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Intra-Operative Considerations Tecnis Synergy Toric II 

The following section describes steps that can be taken to help position the selected lens during surgery for optimal results.

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Spherical Equivalent Power

When using intraoperative aberrometry, if the system has not been optimized, do not choose the TECNIS Synergy™ lens from the IOL menu. Choose the ZCB00 TECNIS 1-Piece IOL to determine the spherical equivalent power.

Capsulorhexis

A consistent curvilinear capsulorhexis is critical for centration and accurate effective lens position.

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Lens Centration

For the selected lens to work as well as possible, it needs to be centered in the right place in the eye for the individual patient. Doctors will use Purkinje Images and angle kappa information to aid with appropriate lens placement.3

(Purkinje images are reflections of objects from the structure of the eye. The Kappa angle is defined as the angle difference between the visual axis and pupillary axis.*)

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Example of visible first Purkinje image where patient is fixating on a single coaxial microscope light

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Lens Centration if angle kappa < 5°

While patient is fixating on the single coaxial microscope light, center the first diffractive ring on the first Purkinje image. 

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Lens Centration if angle kappa > 5°

If angle kappa is larger (> 0.5 mm), center the first diffractive ring in between the pupil center and the first Purkinje image (P 1). This will effectively center the TECNIS Synergy™ lens at the midpoint of the angle kappa.

OVD Removal & Capsule Capture of IOL

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After implantation of the TECNIS Synergy™ IOL, remove all OVD including behind the IOL, then push posteriorly to aid in capsule capture

Purkinje Images

Purkinje images are reflections of objects from the structure of the eye. They are also known as Purkinje reflexes and as Purkinje–Sanson images. 

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At least four Purkinje images are usually visible:

  • The first Purkinje image (P1) is the reflection from the outer surface of the cornea. 

  • The second Purkinje image (P2) is the reflection from the inner surface of the cornea.

  • The third Purkinje image (P3) is the reflection from the outer (anterior) surface of the lens.

  • The fourth Purkinje image (P4) is the reflection from the inner (posterior) surface of the lens. Unlike the others, P4 is an inverted image.

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The third and fourth Purkinje images can be visible from within the eye itself. Light reflected away from the surfaces of the lens can in turn reflect back into the eye from the rear surface of the cornea. These images are, therefore, entoptic phenomena.

The first and fourth Purkinje images are used by some eye trackers, devices to measure the position of an eye. The cornea reflection (P1 image) used in this measurement is generally known as glint.

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Angle Kappa

Kappa angle is defined as the angle difference between the visual axis and pupillary axis. The Visual axis connects the point of fixation with the fovea. The Pupillary axis is the line through the centre of the pupil perpendicular to the cornea

  • Kappa angle varies:

    • From 3.5 to 6° in emmetropic eyes

    • From 6.0 to 9.0° in hyperopic eyes

    • From 2° adn even negative in myopic eyes

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Kappa
Possible complications with diffractive multifocal IOLs
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Temporal decentration of a diffractive multifocal al IOL was associated with the greatest risk of photic phenomena.

The assumed cause of pronounced photic phenomena after implantation of diffractive-design MIOLs in patients with a higher angle kappa is that the fovea centric ray would pass closer to the edge of the rings and not through the central area of the MIOL if angle kappa is larger (> 0.5 mm)

Lower ELP values (more anterior IOL placement) in combination with high kappa angle may increase the risk for pronounced photic phenomena after multifocal IOL implantation.

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ELP (Effective Lens Position) and preop anterior chamber depth (ACD) are interdependent2 therefore shallow anterior chamber depth in connection with a higher angle kappa could be an important risk factor for pronounced photic phenomena after multifocal IOL implantation

Intra-Operative Considerations summary: 


a. When using intraoperative aberrometry, if the system has not been optimized, do not choose the TECNIS Synergy™ lens from the IOL menu. Choose the ZCB00 to determine the spherical equivalent power.

 

b. A consistent curvilinear capsulorhexis is critical for centration and accurate effective lens position.

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c. After implantation of the TECNIS Synergy™IOL, remove all OVD including behind the IOL, then push posteriorly to aid in capsule capture.

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d. While patient is fixating on the single coaxial microscope light, center the first diffractive ring on the first Purkinje image. If angle kappa is larger (> 0.5 mm), center the first diffractive ring in between the pupil center and the first Purkinje image.This will effectively center the TECNIS Synergy™ lens at the midpoint of the angle kappa.

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Refractive Targeting
a. To optimize distance through near vision, select the IOL power that gives residual refraction closest to plano
b. When equidistant from plano, choose the lens that will target slight hyperopia.
c. Targeting myopia is neither recommended nor necessary.

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Use the most optimized IOL constant
a. If you have a personalized A-Constant for TECNIS® Monofocal (ZCB00), use it for TECNIS Synergy™ IOL Power Calculation.
b. In the absence of a personalized A-constant for TECNIS® Monofocal (ZCB00), use the labeled TECNIS Synergy™ A-constant (optical 119.3).
c. Personalized A-Constants for TECNIS® Multifocal IOL must not be used for TECNIS Synergy™ IOL power calculation.

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Ensure the correct patient values are calculated (preop- measurements)
Use an Optical Biometer and ensure that measurements are reliable.

 

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