For nearly 20 years I have used limbal relaxing incisions (LRIs) to correct astigmatism at the time of cataract surgery. Initially, it was because early multifocal IOLs did not incorporate toric correction. But even now that multifocal toric lenses are available, I still find myself using LRIs for a wider range of patients. As little as 0.50 to 0.75 D of residual astigmatism is enough to affect UCVA and compromise the quality of vision patients expect after modern cataract surgery (1).

The prevalence of clinically significant corneal astigmatism in the general population is substantial. Studies estimate approximately 40% to 50% of patients presenting for cataract surgery have 1.00 D or more of corneal astigmatism (2), while another large segment has between 0.25 and 1.25 D (2-4). Addressing astigmatism at the time of surgery rather than with spectacles has become a defining feature of modern refractive cataract surgery.

My approach to LRIs has evolved in parallel with the technology available. I began with manual incisions guided by published nomograms, progressed to image-guided systems that projected the LRI arc onto the cornea using biometric measurements, and ultimately transitioned to laser-assisted LRIs. Each step has brought greater precision, better automation, and, most importantly, more consistent outcomes for my cataract patients.

The limitations of a manual LRI technique

Manual LRIs are a well-established technique with a strong safety profile and decades of supporting data (see sidebar LRIs: Supporting Data) (5-7). When performed with a reproducible technique and an appropriate nomogram, they can reliably reduce mild to moderate astigmatism. However, their accuracy depends on a chain of steps that each introduce potential for error.

The process begins with marking the eye in the preoperative area. With the patient seated upright, a surgeon or technician marks the horizontal 0° to 180° axis to serve as a reference for subsequent intraoperative markings. This step is more erroneous than it may appear. Patient positioning, parallax, and the inherent imprecision of an ink-based corneal marking technique all introduce variability into the meridional reference (8). Any deviation in the initial mark propagates directly to the placement of the LRI arc. If off by even a few degrees, the incision is placed on the wrong meridian. According to the literature, a 10º axis error reduces astigmatic correction by approximately 34% (9).

In addition to axis accuracy, manual LRIs require a surgeon to independently calculate nomogram parameters, input data, confirm incision depth settings, and mark the cornea intraoperatively. Each manual step carries a potential for transcription and execution errors. As with any process involving multiple sequential manual inputs, there is cumulative risk of small errors affecting outcomes.

A more precise technique

Laser technology addresses the core limitations of manual LRIs by creating reproducible, computer-controlled intrastromal incisions with precise arc length, depth, angular position, and optical zone (Figure 1) (10). Several platforms, including the ALLY Robotic Cataract Laser System (LENSAR), Catalys Precision Laser System (Johnson & Johnson Vision), LenSx Laser System (Alcon), and Victus Femtosecond Laser Platform (Bausch + Lomb), incorporate LRI capability into femtosecond laser-assisted cataract surgery (FLACS) workflows, enabling astigmatism treatment and cataract surgery in a single integrated session.

Integration of preoperative biometric data from topography directly into the treatment planning interface is not uniformly available across all platforms, but it is available with ALLY. Iris registration is used to precisely align the astigmatism axis at the time of treatment, resulting in automatic cyclotorsion compensation. Studies indicate even 6º of cyclotorsion may undermine astigmatic correction if not accounted for (9). The planning screen then applies an integrated nomogram to calculate arc parameters, accounting for factors including patient age, the orientation of astigmatism (with-the-rule vs against-the-rule), and the contribution of the cataract incision to surgically induced astigmatism (SIA). Once measurements are confirmed and the treatment plan approved, the laser creates the incisions, which may then be opened by a surgeon under the operating microscope.

The incisional design may also contribute to long-term outcomes. Whereas manual LRIs and even some femtosecond LRIs are perpendicular, ALLY creates beveled incisions. This architecture is thought to promote greater corneal biomechanical stability and reduce the risk of wound gaping or epithelial plugging versus a perpendicular cut. In a retrospective analysis of 22 patients who received beveled arcuate incisions, there was no statistically significant regression in astigmatic correction between the early postoperative period and 36 months, supporting the durability of the incision design over time (11).

In my experience, the workflow efficiency gains are meaningful. Integrating biometry data directly into the planning screen and automating parameter calculations has eliminated a multitude of manual data-entry steps that slow conventional workflows and introduce transcription risk. My staff and I both benefit from the time savings, and a more streamlined process contributes to a more consistent surgical experience.

Navigating the learning curve

When I adopted image-guided LRI technology, the main learning curve centered on obtaining reliable captures to ensure measurements were consistent before creating the incisions. The process required time and repetition to build confidence in the device.

With ALLY, the transition was more straightforward. The biometric data flows directly into the planning interface and the nomogram calculations are automated. The treatment planning step itself therefore is intuitive once a surgeon learns the steps on the planning screen. There is, of course, a learning curve associated with the physical aspects of docking the patient and running the laser system, but the treatment logic is built in. I simply confirm the measurements and proposed parameters align with my clinical judgment.

