This Surgically Induced Astigmatism Calculator (SIA Calculator) has been
designed to calculate, by means of vector analysis, the amount of surgically
induced astigmatism created during the cataract surgical procedure. Please
feel free to download this calculator, place it on your computer and then
add cases sequentially.
Windows: Microsoft Office 200, or later is required. In order to
run the SIA Calculator application the Macros must be enabled. (Choose Tools> Macro > Security
and choose Medium for a signed macro.)
Macintosh: Office 2001 for
Mac or later is required and Macros must be enabled. Detailed instructions
can be found under the instructions tab of the SIA Calculator download.
When entering patient data into the SIA Calculator, it is always best to
use the same instrument for pre and post-op keratometry measurements. Manual
keratometry or autokeratometry is preferred over simulated Ks. Also, please
take care not to flip the pre and post-op meridians. Pre and post-op data
should be entered in the corresponding steep or flat meridian. After cataract
surgery, the axis in each of the two principal meridians should only shift
between 5 degrees and 20 degrees; and, unless a very large incision is used,
the power change should be less than 1.00 D.
Keratometry measurements are typically between 35.00 and 50.00 diopters.
Measurements outside this range are unusual and should be re-verified. Axis
measurements must be an integer between zero and 180 degrees. The axis of
the steepest and flattest meridian should differ by 90 degrees +/- 5 degrees.
Values outside this range may indicate irregular astigmatism and should be
re-verified. The incision location must be an integer between zero and 360
degrees. Look at the picture under the SIAReport tab for a graphic representation
of the convention for incision location.
This individual patient information will be automatically summarized in
the SIA Calculator by incision type, size, and location by using the built-in "Create
Report" function.
After you have enough cases to generate a report, the magnitude of surgically
induced astigmatism will be visible under the SIAReport tab. This information
can then be entered into the "Surgically Induced Cylinder (SIC)" field
of the Alcon AcrySof Toric
IOL Calculator (acrysoftoriccalculator.com/Country.aspx).
A
tutorial for its use can be viewed by clicking on the "Tutorial"
menu item at the bottom of the calculator page.
PLEASE
NOTE
Dr. Hill requests your assistance in putting together a database of
information collected from surgeons around the world to be included in
an analysis of surgically induced astigmatism. These data will be analyzed
in total, so that we may further understand surgically induced astigmatism.
If you would like your data to be included in this important analysis,
please upload your SIA Calculator information to the database. Instructions
for sending data can be found under section VII (Send Data). Please note
that no patient names will be sent to the database.
This Excel spreadsheet can be used to submit data for optimizing the a0,
a1 and a2 constants for the Haigis formula. The corneal power should be entered
in diopters and not mm.
IMPORTANT:
Because this exercise requires Dr. Hill a significant time to complete,
requests for this service must come DIRECTLY FROM THE SURGEON whose data this represents
and NOT from support staff. Requests from support staff WILL
BE RETURNED UNANSWERED.
Address your subject line to
read: "Haigis optimization." Along with the completed
Haigis-300.xls spreadsheet, the text of the e-mail should include the manufacturer
and model of the IOL, such as Alcon SN60WF, the biometry method employed,
such as the IOLMaster and the name of the requesting surgeon. If less than
200 valid cases are submitted, only the a0 Haigis constant will be optimized
with the Haigis a1 and the a2 constants remaining at default values. It is
best to submit approximately 225 cases so that more than 200 cases will remain
after the exclusion of any outliers.
This download is a set of detailed instructions on how to complete
and submit the Excel spreadsheet that will be used to derive your set
of surgeon and IOL specific a0, a1 and a2 Haigis constants.
The above .pdf file contains the checklist that our staff uses when measuring
the axial length, central corneal power, ACD, and horizontal corneal diameter
using the IOLMaster. The .pdf file contains three identical checklists. We
suggest separating each copy and having them laminated individually to allow
various staff members easy access to their own copy.
East Valley Ophthalmology provides this on-line
information for educational and communication purposes only and
it should not be construed as personal medical advice. Information
published on this website is not intended to replace,
supplant, or augment a consultation with an eye care professional
regarding the viewer/user's own medical care. East Valley Ophthalmology's
disclaims any and all liability for injury or other damages that
could result from use of the information obtained from this site. Please read our full Disclaimer.
IOLMaster Manual V.5.4 (pdf)
PLEASE
NOTE
