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Surgical Planning for Astigmatism Management

Increasing Refractive Predictability Through
Enhanced Planning1-3

Today, there are valuable tools for preparing for Astigmatism Management at the time of cataract surgery. Optimizing your surgical plan can increase your opportunity to deliver exceptional outcomes, whether patients present with high corneal astigmatism (≥ 2.0 D) or have low cylinder astigmatism (≥ 0.5–1.5 D).

Alcon toric calculator for Astigmatism Management cataract surgical planning

The ALCON® Online Toric IOL Calculator incorporates the Barrett Toric Algorithm to deliver best-in-class preoperative prediction of residual astigmatism.1,2
Try it now.

Advanced toric calculators can improve your insight into PCA, SIA and ELP for more on-target outcomes

• More precise astigmatic prediction: Theoretically accounting for PCA has the potential to broaden your toric-treatable patient base to include patients as low as 0.5 D*

 

• Improved SIA accuracy: Using centroid vector calculations to incorporate magnitude and direction

 

• More accurate T-power prediction: Accounting for axial length and anterior chamber depth in ELP estimates

*Potential Astigmatism Management patients may have 0.75 D or higher total corneal astigmatism, including those with 0.5 D or higher against-the-rule (ATR) anterior cylinder, as well as patients with 1.25 D or higher with-the-rule (WTR) anterior cylinder.

 

A Breakthrough in Astigmatism Correction Planning

When the Barrett Toric Algorithm is incorporated into a toric calculator, it helps deliver best-in-class preoperative prediction of residual astigmatism.1,2 The ALCON® Online Toric IOL Calculator is the only web-based toric calculator to offer surgeons the added precision of the algorithm, which was inspired by innovative thinking:

Factoring in PCA Can Reveal Additional Toric IOL Candidates

Astigmatism Management means looking at the cornea differently. Evaluating both anterior corneal astigmatism (ACA) and posterior corneal astigmatism (PCA) may prevent overcorrection in WTR eyes and undercorrection in ATR eyes.4

The ALCON® Online Toric IOL Calculator theoretically accounts for PCA, increasing your opportunity to deliver excellent, lasting visual acuity to a larger patient population. If you use it to calculate IOL power for every cataract patient, you could discover toric IOL candidates with ACA as low as†,4:
• 0.5 D ATR
• 1.25 D WTR

AcrySof® IQ Toric IOLs are appropriate for patients with 0.75 D or greater total corneal astigmatism, which includes those with 0.5 D or higher against-the-rule (ATR) anterior cylinder, as well as patients with 1.25 D or higher with-the-rule (WTR) anterior cylinder.

Rethinking SIA Can Help You Hit Your Refractive Target

Accurate preoperative SIA prediction is crucial to hitting refractive outcomes.1 Conventional wisdom says the cornea flattens along the incision axis during cataract surgery, but living, breathing tissue reacts to incisions differently from eye to eye. Even with consistent techniques, corneal flattening during cataract surgery is unpredictable.3

So what can we do to ensure accurate SIA prediction?

Viewing astigmatism as a vector

Traditional mean SIA
calculation relies on
magnitude alone.

 
Traditional mean SIA calculation relies on magnitude alone.
 
Double angle vector diagrams are used to find the centroid SIA value.

Precise mean SIA calculation considers magnitude and direction

Using vector analysis to find the geometric mean, or centroid, yields the highest prediction accuracy of any method.

Double Angle Vector Diagram

  • Patients’ SIA values are plotted by power and axis
  • Axes are doubled to visualize full spectrum of astigmatism
  • Opposing vectors negate one another, producing centroid of all data points
  • Diagram visualizes the net effect of SIA
 

By applying vector analysis to a broad sample of post-op patient astigmatism data, the industry standard value has evolved.

  • Traditional mean SIA: 0.5 D
  • Centroid SIA: 0.1 D**
 

The ALCON® Online Toric IOL Calculator with the Barrett Toric Algorithm is designed to provide the most accurate preoperative prediction of residual astigmatism — in part by using the modern centroid value (0.1 D) for SIA.1,2,5

**Recommended for incisions between 2.2 and 2.4 mm.

Choosing the Right Surgical Approach

In theory, a surgical plan that involves correcting astigmatism with glasses or spherical equivalent can get patients’ vision to plano, but those methods have their shortcomings.

Spherical Equivalent:

SEQ has long been thought of as a solution for astigmatism, but at best it masks the problem.

Which spectacle correction would you prescribe for the patient below?

  Patient Smith:

MR OD: -3.25 D + 1.00 D x 180


MR OS: -2.75 D + 1.00 D x 175

Spectacle prescription options:

A) OD: -2.75 sph & OS: -2.25 sph


B) OD: -3.0 + 0.5 x 180 & OS: -2.5 + 0.5 x 175


C) OD: -3.25 + 1.00 x 180 & OS: -2.75 + 1.00 x 175

Would you prescribe A or B, which do not fully address the patient’s astigmatism?
If you wouldn’t use SEQ with spectacles, why would you use it in cataract surgery?

Spectacles:

Residual cylinder can reduce quality of vision even when glasses manage visual acuity to 20/20.6 If you can address your patients’ astigmatism during surgery, why wouldn’t you?

Toric IOLs:

A proven way to address residual blur that diminishes functional vision.6

The Consequences of Uncorrected Astigmatism

The Alcon astigmatic vision simulator is designed to show you life with unmanaged astigmatism.

Learn about Intraoperative Astigmatism Management

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  1. Abulafia A, Barrett GD, Kleinmann G, et al. Prediction of refractive outcome with toric intraocular lens implants. J Refract Surg. 2015;41(5):936-944.
  2. Abulafia A, Hill WE, Franchina M, Barrett GD. Comparison of methods to predict residual astigmatism after intraocular lens implantation. J Refract Surg. 2015;31(10):699-707.
  3. Mingo-Botín D, Muñoz-Negrete FJ, Kim HRW, Morcillo-Laiz R, Rebolleda G, Oblanca N. Comparison of toric intraocular lenses and peripheral corneal relaxing incisions to treat astigmatism during cataract surgery. J Refract Surg. 2010;36(10):1700-1708.
  4. Koch DD, Ali SF, Weikert MP, Shirayama M, Jenkins R, Wang L. Contribution of posterior corneal astigmatism to total corneal astigmatism. J Cataract Refract Surg. 2012;38(12):2080-2087.
  5. Alpins N, Barrett GD, Hansen MS, Berdahl JP, Hardten DR, Holladay JT. Innovative toric IOL calculators and how to use them: Barrett Toric Calculator. Cataract Refract Surg Today Europe. May 2015 supplement.
  6. Watanabe K, Negishi K, Kawai M, Torii H, Kaido M, Tsubota K. Effect of experimentally induced astigmatism on functional, conventional, and low-contrast visual acuity. J Refract Surg. 2013;29(1):19-25.