Welcome to the LRI Calculator

Important Update: The LRI Calculator has been redesigned for improved usability and enhanced compatibility with the latest browsers.

Please be advised the site works best when viewed with the latest version of Chrome or Safari.

NOTE: In order to align with the most widely accepted published literature, "Against-the-Rule" is now defined as any Steep Meridian of 0 to 30 degrees or 150 to 180 degrees.

This calculator uses published and proven nomograms, from peer-reviewed literature, that are not proprietary to J&J Vision.

The limbal relaxing incision (LRI) calculator can assist you in preoperative planning for LRI procedures; however, it is not a substitute for appropriate medical education and training or for the exercise of independent medical judgement. You may input relevant patient information and print the resulting diagram to assist you in making your incision. Data input is not stored by J&J Vision and patient identifying information is not collected by J&J Vision. The LRI calculator is intended for use in the US only.

LRI CALCULATOR LICENSE AGREEMENT, TERMS OF USE AND PRIVACY POLICY

PLEASE READ THIS LRI CALCULATOR SOFTWARE LICENSE AGREEMENT (THIS "AGREEMENT") BY SCROLLING DOWN. THIS AGREEMENT IS A LEGAL AGREEMENT BETWEEN YOU ("LICENSEE") AND JOHNSON & JOHNSON SURGICAL VISION, INC. ("J&J VISION") AND GOVERNS ACCESS TO AND USE OF THE LRI CALCULATOR SOFTWARE (THE “CALCULATOR”). BY CHOOSING "ACCEPT" ON THIS SCREEN, LICENSEE AGREES TO ALL OF THE TERMS STATED HEREIN AS WELL AS J&J VISION’S PRIVACY POLICY or TERMS OF USE, WHICH GOVERN ALL ASPECTS OF LICENSEE’S ACCESS TO AND USE OF THIS CALCULATOR.

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The Calculator contains technical information about the use of limbal relaxing incisions (LRIs) for correction of astigmatism in conjunction with intraocular lens (IOL) placement and is intended for use by physicians only. The information contained herein is derived from the work and nomogram(s) of Eric Donnenfeld, M.D. and Skip Nichamin, MD, and is printed with their permission. Any medical opinions and/or views expressed in the Calculator are those of Dr. Donnenfeld and Dr. Nichamin and are not necessarily those of J&J Vision and, as such, J&J Vision does not warranty the accuracy or completeness of any such opinions or views.

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LRI Calculator

LRI Calculator
LRI Clinical Information

Surgeon and Patient Information

Eye Selection Scale
Surgeons's View

Keratometry

Nomogram Selection
D°
DFlat MeridianAuto Entry
6.00D
(500 - 1200)microns
Phaco Incision
(0.00 - 1.00)D
(0 - 360)°

Your phaco incision location is within 10° of the Steep Meridian. Try making your phaco incision on the Steep Meridian. Please change the location to match the Steep Meridian and select "Calculate Results". If you want to proceed with the values above, please press the button below.

Thinnest Corneal Depth must be within 500 and 1200 microns.

Steep K must be greater than the Flat K and the astigmatism, including the effect of any surgically induced astigmatism, needs to be at least 0.75 D to recommend an LRI incision (Napa Nomogram).

Steep K must be greater than the Flat K and the astigmatism, including the effect of any surgically induced astigmatism, needs to be at least 0.5 D to recommend an LRI incision (Donnenfeld Nomogram).

Please review any messages and edit any marked fields, then select "Calculate Results" again.

The Donnenfeld nomogram is rated effective up to 3 diopters of astigmatism.
To fully correct all astigmatism, you may need an additional procedure.

Your phaco incision may over-correct the entered amount of astigmatism. Attempt to reduce your induced astigmatism.

Your phaco incision may fully correct the entered amount of astigmatism. The Donnenfeld nomogram does not recommend further LRI (Residual astigmatism after Phaco < 0.5 D).

Your phaco incision should not overlap with the LRI. For this reason, only one LRI is recommended.
You may need an additional procedure to fully correct all astigmatism.

To fully correct all astigmatism, you may need an additional procedure.

