Effect of corneal marking features on toric intraocular lens alignment

The purpose of this study was to investigate the relation of the corneal ink mark size, shape, and location with the corneal perimeter in terms of the corresponding corneal axis.

This study was designed both prospective experimental and literature search. Contact lenses were used to demonstrate the spreading effect of the surgical ink mark. Open-access published corneal images with corneal ink marks were reviewed. Mark size and perimeter of both contact lenses and corneal images were performed in Image J software.

Twenty contact lenses and 15 corneal images with 32 corneal marks, which were obtained from the literature, were included in the study. Mean degree corresponding to the ink size for the group 1 was 8.3° ± 1.2° (range 5.5-10.3), for group 2 was 11° ± 1.1° (range 8-12), for group 3 was 4.2° ± 0.7° (range 3.2-5.5), for group 4 was 4.2° ± 0.7° (range 3.2-5.5), and for group 5 was 6.3° ± 2.5° (range 2-11.5).

Theoretically, it is wise to target further located ink mark from central cornea based on the 360/2π × (r2 - r1)/(r1 × r2) × M formula. It has been experimentally shown that the smaller corneal perimeter and closer mark to the central cornea may lead the more significant deviation from the targeted axis. Preoperative manual corneal marking may be more responsible for residual astigmatism than it is thought.