Impact of ICL Fixation Direction on Postoperative Vault and Prediction Accuracy Using the KS Formula

Area of Science:

• Ophthalmology
• Refractive Surgery
• Implantable Collamer Lens (ICL) Technology

Background:

• The Implantable Collamer Lens (ICL) is a widely used refractive surgery option for correcting myopia.
• Accurate ICL sizing and optimal lens positioning are critical for achieving desired visual outcomes and minimizing complications.
• The KS formula is a common method for determining ICL size, but fixation orientation's impact on vault is less understood.

Purpose of the Study:

• To compare postoperative vault measurements between horizontal and vertical fixation of the Implantable Collamer Lens (ICL).
• To evaluate the influence of fixation orientation on ICL size determined by the KS formula.
• To assess the impact of fixation on prediction error and vault accuracy in myopic ICL implantation.

Main Methods:

• Retrospective analysis of 2,343 eyes from 1,275 patients undergoing myopic ICL implantation.
• Pre-operative anterior segment optical coherence tomography (AS-OCT) performed in horizontal and vertical orientations.
• Comparison of postoperative vault measurements between horizontal and vertical fixation groups using KS formula-derived ICL sizes.

Main Results:

• Horizontal fixation resulted in a significantly larger mean postoperative vault (0.50 ± 0.20 mm) compared to vertical fixation (0.43 ± 0.17 mm).
• A higher proportion of eyes with excessively large vaults (⩾ 1 mm) were observed in the horizontal fixation group (0.85%) versus the vertical group (0.13%).
• Prediction error and median absolute error were significantly greater in the horizontal fixation group, indicating lower prediction accuracy.

Conclusions:

• Horizontal ICL fixation, when sized with the KS formula, leads to a larger postoperative vault and reduced prediction accuracy compared to vertical fixation.
• Vertical fixation appears to be a safer and more predictable method for ICL implantation, potentially minimizing vault-related complications.
• These findings suggest that optimizing ICL fixation orientation is crucial for achieving predictable refractive outcomes.