The NAPA nomogram is rated effective up to 3 diopters of astigmatism.
To fully correct all astigmatism, you may need an additional procedure.

Your phaco incision may fully correct the entered amount of astigmatism. The NAPA nomogram does not recommend further LRI (Residual astigmatism after Phaco < 0.75 D).

This tool uses vector analysis and assumes the phaco incision will shift the Steep and Flat Meridians as shown in the Results.

Phaco wounds and LRIs should completely overlap when they are close together. Here is a new suggested phaco location.

Results

N
T
T
N
0°
45°
90°
135°
180°
225°
270°
315°
1'
2'
3'
4'
5'
6'
7'
8'
9'
10'
11'
12'
OD
OS
N
T
T
N

55°2.8

55°2.8

110°

99°

222°

55°2.8

Please use NAPA overlap technique Click for tutorial
PhacoNew Steep Meridian
LRINew Flat Meridian
New-Steep K: 45.00 D New-Flat K: 42.00 D (After Phaco)
Astigmatism: 3.00 D Treatment: 3.00 D
LRI-Incision(s): 2 Incision Size: 90°/3.0 c.h.
Residual Astigmatism after LRI: 0.00 D Recommended LRI depth: 603 µ

LRI Clinical Information

About the Nomograms

LRI: A simple way to enhance refractive outcomes during cataract surgery

Cataract surgery presents a one-time opportunity to optimize visual performance, health, and lifestyle. Whether it’s to correct presbyopia or to provide good vision more like that of a healthy younger person, today’s high-technology multifocal and aspheric IOLs now give both surgeons and patients more treatment options. Limbal relaxing incisions (LRIs) give ophthalmic surgeons the opportunity to correct astigmatism at the time of surgery, providing even better visual outcomes to meet patients’ growing expectations.

This guide will describe how to adopt the limbal relaxing incision (LRI) procedure for correcting astigmatism. It will also provide an overview of this free and simple online LRI Calculator software (www.LRIcalculator.com). To use the LRI Calculator software, enter the requested patient information, print out the diagram, and make your incision. Finally, the guide will offer some surgical and administrative pearls for adopting LRIs into your practice.

Astigmatism Overview

Astigmatism is an abnormality of the eye in which vision is blurred by an irregularly shaped cornea. One meridian of the cornea is steeper than the other, causing the cornea to distort images.

There are four different types of astigmatism based on which meridian is steepest:

Treating astigmatism at the cornea is the most logical approach. During cataract surgery, it is possible to correct some or all of this defect through a simple incision— an LRI.

LRI Overview

LRIs “relax” the steep meridian of astigmatism and allow the eye to heal into a more spherical shape. The LRI is made in the limbus, near where the clear cornea and sclera meet. The cornea is relatively thick here, so risk of perforation is lower. LRIs are very forgiving, which is why most nomograms (systems of rules) are simple. Any residual astigmatism may be treated post-operatively through an additional LRI.

Advantages of LRIs include:
• Less tendency to cause meridian shift
• Less irregular astigmatism
• Easier and more forgiving than AK
• 1:1 coupling ratio

The goal of today’s cataract surgeon is to target precise refractive outcomes within 0.5 diopters (D) of sphere and cylinder. In many patients, this goal can be achieved by performing LRIs to reduce astigmatism during the cataract procedure. During cataract surgery, you should consider treating astigmatism through LRIs. You have performed the necessary diagnostics and the patient is already in the mindset of receiving incisions in his or her eye. In most cases, LRIs can reduce a patient’s astigmatism to less than 0.5 D.

Astigmatism in Cataract Patients

The incidence of astigmatism among cataract patients is subject to debate, but one study of 6 thousand cataract patients found that the percentage of patients with at least one diopter of astigmatism was 37.7 percent. This suggests that each year about 1,215,000 US cataract surgical patients have at least mild astigmatism. Currently, only about half of surgeons treat their astigmatic patients surgically. The other half are treated postoperatively with glasses or contact lenses.

