Prospective Randomized Intraindividual Comparison Between Digital And Manual Axis Marking For Correction Of Myopic Astigmatism With Toric Phakic Intraocular Lenses.

Refractive errors such as myopia, hyperopia, and astigmatism can be permanently corrected through surgical interventions. In cases where keratorefractive laser treatment is not feasible, phakic intraocular lenses (pIOLs) can be implanted. Toric pIOLs require precise alignment to achieve optimal astigmatic correction. This study aims to compare the outcomes of digital axis marking with the Callisto Eye System to manual axis marking for toric phakic IOL implantation, focusing on visual and refractive results, as well as the stability of pIOL rotation.

The study was conducted at the Department of Ophthalmology, University of Graz, Austria.

This prospective, randomized, controlled, intraindividual study includes 20 patients aged 20 to 60 years with significant refractive astigmatism (≥0.5 D) scheduled for ICL implantation. The study comprises two groups, differing in the sequence of axis marking: ICL implantation using digital marking via the surgical microscope (Callisto Eye System) or manual axis marking using a sterile syringe for horizontal corneal scratches at the upright sitting patient and intraoperative alignment with a Mendez ring. The postoperative evaluations of axis alignment took place at the 3-month follow-up based on retroillumination photography.

The mean alignment error after digital marking was 2.8±3.1° (range: 0 to 10), and 4.4±5.1° (range: 0 to 19) following manual marking (p=0.292). The gain in best-corrected visual acuity following surgery was logMAR -0.06±0.07 (range: 0.1 to -0.1) following digital marking, and logMAR -0.07±0.07 (range: 0.1 to -0.2) in manual marking (p=0.812). The residual refractive error after digital marking was spherical equivalent (SE) -0.01±0.08 D (range: -0.25 to +0.25), and after manual marking SE -0.03±0.09 D (range: 0.0 to +0.25) (p=0.233). The remaining refractive astigmatism was 0.06±0.20 D (range: 0.0 to 0.75) with digital marking and 0.05±0.15 D (range: 0.0 to 0.5) with manual marking (p=0.824). All surgeries remained uneventful.

This study could show that digital axis marking and manual axis marking were comparable in terms of postoperative axis alignment error as well as visual and refractive outcomes.