values are presented as mean ± standard deviation. |
*Haigis-L and Barrett True-TK: p = 0.014 using the Friedman test with Bonferroni post-hoc correction |
†Haigis-L and Barrett True-K: p = 0.048, Haigis-L and Barrett True-TK: p = 0.024 using the Cochran Q test with a Bonferroni correction |
‡Haigis-L and Barrett True-TK: p = 0.04 using the Friedman test with Bonferroni post-hoc correction |
Statistical significance was defined as p < 0.05. |
AL, axial length; MAE, mean absolute prediction error; MedAE, median absolute prediction error; TK, total keratometry |
In linear regression analyses of the relationship between the AP ratio and APE of three IOL power formulas, no correlation between the AP ratio and APE was statistically significant (p = 0.06, 0.94, and 0.11 for Haigis-L, Barrett True-K, and Barrett True-TK, respectively). The APEs of Haigis-L and Barrett True-TK tended to increase as the AP ratio increased, whereas the APE of Barrett True-K tended to decrease slightly as the AP ratio increased.