Published in Refractive Surgery

How to Use the LRI Calculator

Gary Wörtz, MD

Gary Wörtz, MD

Preeya K. Gupta, MD

Preeya K. Gupta, MD

This is editorially independent content
4 min read
Drs. Gupta and Wörtz discuss how ophthalmologists can utilize LRICalc.com, with its LRI calculator for limbal relaxing incisions (LRIs).
It has been said, “Necessity is the mother of invention.” This is true of LRICalc.com.
As the widely used Donnenfeld nomogram was developed specifically for manual incisions, Preeya K. Gupta, MD, and Gary Wörtz, MD, realized the field could benefit from a formula—specifically designed for arcuate incisions made with a femtosecond laser—to obtain precise, individualized measurements and placement for limbal relaxing incisions (LRIs).
Interventional Mindset is an educational series that gives eye physicians the needed knowledge, edge, and confidence in mastering new technology to grow their practices and provide the highest level of patient care. Our focus is to reduce frustrations associated with adopting new technology by building confidence in your skills to drive transformation.
Browse through our videos on a variety of topics within cataract and refractive surgery, glaucoma, and ocular surface disease to learn practical insights into adopting a variety of new surgical techniques and technology.

The development of the Wörtz-Gupta Formula

Thus, Arcuate Innovations, with its revolutionary Wörtz-Gupta Formula and associated femtosecond laser LRI Calculator, was born. The formula and findings are highlighted in their paper “Outcomes of Femtosecond Laser Arcuate Incisions in the Treatment of Low Corneal Astigmatism.”
To summarize, the study analyzed the real-world outcomes of 224 patients (124 study eyes, 100 control eyes) in regard to the management of low-level astigmatism of 1D or less with corneal arcuate incisions performed with a femtosecond laser during cataract surgery.1
It was determined that patients who had femtosecond laser-assisted cataract surgery (FLACS) with arcuate incisions were 1.8 times more likely to achieve 20/20 uncorrected visual acuity (UCVA) or better and 3.54 times more likely to achieve 20/25 UCVA or better.1

Key principles of the Wörtz-Gupta formula and calculator

This straightforward formula applies four primary principles.
The Wörtz-Gupta LRI calculator is designed:
  1. For arcuate incisions with a femtosecond laser.
  2. To treat low levels of corneal astigmatism; the calculator will lock out at values above 1.25D diopters of astigmatism.
  3. With the intention that incisions be opened and irrigated.
  4. For incisions to be placed at the 9mm optical zone at 80% depth.
Taking into consideration the amount of posterior corneal astigmatism and the low level of surgically-induced astigmatism (SIA) encountered by most surgeons, the creators also baked these factors into the formula. In addition, they accounted for the fact that most surgeons approach cataract surgery temporally.
Note: Through studies and personal practice, both surgeons have discovered that, for levels of astigmatism over 1.25D, toric intraocular lenses (IOLs) can be more effective.

Calculating with convenience

To ensure you can access these calculations straight from the operating room, there is a mobile version of the calculator for both iPhone- and Android-based smartphone operating systems, all available at www.LRIcalc.com.

The formula in action

When utilizing the Wörtz-Gupta Formula, it’s a simple plug-and-play process. Once the requested data has been inputted into the respective fields, the algorithm will supply individualized calculations.
After reading a short disclaimer and checking an acknowledgment, you will input the following information:
  • ID number—do not provide protected health information
  • Patient age
  • Right eye vs. left eye
  • Level of corneal astigmatism—this value must be 1.25D or below
  • Steep corneal axis, between 0° and 180°
Then, hit calculate. Along with a summary of the provided information, you will be given the degree of the phaco incision and lengths for Arc Length #1 and Arc Length #2.
Figure 1 below reveals the calculations for a 65-year-old patient with 1D of astigmatism and steep corneal axis of 90° in the right eye.
LRI Calculator Example
Figure 1: Courtesy of the authors.

A note on safety and size

Based on clinical experience and research while developing this formula, both surgeons found that incisions larger than 50° have an increased potential for corneal destabilization and related complications; therefore, there is never an option for an arc length larger than 50° in the online calculator.

In closing

Whether you're a new surgeon who is just finding their footing or a more experienced surgeon seeking a simplified solution to LRI calculations, the Wörtz-Gupta Formula can be beneficial.
Demonstrating the core value of an interventional mindset, the developers of LRICalc.com did so to help ophthalmologists of all skill levels potentially achieve better and more predictable results to optimize patient care.
Both surgeons welcome feedback from colleagues who have utilized the tool.
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 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.
  1. Wortz G, Gupta PK, Goernert P, et al. Outcomes of Femtosecond Laser Arcuate Incisions in the Treatment of Low Corneal Astigmatism. Clin Ophthalmol. 2020;14:2229-2236. doi:  https://doi.org/10.2147/OPTH.S264370
Gary Wörtz, MD
About Gary Wörtz, MD

Gary Wörtz, MD is a board-certified ophthalmologist from Lexington, KY specializing in cataract and refractive surgery.

Since completing his training in 2008, Dr. Wörtz has successfully performed thousands of cataract and laser procedures. He currently practices in Lexington at Commonwealth Eye Surgery. Dr. Wörtz became one of the first surgeons in Kentucky to perform laser refractive cataract surgery. He utilizes the latest technology both in and out of the operating room to help restore vision for cataract patients.

Dr. Wörtz enjoys innovation and teaching his techniques to others around the country. He has been a consulting speaker for Alcon, AMO, Bio-Tissue, TearLab, Carl Zeiss Meditech and Dialogue Medical. He has also been a principal investigator in multiple FDA pharmaceutical trials in the ophthalmic sector. He has given numerous lectures at both the American Academy of Ophthalmology and the American Society of Cataract and Refractive Surgeons annual meetings. He is also a frequent contributor to many trade journals such Cataract and Refractive Surgery Today, MillennialEye, Ophthalmology Times, and EyeWorld, and was recently named to the editorial board of Ocular Surgery News.


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Preeya K. Gupta, MD
About Preeya K. Gupta, MD

Dr. Gupta earned her medical degree at Northwestern University’s Feinberg School of Medicine in Chicago, and graduated with Alpha Omega Alpha honors. She fulfilled her residency in ophthalmology at Duke University Eye Center in Durham, North Carolina, where she earned the K. Alexander Dastgheib Surgical Excellence Award, and then completed a fellowship in Cornea and Refractive Surgery at Minnesota Eye Consultants in Minneapolis. She served on the faculty at Duke University Eye Center in Durham, North Carolina as a Tenured Associate Professor of Ophthalmology from 2011-2021.

Dr. Gupta has authored many articles in the peer-reviewed literature and serves as an invited reviewer to journals such as Ophthalmology, American Journal of Ophthalmology, and Journal of Refractive Surgery. She has also written several book chapters about corneal disease and ophthalmic surgery, as well as served as an editor of the well-known series, Curbside Consultation in Cataract Surgery. She also holds several editorial board positions.

Dr. Gupta serves as an elected member of the American Society of Cataract and Refractive Surgery (ASCRS) Refractive Surgery clinical committee, and is also is the Past-President of the Vanguard Ophthalmology Society. She gives presentations both nationally and internationally, and has been awarded the National Millennial Eye Outstanding Female in Ophthalmology Award, American Academy of Ophthalmology (AAO) Achievement Award, and selected to the Ophthalmologist Power List.

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