Axial Length

The distance in mm from the corneal epithelium to the "fovea." Ultrasound biometry measures the distance to the internal limiting membrane. The Optical biometry measures to the retinal pigment epithelium. The system will accept axial length values between and including 12.00 and 40.00mm.

Method

The system offers five options, related to the biometry measurement and IOL constant selection:

• Optical or Immersion
• Ultrasound/Contact
• Personalized A-Constant
• Personalized Surgeon Factor
• Personalized Anterior Chamber Depth

Optical biometry (eg: IOLMaster, Lenstar), immersion A-scan and contact ultrasound A-scan have fixed A-constants. The last three options are for those surgeons who have developed their personalized IOL constants based on their own patients implanted with the TECNIS® IOL. Personalized constants for the corresponding non-Toric model (i.e. Model ZCB00) are valid starting points for Toric model calculations. For surgeons without personalized constants, the IOL constant for the selected biometry procedure will be used in the cylinder power calculation.

Note that the formula used for cylinder power calculation is the Holladay-1.

A-Constant

IOL A-Constant is a numerical value used in IOL power calculations. The system offers three options:

• TECNIS® Toric lens A-Constant per Optical or Immersion: 119.30 and 119.10
• TECNIS® Toric lens A-constant per Ultrasound/Contact: 118.80 and 118.60
• TECNIS® Toric lens Personalized A-Constant range: 110.00 and 125.00

Surgeon Factor

Personalized Surgeon Factor range: -3.31 and 5.19

ACD

Personalized Anterior Chamber Depth (ACD) constant range: 0.30 and 9.05

SE IOL Power

The Spherical Equivalent IOL Power calculated by surgeon’s choice method for the particular eye for which the cylinder calculation is being performed: The system will accept SE IOL power value entries in the approved range for the selected lens in 0.5D increments.

K-index

The equivalent refractive index of the keratometer. A numerical value used to convert radius of curvature to keratometric power according to the keratometer used to get the inputs for the keratometry section. The system will offer four values as displayed through a drop-down choice list: 1.3375, 1.336, 1.332, and 1.3315.

Refractive Cylinder Convention

Calculated residual astigmatism related to each suggested lens model can be written in either of two equivalent forms: Plus Cylinder or Minus Cylinder. It can be changed back and forth once the calculation has been performed.

e.g., +0.01D x 90º (Plus Convention) = -0.01D x 0º (Minus Convention)

Plus to Minus:

Cylinder: sign + to –

Axis: change ± 90º

IOL Details: IOL Model

Cylinder power suggested for this particular patient based on performed calculations. Different lens models (two or three, depending on the case and available models) are shown.

IOL Details: Orientation

Calculated IOL orientation for each lens model shown. This output is also displayed in the pictorial scheme.

Residual Astigmatism: Cylinder

Calculated residual cylinder for each IOL model displayed, according to the refractive cylinder convention (Plus or Minus) chosen at the Calculation Preferences.

e.g., +0.01D x 90º

Residual Astigmatism: Axis

Calculated residual cylinder axis for each IOL Model shown.

e.g., +0.01D x 90º

Note: Once the IOL model is selected by clicking on it, a pop-up message appears if the residual cylinder axis is flipped to indicate an overcorrection of the patient’s astigmatism.

Surgically Induced Astigmatism (SIA)

Expected induced astigmatism from corneal incision, to be entered by the surgeon. The system will accept surgically induced astigmatism values between and including 0.00 and 2.00D.

@ Meridian

Corneal incision location. The system will accept incision location values between and including 0 and 360°.

Flat and Steep Keratometry Power

Flat K (K1) is the measurement of the flattest corneal power in diopters (D) or flattest corneal radius in millimeters (mm). Steep K (K2) is the measurement of the steepest corneal power in diopters (D) or steepest corneal radius in millimeters (mm).

• When keratometry units are set to D, steep K2 must be greater than or equal to Flat K1. The system will accept keratometry power values between and including 20.00 and 80.00D.
• When keratometry units are set to mm, steep K2 must be less than or equal to the Flat K1. The system will accept keratometry radius values between and including 4.22 and 16.88mm.

Flat K1 @ Meridian

The system will accept keratometry Flat K1 @ meridian values between and including 0 and 180°.

The system will auto calculate the keratometry Steep K2 @ meridian value.

• Flat @ meridian ± 90° = Steep @ meridian

Preoperative Corneal Astigmatism

The calculated value representing the difference between the keratometry power Steep K2 and Flat K1 (i.e., Steep K2 – Flat K1), without including the surgically induced astigmatism or posterior corneal astigmatism in the calculation.

• The Preoperative Corneal Astigmatism value will only be displayed as a Diopter unit.

Include Posterior Corneal Astigmatism (where available)

This checkbox is for optional inclusion of an algorithm to account for posterior corneal astigmatism. The option to include the predetermined value of posterior corneal astigmatism is based on an algorithm that combines published literature (Koch DD et al. Contribution of posterior corneal astigmatism to total corneal astigmatism. J Cataract Refract Surg. 2012 Dec;38(12):2080-7) with a retrospective analysis of existing clinical data.

Surgeon Name

This field is not required; this information is used to help identify the surgeon for whom the calculation is being done.

Date

This field is used to indicate the calculation date. To change the date, select from the drop down menu.

Patient Information

This field is a free form text field that you can use to identify the patient for whom this calculation is being performed.

Patient age

This field is used to capture the age of the patient for whom the calculation is being performed.

Eye Selection

This field is used to select the left or right eye that you wish to perform the calculation for.

K Notation

These radio buttons enable the selection of the K notation preference to be used for the current calculation. Calculations can be performed in Diopter or mm units.

Notes

This field is a free form text pop up field that allows the user to input any additional information as needed. This notes field will appear in the printed results page.

The cylinder power is below the range for Tecnis Toric IOLs, please consider a non-toric Tecnis IOL.

The clinical study for the TECNIS® Toric 1-piece IOL did not show evidence of effectiveness for the treatment of preoperative corneal astigmatism of less than one diopter.

Please confirm that you wish to clear all entries that you have made on this screen. (e.g., OD (Right) & OS (Left))

Patient information has changed. Do you want to clear all entries? (e.g., OD (Right) & OS (Left))

Lens has changed. Do you want to clear all entries? (e.g., OD (Right) & OS (Left))