Over the last decade and a half, clinicians have used a range of nomograms—DONO (Donnenfeld nomogram),1 NOMO (Nichamin Age and Pachymetry Adjusted nomogram),2 and others—to optimize predictability with both manual and laser-assisted correction.
However, in the summer of 2020, refractive surgeons gained an impressive new tool with The Wörtz-Gupta™ LRI Calculator, which I consider one of the most valuable innovations for lens-based refractive surgery in recent years.
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The Wörtz-Gupta LRI calculator
First introduced by Gary Wörtz, MD, and Preeya K. Gupta, MD, in a paper they co-authored, “Outcomes of Femtosecond Laser Arcuate Incisions in the Treatment of Low Corneal Astigmatism,” the Wörtz-Gupta limbal relaxing incisions (LRI) calculator provides a formula to attain accurate, individualized measurements to be used in femtosecond laser-assisted arcuate incisions for the treatment of astigmatism.3
With 224 patients as the study population, the breakdown was an almost even split between the control (n=100) and treatment (n=124) groups based on the average pre-operative cylinder measurements.
The surgeons set out to answer two questions:
- Does uncorrected low corneal astigmatism (between 0.25 to 1D [diopter]) impact uncorrected visual acuity (UCVA) outcomes after cataract surgery?
- Can a femtosecond laser be used to effectively treat low levels of astigmatism?
The answer to both was a resounding “yes.” The astigmatic patients treated with femtosecond laser arcuate incisions were 1.8 times more likely to have 20/20 UCVA after cataract surgery. With regard to achieving 20/25 UCVA or better, the increase was 3.5 times. In addition, within the laser arcuate treatment group, there was a statistically significant increase post-operatively in patients with ≤0.5D of astigmatism, which accounted for 89% of those patients.3
My experience with the Wörtz-Gupta formula
My surgical experience echoes their findings. Within our practice, I am not only a clinician and surgeon, but also serve as research director and biometrist. And, for me, femtosecond lasers have done the best job to date of simplifying the process of placing arcuate incisions using one’s individualized nomogram.
The Wörtz-Gupta nomogram employs a 9mm optical zone with 80% depth on the steep axis, with all primary wound incisions being performed temporally on the 180-degree meridian, approximately. After entering the patient information, the LRI calculator provides a personalized diagram to be used during the planning and procedure.
Our practice implemented the Wörtz-Gupta LRI calculator with stellar results. We have discovered that for 1.2 to 1.25D of astigmatism (both with and against the rule), our ability to achieve 20/20 UCVA post-cataract surgery has increased by nearly two times. Also, in these patients, as opposed to those whose astigmatism is not being corrected at the time of surgery, we are far more likely to achieve less than 0.25D of cylinder. With the traditional gold-standard benchmark being 0.5D or less, we are thrilled to see this twofold improvement.
I would be remiss not to mention the convenience factor. Having the LRI calculator online at our fingertips (www.LRIcalc.com) has made calculating astigmatism correction incredibly easy. It can even be accessed in the operating room at the time of surgery and applied immediately.
In conclusion
Having a free, online, evidence-based nomogram that clinicians can seamlessly implement into their practice is revolutionary for refractive surgeons. After entering the required data, the formula generates the precise and individualized measurements to help you potentially achieve premium visual outcomes for low-level astigmatism patients.
If you have not utilized the Wörtz-Gupta LRI calculator, I would encourage you to take advantage of this groundbreaking software.
Disclaimer: The Wörtz-Gupta™ Formula (patent pending) femtosecond laser arcuate incision calculator is meant to serve as an adjunct tool to assist physicians in the correction of astigmatism in conjunction with the intraocular lens (IOL) placement. The information contained herein is derived from the work and nomogram(s) of Gary Wörtz, MD, and Preeya K. Gupta, MD. The medical opinions and views expressed in the Calculator are those of Drs. Wörtz and Gupta and not those of any manufacturer of femtosecond lasers.
