Systematic approach to toric IOL power calculation HNascrs16.expoplanner.com/handouts_ascrs/001636... · 4/9/2016 3 81 eyes LEI IOLMaster2 68 eyes Ein-Tal Lenstar1 Errors in Predicted

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Corneal astigmatism measurements

Methods of calculation

Corneal surgically induced astigmatism (SIA)

Toric IOL misalignment

Sources of

Unexpected residual astigmatism!

& 180

Single-angle vs. double-angle plots for astigmatism data

ATR ATR

WTR

WTR ATR

Toric IOL cylinder power at the corneal plane is

calculated by using a fixed ratio:

Alcon

Oculentis

PhysIOL

Commercial Toric IOL calculators

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Toric IOL cylinder power at the corneal plane is

calculated by using the estimated ELP.

AMO

Medicontur

Rayner

Zeiss

Holladay, ASSORT, Barrett

Commercial Toric IOL calculators

Toric IOL cylinder power at the corneal plane is

calculated by using the estimated ELP.

AMO

Medicontur

Rayner

Zeiss

Holladay, ASSORT, Barrett

Commercial Toric IOL calculators

0.7 D difference

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3

81 eyes

LEI

IOLMaster2

68 eyes

Ein-Tal

Lenstar1

Errors in Predicted Residual Astigmatism

1. Abulafia et al, J Cataract Refract Surg 2015; 41:936-9442. Abulafia et al, J Refract Surg 2015; accepted for publication

Commercial Toric IOL calculators

Q: Does the ELP make a difference?

A: Yes, but…mostly for extreme cases

81 eyes

LEI

IOLMaster2

68 eyes

Ein-Tal

Lenstar1

Errors in Predicted Residual Astigmatism

1. Abulafia et al, J Cataract Refract Surg 2015; 41:936-9442. Abulafia et al, J Refract Surg 2015; accepted for publication

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Standard keratometric and topography machines

tend to yield inaccurate results in assessing the net

corneal astigmatic power

Posterior Corneal Astigmatism

Posterior Corneal Astigmatism

Koch et al, J Cataract Refract Surg 2012;38:2080-2087

715 eyes of 434 patients

Posterior Corneal Astigmatism

Koch et al, J Cataract Refract Surg 2012;38:2080-2087

WTR

ATR

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Most posterior corneas are steep vertically

The posterior cornea acts like a negative lens

It creates a net plus power along the horizontalmeridian

ATR astigmatism

What is the effect of the posterior corneal astigmatism?

Koch et al, J Cataract Refract Surg 2012;38:2080-2087

81 eyes

LEI

IOLMaster2

68 eyes

Ein-Tal

Lenstar1

Errors in Predicted Residual Astigmatism

1. Abulafia et al, J Cataract Refract Surg 2015; 41:936-9442. Abulafia et al, J Refract Surg 2015; accepted for publication

Intraoperative aberrometry

Standard toric IOL calculators + Nomogram (Baylor)

Barrett Toric IOL calculator

Standard toric IOL calculators

+ Direct measurements of the PCA (Scheimpflug, OCT,

Cassini)

Standard toric IOL calculators + AK (Abulafia-Koch) formula

Solutions:

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Baylor Nomogram:

Koch et al, J Cataract Refract Surg 2013;39:1803-1809

The Barrett Toric Calculator

SEq Universal II formula

ELP IOL cylinder power correction at the corneal plane

Mathematical model Net corneal astigmatism !

P< .001 (J0)

Each ring = 0.50 D

99 eyes

LEI

IOLMaster & Holladay

Pentacam & Holladay

IOLM-Pentacam & Holladay

IOLMaster & Barrett

Errors in Predicted Residual Astigmatism

Abulafia et al, J Refract Surg 2015; accepted for publication

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The Abulafia-Koch (AK) formula

Abulafia et al, Barcelona, ESCRS 2015

J0: Regression of estimated net corneal astigmatism by measured corneal astigmatism (R²=0.986)

J45: Regression of estimated net corneal astigmatism by measured corneal astigmatism (R²=0.963)

AK Formula – ATR astigmatism

The AK formula calculates the estimated net corneal astigmatism, by using anterior corneal based measurements!

AK Formula – WTR astigmatism

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AK Formula – oblique astigmatism

Centroid Error in Predicted Residual Astigmatism

WTR ATR

Each ring = 0.50 D

(P< .0001 [J0]; P= .986 [J45])

Abulafia et al, accepted as an abstract, Barcelona, ESCRS 2015

Centroid Error in Predicted Residual Astigmatism

WTR ATR

Each ring = 0.50 D

(P= .986 [J0]; P= .990 [J45])

Abulafia et al, accepted as an abstract, Barcelona, ESCRS 2015

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61 years old female

Ref: -7.75, -0.75x161°

AL = 27.21mm, mean K = 43.02 D, ACD = 3.19 mm

Example: WTR Astigmatism

Primary instrument

Axial power map

Steep meridian: 87°

Supporting instruments

IOLMaster

Steep K: 89°

Lenstar

Steep K: 86°

Primary and secondary supporting instrumentsdetermining the steep meridian

Use primary and secondary supporting instrumentspower difference between meridians

Primary instrument

Lenstar KeratometryPower difference

Pentacam front power map: 2.4 D

Supporting instruments

IOLMaster Keratometry: 2.21 D

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Toric IOL Calculation

+ AK

Toric IOL Calculation

+ AK

Toric IOL Calculation

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Error in predicted residual astigmatism

LE uneventful cataract extraction, SN6AT4, 11.5 D

Post op refraction (cyl): 0.25D x 155° cyl

Alcon: 0.61 D x 167° ; Holladay: 0.68 D x 168°

Holladay (pentacam) TCRP: 0.80 D x 166°

Posterior astigmatism: 0.53 D x 167°

Alcon + AK: 0.14 D x 114°

Holladay + AK: 0.14 D x 133°

Barrett: 0.16 D x 142°

The outcome of toric IOL implantation can be optimized by using ‐

Appropriate methods of calculation

Summary

+ AK + AK