A total of 89 eyes (63 patients) were included and randomized into the CTR (A-CTR) and control groups (B-CON). The mean age was 55.93 ± 10.17 years (range 35 to 82 years), and preoperative mean AL in all eyes was 30.30 ± 2.18 mm (range 27.05 to 35.75 mm), and preoperative mean ACD was 3.43 ± 0.35 mm (range 2.71 to 4.81 mm). Table 1 shows the baseline characteristics of the patients. There were no statistically significant between group differences in age, AL, ACD, or CDVA 1 month post-surgery.
Table 1
Baseline characteristics of patients.
Parameter | A-CTR | B-CON | t/z | p |
n | 43 | 46 | - | - |
Sex | Male | 14(32.6%) | 18(39.1%) | - | - |
Female | 29(67.4%) | 28(60.9%) | - | - |
Age(yr) | 55.26 ± 9.62 | 56.57 ± 10.72 | -0.61 | 0.55 |
AL(mm) | 30.36(28.33, 32.42) | 30.10(28.33, 31.97) | 0.63 | 0.53 |
ACD(mm) | 3.42 ± 0.31 | 3.44 ± 0.40 | -0.24 | 0.81 |
Postop CDVA (logMAR) | 0.21 ± 0.13 | 0.21 ± 0.19 | -0.29 | 0.83 |
ACD = anterior chamber depth; AL = axial length; CDVA = corrected distance visual acuity; IOL = intracocular lens; logMAR = logarithm of the minimum angle of resolution; |
CTR = capsular tension ring group; CON = control group.
*Statistically significant
Comparison of refraction at different postoperative times of the A-CTR group showed no statistical difference (P = 0.07, P = 0.82, P = 0.83), indicating that the refraction of patients with CTR implantation tended to be stable 1 week post-surgery. Comparison of refraction at 1 week and 1 month, 1 week and 3 months post-surgery of B-CON group showed statistical difference (P < 0.001). There was no statistical difference between 1 month and 3 months post-surgery (P = 0.45), indicating that the refraction of the control group tended to be stable 1 month post-surgery (Table 2).
Table 2
Comparison of refractive at different time after surgery (D).
Parameter | A-CTR (n = 43) | B-CON (n = 46) |
After 1 week(D) | -2.72 ± 0.62 | -2.59 ± 0.74 |
After 1 month(D) | -2.71 ± 0.66 | -2.46 ± 0.68 |
After 3 months(D) Pa Pb Pc | -2.70 ± 0.66 0.70 0.82 0.83 | -2.43 ± 0.71 < 0.001* < 0.001* 0.45 |
CTR = capsular tension ring group, CON = control group.
aThe refractive at 1 week and 1 month after surgery were compared by independent sample t test; bThe refractive at 1 week and 3 months after surgery were compared by independent sample t test; cThe refractive at 1 month and 3 months after surgery were compared by independent sample t test.
*Statistically significant
The changes of ACD in the A-CTR and B-CON groups at 1 week, 1 month, and 3 months post-surgery were compared, respectively (Table 3). The Master 700 was affected by the anterior optical surface of IOL when measuring postoperative ACD, and the repeated measurement of ACD was not detected in some patients. Therefore, the patients without ACD measurement were excluded. A total of 45 eyes with ACD before operation, 1 week, 1 month, and 3 months post-surgery were continuously measured, including 21 eyes in the A-CTR group and 24 eyes in the B-CON group.
Table 3
Comparison of ACD at different time after surgery (mm).
Parameter | A-CTR (n = 21) | B-CON (n = 24) |
After 1 week(mm) | 4.75 ± 0.28 | 5.00 ± 0.38 |
After 1 month(mm) | 4.82 ± 0.52 | 4.91 ± 0.40 |
After 3 months(mm) Pa Pb Pc | 4.87 ± 0.47 0.36 0.11 0.55 | 4.86 ± 0.39 0.12 0.11 0.41 |
CTR = capsular tension ring group, CON = control group.
aThe ACD at 1 week and 1 month after surgery were compared by independent sample t test; bThe ACD at 1 week and 3 months after surgery were compared by independent sample t test; cThe ACD at 1 month and 3 months after surgery were compared by independent sample t test.
Evidently, the ACD in the A-CTR group gradually deepened and that in the B-CON group gradually shallowed. However, there was no statistical difference in the ACD between the two groups at each time post-surgery (P > 0.05).
The refraction of all patients tended to be stable at 1 month post-surgery. Therefore, the refractive outcomes of patients at 1 month post-surgery were selected and compared with the refraction predicted by the seven formulas to calculate the PE and the AE of the seven formulas were further compared.
The Kruskal–Wallis rank sum test confirmed statistical differences between the AE for the various formulas in the A-CTR and B-CON groups, respectively (P < 0.001). Therefore, the difference between the two groups is further analyzed (Table 4). In the A-CTR group, the Holladay II formula differed significantly from Hill-RBF 2.0, EVO, and Kane formulas. However, there was no statistical significance among the other formulas. In the B-CON group, Holladay II formula was statistically significantly different from BU II, Hill-RBF 2.0, EVO, Kane, and Haigis formulas. While there was a statistically significant difference in SRK/T formula compared to Hill-RBF 2.0 and EVO formulas, there were no statistical significances among other formulas.