In our Market Scope 2020 IOL Market Report Mid-Year Update, cataract surgeons were asked how they treat patients with significant levels of astigmatism. Forty-nine percent of surgeons reported making no attempt to surgically correct astigmatism. When surgery was used, the most common surgical technique reported was the implantation of toric IOLs, which was performed by 33.0 percent of the surgeons. Limbal relaxing incision (LRI), corneal relaxing incisions (CRI), astigmatic keratotomy (AK) and Femtosecond arcuate incisions were collectively employed by 14.2 percent of responding surgeons. LASIK and PRK were used in 1.8 percent of patients. 1

Incidence of astigmatism in cataract patients:

• > 1.0 D = 37.7%
• > 1.5 D = 17.9%
• > 2.0 D = 8.7%

1. Market Scope 2020 IOL Market Report Mid-Year Update for Johnson & Johnson Vision pg 161-163.

Planning for successful LRIs

To plan for an LRI, the best place to start is with diagnostic data. Use data from a keratometer to correctly identify the meridian and amount of astigmatism. Compare this information to the patient’s refracted cylinder. Look for general agreement, but use the keratometer readings because they are not affected by lenticular astigmatism which may contribute to the refractive cylinder but will be removed by the cataract surgery. Perform topography, which should confirm the keratometry cylinder, and pachymetry as you normally would to be sure you are dealing with a healthy cornea. At this point, if you have any doubts, DO NOT PERFORM THE LRI.

Preoperative planning steps
1. Compare keratometer readings and refraction cylinder
2. Confirm keratometric cylinder with topographic cylinder
3. If topography or pachymetry are abnormal, or if you have any doubts, DO NOT PERFORM LRI
4. Go to www.LRIcalculator.com, enter your patient data, and print the LRI report
5. Post the diagram in the OR as a guide

Proven DONO and NAPA Nomograms

The DONO Nomogram (refers to the Donnenfeld Nomogram) and the NAPA Nomogram (refers to the Nichamin Age and Pachymetry Adjusted nomogram) are two widely accepted systems for calculating LRIs. The LRI Calculator software uses either nomogram, according to your preference, for its calculations. The Online Calculator also takes into account the vector from a phaco incision if the LRI is being done at the time of cataract surgery. However, if you would like to make your own LRI calculations, the following charts describe both nomograms. Over time, you should personalize one of these nomograms to your own surgical technique and outcomes.

DONO Nomogram

• Use 5 degrees more for against-the-rule astigmatism
• Use 5 degrees more for younger patients (< 50)
• Use 5 degrees less for older patients (71-80)
• Use 10 degrees less for the oldest patients (> 80)
• Personalize the Donnenfeld Nomogram to your instruments and surgical outcomes

NAPA Nomogram

"With The Rule" (Steep Meridian 31°-149°)

"Blade depth setting is at 90% of the thinnest pachymetry"

"Against The Rule" (Steep Meridian 0-30°/150-180°)

"Blade depth setting is at 90% of the thinnest pachymetry"

LRI Tools and Procedures

The LRI procedure requires use of a diamond blade (preset 600 micron-depth for DONO nomogram and adjustable depth for NAPA nomogram) and incision marker. There is an LRI toolkit package available. The reusable kit contains a pre-set 0.6 mm diamond knife and marker from Accutome. While the patient is sitting up, use the incision marker to mark the meridian of astigmatism, location of the incision(s), and length of the incision(s).

If you are performing cataract surgery, the LRI calculator will take the location of your phaco incision and the amount of induced astigmatism associated with your incision into account when calculating where to make the LRI. In some cases you may only need to make your phaco incision to reduce astigmatism. Perform the LRI before creating your phaco incision. Place a small amount of viscoelastic on the area to lubricate the incision.

Hold the diamond knife like a dart, perpendicular to the cornea, NOT perpendicular to the ground. When you make your limbal relaxing incisions, keep the LRI 0.5 mm inside the limbus in clear cornea. For control, make the incision while pulling the knife slowly toward yourself. Do not make the LRI at the same location where you will make a phaco incision. The LRI procedure can be completed in a few seconds.

LRI Tools and Procedures

In addition to performing LRIs in the OR, they can easily be done in the office.