The shift from manual calculations to an automated, integrated workflow has reduced the human factors that influence my patients’ outcomes. By removing the need to manually input data, set depth values, and verify nomogram outputs independently, the system reduces the opportunity for compounding errors that accumulate across sequential manual steps.

Evaluating performance: Refractive outcomes and vector analysis

I recently conducted a retrospective analysis to evaluate the performance of my laser LRI approach. Preoperative biometric measurements were obtained for 29 eyes. All eyes received a standard (ie, nontoric) monofocal IOL, and those with prior LASIK or other corneal refractive surgery were excluded from the analysis. The treated astigmatism ranged from approximately 0.75 to 1.25 D. I used a modified Nichamin-Woodcock nomogram developed by Denise Visco, MD (12).

Postoperative refractive accuracy (Figure 2) compared favorably with published benchmarks for femtosecond laser arcuate keratotomy. In a study of 189 eyes that underwent femtosecond-assisted arcuate keratotomy at the time of cataract surgery 95.8% achieved ≤0.50 D of postoperative refractive astigmatism (12). In a two-year follow-up analysis of 266 eyes undergoing femtosecond laser-assisted arcuate keratotomy with FLACS, outcomes showed sustained stability of astigmatic correction over time with minimal regression (13).

A vector analysis of my series, accounting for both the magnitude and axis of the induced astigmatic change, provided a multidimensional picture of how well the treatment matched the intended correction, confirming a meaningful reduction in mean astigmatism and reduced dispersion consistent with accurate incision placement and effective performance of the applied nomogram (Figure 3). The correction index, which relates SIA to target-induced astigmatism (TIA), was at or near 1.0. This result indicated neither systematic undercorrection nor overcorrection occurred, indicating no nomogram adjustment was necessary. The built-in parameters accounted for the relevant patient variables, including age, astigmatism orientation, and the SIA contribution of the cataract incision, without requiring customization in this cohort.

Patient selection and clinical decision making

When I first started using femtosecond LRIs, I was cautious about offering patients a meaningful reduction in low to moderate astigmatism without also recommending a toric IOL. With the precision of modern laser LRIs and the confidence my outcomes now provide, I am more comfortable discussing the potential for UCVA improvement in a broader range of patients. One population where I now feel particularly confident is those with mild to moderate astigmatism (0.75  to 1.25 D). Historically, this was a gray zone where the choice between a toric IOL and an incision-based approach required careful consideration of clinical and practical factors. Toric IOLs remain the gold standard for higher levels of astigmatism and offer excellent predictability across a broad range. Studies show more than 77% of eyes achieve ≤0.50 D of residual astigmatism (14). But for patients at the lower end of the treatable range, a well-executed femtosecond laser LRI is not a concession but rather a well-matched tool. A platform that offers iris registration and an integrated nomogram means I can offer patients clinically meaningful and predictable reduction in refractive cylinder, preserved corneal anatomy, and no additional premium IOL cost to navigate. Although the last point matters to many patients, it is not the reason I reach for LRIs first in this population. It is because my outcomes support it.

Laser LRIs are therefore a great option for patients who have higher preoperative astigmatism (1.50 to 2.00 D) but prefer to avoid the additional out-of-pocket cost of a toric IOL. For these patients, I have a candid conversation about what laser LRIs can and cannot accomplish. In my experience they can typically reduce astigmatism by 50% to 75%, which may not eliminate the need for glasses entirely but can significantly reduce the degree of dependence. Patients who understand this expectation are generally very satisfied with their outcomes. Even a substantial reduction in residual astigmatism may translate into meaningfully improved UCVA and quality of vision for everyday tasks.

For straightforward cases of regular corneal astigmatism in the absence of prior corneal surgery, laser LRIs provide an effective, well-integrated option that supports the goals of refractive cataract surgery. Patients with a history of prior corneal refractive surgery, irregular astigmatism, and corneal ectasia, however, are not candidates for LRI-based correction and require individualized management.

Consider the advantages

For surgeons considering the transition from manual to laser-assisted LRIs, consider the following questions:

• How reliably are you hitting your astigmatic targets with your current technique?

• How often do you need to perform enhancement procedures for patients due to under- or overcorrection?

• How much of your time and your team's time is consumed by the manual steps that modern platforms can automate?

In my view, LRIs have always been an option for the correction of astigmatism at the time of cataract surgery. With femtosecond laser platforms now supported by iris registration and integrated nomograms, I believe we can offer more patients a genuinely refractive outcome conversation at the time of cataract surgery. My early outcomes confirm that precise, reproducible astigmatic correction is achievable within a routine cataract surgery workflow. More importantly, they have changed the conversations I have with patients and expanded the population I can serve with a refractive mindset.