Table 4
Pairwise comparison of AE values of 7 formulas in A-CTR group and B-CON group.
formula | A-CTR n = 43 P | B-CON n = 46 P |
EVO∼Hill-RBF 2.0 | 1.00 | 1.00 |
EVO∼BU II | 1.00 | 1.00 |
EVO∼Kane | 1.00 | 1.00 |
EVO∼Haigis | 0.93 | 0.09 |
EVO∼SRK༏T | 0.21 | <0.001* |
EVO∼Holladay II | <0.001* | <0.001* |
Hill-RBF 2.0∼BU II | 1.00 | 1.00 |
Hill-RBF 2.0∼Kane | 1.00 | 1.00 |
Hill-RBF 2.0∼Haigis | 1.00 | 0.97 |
Hill-RBF 2.0∼SRK༏T | 0.31 | 0.02* |
Hill-RBF 2.0∼Holladay II | 0.01* | <0.001* |
BU II∼Kane | 1.00 | 1.00 |
BU II∼Haigis | 1.00 | 1.00 |
BU II∼SRK༏T | 1.00 | 0.12 |
BU II∼Holladay II | 0.09 | <0.001* |
Kane∼Haigis | 0.51 | 1.00 |
Kane∼SRK༏T | 0.11 | 0.33 |
Kane∼Holladay II | <0.001* | <0.001* |
Haigis∼SRK༏T | 1.00 | 1.00 |
Haigis∼Holladay II | 1.00 | 0.03* |
SRK༏T∼Holladay II | 1.00 | 1.00 |
BU II = Barrett Universal II; EVO = Emmetropia Verifying Optical; Mann-Whitney-U Test *Statistically significant |
Figures 1 and Figs. 2 show the AE distribution of the A-CTR and B-CON groups at 1-month post-surgery, respectively. In the A-CTR group, the median AE of Kane formula was the smallest, in the B-CON group, the median AE of the EVO formula was the smallest. However, when Kane and EVO were compared in the same group, there was no statistical significance (P = 1.0).
The percentages of AE for the seven formulas within ± 0.5D, ± 1.0D, ± 1.5D, and ± 2.0D in the A-CTR and B-CON groups at 1 month post-surgery were described. Figure 3 shows that the proportion of AE in the A-CTR group in ± 0.5D is Kane > EVO > Hill-RBF 2.0 > BU II > SRK/T > Haigis > Holladay II. Figure 4 shows that the proportion of AE in the B-CON group in ± 0.5D is EVO > Hill-RBF 2.0 > Kane > BU II > Haigis > SRK/T > Holladay II.
The PE of the same formula was compared between the A-CTR and B-CON groups, and the effect of CTR implantation on the prediction accuracy of the seven formulas was studied (Fig. 5, Table 5). The PE of Hill-RBF 2.0 and EVO formulas in the A-CTR group was more hyperopic than in the B-CON group. However, there was no significant difference between the two groups (P = 0.11, P = 0.10). The PE of the other five formulas was more myopic in the A-CTR group than in the B-CON group. There was no significant difference in the PE of the five formulas between the two groups (P = 0.41, P = 0.50, P = 0.25, P = 0.33, P = 0.74). The results indicated that CTR implantation could affect the PE of the formula, and the deviation of myopia or hyperopia was not statistically significant. Therefore, CTR implantation had no clinically significant effect on the prediction accuracy of the seven calculation formulas.
Table 5
PE of the same formula after surgery were compared between the two groups.
Parameter | Group | Mean ± SD | MNE (95% CI) | T-test |
t/z | P |
SRK/T | A-CTR | -0.53 ± 0.74 | 0.14 (-0.40-0.16) | -0.83 | 0.41 |
B-CON | -0.42 ± 0.59 |
Holladay II | A-CTR | -0.83 ± 0.70 | 0.14 (-0.38-0.19) | -0.67 | 0.50 |
B-CON | -0.73 ± 0.64 |
Haigis | A-CTR | -0.45 ± 0.67 | 0.13 (-0.42-0.11) | -1.15 | 0.25 |
B-CON | -0.29 ± 0.59 |
BU II | A-CTR | -0.13 ± 0.49 | 0.11 (-0.11-0.32) | 0.99 | 0.33 |
B-CON | -0.23 ± 0.51 |
Hill-RBF 2.0 | A-CTR | -0.03 ± 0.46 | 0.11 (-0.04-0.40) | 1.62 | 0.11 |
B-CON | -0.20 ± 0.55 |
EVO | A-CTR | 0.05 ± 0.42 | 0.09 (-0.09-0.28) | 1.04 | 0.10 |
B-CON | -0.05 ± 0.45 |
Kane | A-CTR | 0.10 ± 0.39 | 0.10 (-0.23-0.16) | -0.33 | 0.74 |
B-CON | 0.14 ± 0.51 |
BU II = Barrett Universal II; EVO = Emmetropia Verifying Optical; |
CTR = capsular tension ring group; CON = control group; CI = confidence interval |