• Limbal relaxing incisions are easy to perform at the slit lamp
- Anesthetize with lidocaine gel
- Can be repeated one month later
• Use a phoropter to locate incisions and center incisions on the steep meridian (+cylinder)

LRI Procedure at a Glance

1. Tool checklist:
• Incision marker
• Diamond Blade
• Preset 600 micron-depth for DONO nomogram, adjustable depth for NAPA nomogram

2. Making the marks:
• With patient sitting up, mark the:
- Meridian
- Incision location
- Incision length

3. Making the incision:
• Make the incision BEFORE phaco
• Place viscoelastic on the area to lubricate the incision
• Make LRI 0.5 mm inside the limbus in clear cornea
• Hold the diamond knife like a dart
• Cut perpendicular to the cornea (NOT perpendicular to the ground)
• Pull toward yourself for control
• Do not make the incision at the same location where you will make a phaco incision

After the Procedure

With an LRI, there is usually little if any postoperative discomfort. The procedure is safe and is not associated with glare or starburst as often occurs with true corneal incisions (RK and AK). Furthermore, the cornea is usually stable within a week. Use the same antibiotic and anti-inflammatory agent you use with your standard cataract procedure. To reduce postoperative discomfort, use a topical NSAID. For patients with significant remaining astigmatism, it may be necessary to re-treat with LRI.

“When I have an under-correction, I’ll wait approximately one month before augmenting the LRI by lengthening it or deepening it to achieve the desired correction.” – Eric D. Donnenfeld, MD, FACS

Post-OP Overview

• Cornea is usually stable in a week
• Low risk of glare or starburst
• Use the same antibiotic and steroid as with standard cataract procedures
• Use NSAID to reduce postoperative discomfort

Possible Complications

As with any surgical procedure, there are potential complications associated with LRIs, but most are either temporary or correctable.

They may include:
• Under or over correction
• Infection
• Perforation of the cornea
• Decreased corneal sensation
• Induced irregular astigmatism
• Discomfort

Conclusion

To optimize visual results for high-technology IOL patients, surgeons must be committed to reducing astigmatism to within 0.5 D post-operatively. Tracking of results will allow you to fine-tune your technique to achieve your best personal results. Adopting LRIs into your practice can be a valuable exercise. For more information about upcoming LRI training courses or symposiums, contact your sales representative.

Proven DONO Nomogram

The DONO Nomogram (refers to the Donnenfeld Nomogram) is a very simple system for calculating LRIs. The LRI Calculator software uses the Donnenfeld Nomogram for its calculations. The Online Calculator also takes into account the vector from a phaco incision if the LRI is being done at the time of cataract surgery. However, if you would like to make your own LRI calculations, the following chart describes the Donnenfeld Nomogram. Over time, you should personalize this nomogram to your own surgical technique and outcomes.

• Use 5 degrees more for against-the-rule astigmatism
• Use 5 degrees more for younger patients (< 50)
• Use 5 degrees less for older patients (71-80)
• Use 10 degrees less for the oldest patients (> 80)
• Personalize the Donnenfeld Nomogram to your own instruments and surgical outcomes

“The Donnenfeld Nomogram is really a very simple nomogram for developing your skills for performing LRIs. This is an effective procedure and it is not difficult to decide exactly how large to make the incisions or where to place them.” Eric D. Donnenfeld, MD, FACS

Assumptions: DONO Nomogram

Maximum Correction and LRI Length
- The DONO Nomogram is rated effective between 0.5 and 3 diopters of astigmatism. For greater amounts, you may need an additional procedure.
- The maximum suggested length for an LRI is 90 degrees (3 clock hours). Each 90 degree LRI provides approximately 1.5 Diopters of correction.

LRI and the Phaco Incision
- The phaco incision and LRI should not overlap. This constraint limits the maximum amount of correction if there is overlap between the phaco incision and the LRI.
- Where possible, a 10 degree buffer should be kept between the phaco incision and the nearest LRI.

Rounding
- The LRI lengths in this nomogram have been rounded to the nearest 0.1 D of correction and the nearest 5 degrees of length.

