Abstract
BACKGROUND: To investigate the effect of ICL implantation orientation on the postoperative vault quantitatively. METHODS: A total of 3510 eyes from 2042 subjects who underwent ICL implantation between July 1, 2020, and June 30, 2023, were included in this self-controlled retrospective study. We selected all subjects with nonhorizontal placement in the second surgical eye and divided them into four groups: same-sized vertical placement (group A), larger-sized vertical placement (group B), same-sized oblique placement (group C), and larger-sized oblique placement (group D). The achieved and predicted vaults were compared in each group. RESULTS: A total of 126, 81, 82 and 11 subjects were included in groups A, B, C and D, respectively. The mean difference in vault between fellow eyes in groups A, B, C and D was − 284.79 ± 169.92 μm, 53.59 ± 136.06 μm, -107.30 ± 136.09 μm and 208.18 ± 118.64 μm, respectively, and all the differences were statistically significant (P < 0.001, P = 0.001, P < 0.001, P < 0.001). The mean differences between the achieved and predicted vaults of the horizontal-placement eyes in groups A, B, C and D were 23.14 ± 233.20 μm, -46.39 ± 189.22 μm, 9.45 ± 187.43 μm, and − 76.72 ± 165.68 μm, respectively, and for the nonhorizontal-placement eyes, the achieved vault of subjects in groups A, B, C and D were 294.59 ± 181.72 μm, 313.22 ± 226.52 μm, 110.02 ± 177.67 μm and 191.63 ± 257.78 μm lower than the predicted vault; all the differences were statistically significant (all P < 0.05). In groups A and C, the difference in vault between horizontal and nonhorizontal ICL placement was significantly correlated with the vault of the first surgical eye (P < 0.001). CONCLUSIONS: Vertical or oblique implantation can safely fine-tune vault without exchanging the lens, especially when the first-eye vault is excessive. These within-subject estimates provide immediately applicable guidance for intra-operative orientation selection.