The HOYA Toric Calculator (HTC) is a resource for the treating physician to aid in proper IOL cylinder power selection for cataract patients with corneal astigmatism. The HTC requires the user to input patient biometric data and planned surgery information that is part of an ophthalmic work up prior to Toric IOL (TIOL) implantation. The HTC will suggest several HOYA TIOLs from which the surgeon may choose to treat a patient’s refractive cylinder resulting from corneal astigmatism. The HTC will also provide suggested intra-operative axial placement of the IOL that is intended to minimize postoperative astigmatism based on the information provided. The recommended lenses and axis of placement are to be informative for the user and are not intended to replace the medical expertise or judgment of the surgeon or operator.

The HTC is openly accessible on the internet for all users. The calculator can be found at and This calculator is compatible for use with internet browsers including Internet Explorer (ver. 9 or newer), Google Chrome (40 or newer), Firefox (ver. 38 or newer) and Safari (ver. 8 or newer).

Upon entering the website with a compatible internet browser, the user will be led to a page that will prompt the user to select a language for use and to select a geographic region or country. The choice of region will restrict the toric IOL models offered to those available in the specified region. User should click the “Submit” button to move forward.

After reading the Terms and Conditions, the user must click the “I Accept” button to indicate acceptance and advance to enter patient information.

After accepting the Terms and Conditions, the data input page is shown.

Using the tab key to advance to the next field, a complete set of data must be entered by the user as prompted by the calculator for the following entries:

The user must enter the following required information:

Surgeon Name  Patient identification

The user may also choose to enter the following optional information:

Clinic Name  Birthdate

Secondary Patient ID  Gender

All information entered will be shown in printed output.

Eye Selection – Upper-left corner of the graphic image of the eye
The user must select Right Eye-OD or Left Eye-OS from a pull down tab.

Keratometry Information

  • Flat K: User must enter the patient’s corneal curvature value on the flat axis as measured by keratometry in either mm radius or diopters. The entered value must be within a range of 6.75 to 9.75 mm or 35.00 to 50.00 diopters.
  • Flat Axis: User must enter the angle of the corneal flat axis as measured by keratometry in the range of 0° to 180°.
  • Steep K: User must enter the patient’s corneal curvature value on the steep axis as measured by keratometry in either mm radius or diopters. The entered value must be within a range of 6.75 to 9.75 mm or 35.00 to 50.00 diopters.
  • Steep Axis: A value that is 90° from the flat axis will automatically be generated. The user may change that value by + or - 5°.
  • Surgically Induced Astigmatism: User must enter a value in a range from 0.00 to 2.00 diopters for the expected change in corneal astigmatism due to the surgical incision.
  • Incision Location: The user must enter the incision location from 0° to 359°.
  • Spherical Equivalent IOL Power: User must select from the pull down tab the appropriate value of the spherical power of the lens.

All numeric entries that are decimal values may be entered using either a dot (.) or a comma (,) to serve as the decimal point. For example, 1.05 may be entered or as 1,05 and will be recognized by the calculator as the same value.

Calculation Result and IOL Selection

After the complete data set is entered, the graphic image of the eye will update to show the entered data values. The calculator will also automatically generate three toric lens options of different cylinder power for the user to consider. Astigmatic correction will be calculated for all toric lens powers and for a non toric lens according to the following properties:

The calculator will display up to three lens options depending on the input information. The toric IOL options will be listed from left to right as under correcting astigmatism to over correcting astigmatism. The lens selection shown as “Option 2” in the center will be the TIOL with cylinder power that will minimize the patient’s astigmatism without over-correcting the cylinder and rotating the astigmatic axis. Option 1, on the left, is the TIOL that is the next available IOL cylinder power lower than Option 2. Option 3 on the right is the TIOL that is the next available IOL cylinder power higher than Option 2; this TIOL might indicate residual astigmatism close to zero but will result in rotation of the axis of astigmatism 90°. These lens offerings are informative for the user and the selection of one of these lenses is solely based on the medical expertise of the surgical team to provide the best correction for their patient.

The HTC will also inform the user of the recommended axis for TIOL placement and will include an image of the eye with the incision location, steep and flat corneal axes, and the axis of placement for the TIOL.

The user must select one of the lenses offered or may re-enter any of the values to recalculate. If Option 3 is selected a warning will appear that says, “Your selection has the potential to rotate the patient’s axis of astigmatism 90°. Do you want to proceed?” The user must select yes to proceed or no to return to the data entry page. A “Clear Fields” button is available in the middle of the page to restart data entry.

* Based on an average pseudophakic human eye

Upon selection of the lens, the screen updates to display the selected IOL.

The user will be prompted to select a lens model for the print out. Using the pull down tab the user can select only HOYA Toric IOL models available in his/her region. The lenses will be listed by model number. Also, the software will offer an option that shows no model number, but lists the toric IOL spherical and cylinder power with the placement axis.

For more product information please contact your local sales representative.
**Some intraocular lens models described in the table may not be approved for sale in your country. Please check with the HOYA distributor in your country for a full list of IOL models available in your country.

The user can select an orientation of the image of the eye for print using the pull down tab on the upper right of the eye image. The orientation of the eye image can be printed from the following three options:

Exam Room View  Surgeon's View - Superior  Surgeon's View - Temporal

The user’s individual computer, network settings, choice of web browser and software settings may affect optimum performance of the toric calculator. These variables may prevent the site from providing results or may result in less than optimum printed output. Please use the guidance below to investigate and correct likely issues.

  1. JavaScript and Cookies must be enabled
    1. JavaScript settings can usually be found in your browser toolbar under Tools/Options/Content section
    2. Cookies settings can usually be found in your browser toolbar under Tools/Options/Privacy
    3. Additional plug-in or programs could be preventing JavaScript or cookies from working properly.
  2. Printer settings
    1. If your printer does not print immediately please allow 4-5 seconds for the printer driver to open
    2. If your printer driver still does not come up:
      1. Look for a browser indicator or yellow bar at the top or bottom of the page that will enable printing, set it to always allow printing from this website.
      2. Active Scripting – If the computer is on a work network the security setting on your computer or network may not allow active scripting and block the printer driver. Please work with your IT department to enable active scripting for this website.
    3. If your printout is not optimized to fill a single page, printer settings can usually be found in your browser toolbar under File/Page Setup.
      1. Scale to fit the page – Enabling Shrink to Fit should optimize a single page print-out. If that doesn’t work, then use the print scale to optimize the print-out.
      2. Header and footer - Displaying web page titles and URLs in the header or footer of the printout may be default settings of your browser. These can be turned on or off to format the printout as desired.
  3. Browser Backward / Forward buttons – Please use the active buttons on the website or the progress bar at the top of the pages where ever possible to navigate through the steps of entering data, going forward or backward to change or update information. The action of the browser’s back button is not controlled by the web site and may be handled differently depending on the browser used.
  4. 30 minute time out – If the user leaves their session at the site for more than 30 minutes the site will not retain data and refreshing the page will redirect the user to the home page.
  5. Contact HOYA – All entries on the Contact HOYA page should be made using Latin (English) characters, as other characters cannot be processed. Other character sets, like Japanese or Arabic, used in the name and email fields will not be recognizable to the HOYA representative receiving the message.

2-7-5 Naka-Ochiai, Shinjuku-ku,
Tokyo 161-8525 Japan
Authorized Representative in the European Community:
HOYA Surgical Optics GmbH
De-Saint-Exupéry-Str. 8
60549 Frankfurt am Main Germany
Year of Manufacture:


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