Surgically Induced Cylinder
- For surgically induced cylinder of 0 – 0.5 D, the LRI Calculator software assumes the phaco incision is 30 degrees. For surgically induced cylinder of 0.5 – 1.0 D, the LRI Calculator software assumes the phaco incision is slightly larger at 40 degrees.
- The paracentesis (irrigation port) is astigmatically neutral but should not overlap with the LRI.

Proven NAPA Nomogram

The NAPA Nomogram (refers to the Nichamin Age and Pachymetry Adjusted nomogram) is a widely accepted system for calculating LRIs. The LRI Calculator software uses either the DONO or NAPA nomogram, according to your preference, for its calculations. The Online Calculator also takes into account the vector from a phaco incision if the LRI is being done at the time of cataract surgery. However, if you would like to make your own LRI calculations, the following charts describe the nomogram. Over time, you should personalize the nomograms to your own surgical technique and outcomes.

"With The Rule" (Steep Meridian 31°-149°)

"Blade depth setting is at 90% of the thinnest pachymetry"‘
"Against The Rule" (Steep Meridian 0-30°/150-180°)

"Blade depth setting is at 90% of the thinnest pachymetry" “The NAPA Nomogram is proven to be effective between 0.75 and 3 Diopters of astigmatism.” – Louis D "Skip" Nichamin, MD

Assumptions: NAPA Nomogram

Maximum Correction and LRI Length
- The NAPA Nomogram is rated effective between 0.75 and 3 diopters of astigmatism. For greater amounts, you may need an additional procedure. For lesser amounts, you may want to use the DONO Nomogram.
- The maximum suggested length for an LRI is 90 degrees (3 clock hours). Each 90 degree LRI provides approximately 1.5 Diopters of correction.

LRI and the Phaco Incision
- The NAPA nomogram is unique in that the phaco incision and LRI may overlap. This requires using the NAPA overlap incision technique. Using this technique, a portion of the LRI is made first and is completed at the required length and location of the phaco incision. The phaco incision is then performed through this wound. The LRI arc is then extended to the appropriate length as determined by the nomogram. See an illustrated example by clicking here.
- Where possible, a 10 degree buffer should be kept between the phaco incision and the nearest LRI. The LRI Calculator software may suggest slight adjustments to your phaco incision location in order to maintain this buffer.

Rounding
- The LRI lengths in this nomogram have been rounded to the nearest 0.1 D of correction and the nearest 5 degrees of length.

Surgically Induced Cylinder
- For surgically induced cylinder of 0 – 0.5 D, the LRI Calculator software assumes the phaco incision is 30 degrees. For surgically induced cylinder of 0.5
– 1.0 D, the LRI Calculator assumes the phaco incision is slightly larger at 40 degrees.
- The paracentesis (irrigation port) is astigmatically neutral but should not overlap with the LRI.

NAPA Overlap Technique Tutorial (Overlap of phaco and LRI incision)

Occasionally when using the NAPA nomogram you will have a situation where the LRI incision and the phaco incision overlap. This will typically occur in cases of high against-the-rule astigmatism where you are making a temporal phaco incision and the nomogram calls for a temporal LRI incision of greater than 40 degrees. Since this incision will overlap the phaco incision if it is extended to its full arc length at the start of surgery, significant gaping and edema may result secondary to intraoperative manipulation.

In this situation, the temporal incision is made by first creating a two-plane, grooved phaco incision (incision depth based on pachymetry), which is then extended to the full arc length, as determined by the nomogram, at the conclusion of surgery. Note that the keratome used for the phaco tunnel is inserted through the temporal LRI by pressing the bottom surface of the blade downward upon the outer or posterior edge of the LRI, and then advancing the keratome at an iris-parallel plane. This angulation will allow the keratome to enter at mid-stromal depth.

Watch step by step LRI animation (1.20 min.)
Watch Dr. Nichamin's educational talk about LRIs (5 min.)

NAPA Overlap Technique Tutorial (Overlap of phaco and LRI incision) (1.20 min)

Dr. Nichamin's educational talk about LRIs (5 min.)


 
 

Version 4.2.0

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