Robotic Marker for Toric IOL Alignment
Digital/robotic marking systems for toric IOL alignment provide superior accuracy compared to manual marking techniques, resulting in less postoperative lens misalignment and better achievement of target astigmatism correction. 1, 2
Evidence for Digital/Robotic Marking Systems
Alignment Accuracy
Digital marker systems (such as VERION) demonstrate significantly lower mean axis alignment error (2.6° ± 2.3°) compared to manual ink marking (6.4° ± 2.8°) at one month postoperatively (P=0.009). 1
A randomized trial showed mean postoperative toric IOL misalignment of 2.4° ± 1.96° with digital marking versus 4.33° ± 2.72° with manual marking (P=0.003). 2
The rate of misalignment ≤5° was 86% with digital marking compared to 63% with manual ink marking (P=0.05). 1
Refractive Outcomes
Digital marking resulted in significantly less deviation from targeted induced astigmatism (0.10 ± 0.08 D) compared to manual marking (0.20 ± 0.14 D) (P=0.001). 2
While mean residual astigmatism at one month showed no significant difference between groups (0.7 ± 0.4 D), the improved alignment accuracy with digital systems translates to more predictable outcomes. 1
Uncorrected distance visual acuity showed a trend toward better outcomes with digital marking (0.12 ± 0.12 logMAR) versus manual marking (0.18 ± 0.14 logMAR), though this did not reach statistical significance. 2
Context from Clinical Guidelines
The American Academy of Ophthalmology emphasizes that accurate toric IOL alignment is critical for optimal astigmatism correction. 3
Toric IOLs provide significantly lower residual astigmatism than non-toric IOLs, even when corneal relaxing incisions are used (Level I+ evidence, Good quality, Strong recommendation). 3
Intraoperative aberrometry can assist with toric IOL axis alignment, though guidelines note it is not clear that intraoperative aberrometry always improves outcomes. 3
Manual Marking Alternatives
For surgeons without access to digital systems, manual techniques remain viable options:
Traditional bubble markers and pendulum markers both produce approximately 3° of alignment error on average. 4
Modified techniques such as anterior stromal puncture with staining show median IOL misalignment of 3° with only 3.4% requiring redialing. 5
Novel slit lamp-based markers (STORM) offer hands-free, no-touch approaches that may improve accuracy over handheld devices. 6
Clinical Implications
The superior precision of digital/robotic marking systems directly impacts patient outcomes by reducing residual astigmatism and improving visual quality. 1, 2
Every 1° of toric IOL misalignment results in approximately 3.3% loss of cylindrical correction, making precise alignment critical for achieving emmetropia. 2
Digital systems provide the additional advantage of preoperative planning integration and intraoperative real-time guidance, reducing human error throughout the surgical process. 2
The improved reproducibility and consistency of digital marking makes outcomes more predictable across different surgeons and surgical settings. 1
Common Pitfalls to Avoid
Relying solely on manual marking when digital systems are available, as this introduces unnecessary alignment error that directly compromises astigmatism correction. 1, 2
Failing to account for cyclotorsion between preoperative marking and intraoperative positioning—digital systems automatically compensate for this, while manual marking does not. 2
Not verifying alignment accuracy intraoperatively, regardless of marking method used, as even small deviations significantly impact outcomes. 3