BESST II IOL POWER CALCULATOR                                    



How do I find out my computer’s SITE CODE?

  1. The Site Code is a unique code that identifies each personal computer. To find out your Site Code you simply have to launch BESSt IOL Power Calculator (Start Menu / All Programs / BESSt).

  2. It is not possible to activate the program if you send us an invalid Site Code. So watch out for spelling mistakes as they will delay the software activation.

  3. You can not choose the Site Code your self! The Site Code has nothing to do with your Address or Zip Code. It is instead a unique number to distinguish one computer from another one.  

  4. Pay attention when taking note of the Site Code: it should contain only CAPITAL LETTERS and NUMBERS. Take care not to mix zeros, “0”, with the letter “O”. It’s a very common mistake!

  5. To avoid making mistakes we suggest the following procedure to enter the Site Code correctly in the Application Form:

  6. Double-click on the Site Code (make sure it is all selected)

  7. Copy it (Ctrl + C)

  8. Paste it into the Application Form (Ctrl + V)

Still waiting to receive a Site Key?

  1. If you’ve been waiting for over 5 working days to receive a reply from us, first check in your spam mail folder if you can find the message. If you cannot find it, first make sure you can receive emails from on your email account (you may need to add this email address to your Contacts and make sure you don’t have any other spam filters enabled) and then apply again via the Application Form.

On how many computers can I activate the Full License?

  1. On a single one. If you need extra Licenses for other computers you need to request an Off-line License in the Apply for License Section.

What if I change computer after I have purchased the Full License?

  1. No problem. You will just need to inactivate the old License first (after backing up the database) and then we will issue you a new activation code for the new computer. In order to inactivate the License you will have to launch the program and go to Help/Permanently remove license. This will generate a code that will prove that the License has been permanently removed from your computer. You will have to send this code to us by email in order to receive the code for the new computer. ATTENTION: once this process is done, BESSt will never be able to run again on that computer.

Is there a version for Mac?

  1. Soon!

Is there a version for iPhone/iPod Touch?

  1. Yes! Visit or Apple Store for more info.


Can I use radii of curvature from other devices like the Orbscan?

  1. Corneal curvature measurements taken with other instruments are not supported and may lead to serious refractive errors as BESSt formula originates from very fine tuning and regression analysis based on measurements taken only with the Oculus Pentacam.

Axial Length (AL) measurements: US or IOL Master?

  1. Axial Length should ideally be taken with the IOL Master (Carl Zeiss Meditec™, Germany) for grater accuracy.

Standard or Customized A-Constants?

  1. For better accuracy we advise using optimised Constants as opposed to the labelled ones.


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