1. What is the optical zone and depth?  

The optical zone is set at 9.0mm diameter/4.5mm radius, at 80% depth.

  1. Are these arcuate incisions designed to be opened at the time of surgery, or are they designed to be intrastromal?

Based on the published study and the experience of the physicians who have helped develop the formula, it is recommended to open all incisions at the time of surgery, and irrigate the opened incision with BSS.

  1. Why can’t I designate a phaco incision location other than temporal?

We believe that precision and consistency are key factors in achieving excellent results.  The temporal incision has been chosen because it is the most astigmatically neutral location for a phaco incision, and potentially reduces the posterior corneal against the rule astigmatism that is present in most corneas.  

  1. Why can’t I input my own SIA?

Surgically induced astigmatism is negligible for most surgeons using small incisions at a temporal location.  Additionally, a small amount of SIA has been accounted for by the internal aspects of the formula already.  If you are using a phaco incision of 2.75mm or less, the formula should work well. 

  1. Why are all incisions placed on the steep corneal axis and not adjusted for SIA using vector addition?

Given the very small SIA most surgeons create, in our experience, the steep axis is the most affective place for arcuate corneal incisions.  Vector addition is not always straightforward, and can lead to unpredictable results at times.

  1. Should I be inputting astigmatism measured by anterior keratometry or total keratometry?

Anterior keratometry was used to create this formula, and therefore we recommend it be the source for input into the formula.  Total keratometry may cause errors at this point.  We hope to update the formula in the future to include a total keratometry option.

  1. This formula seems to be aggressive.  Why?

This formula is based on the collective wisdom gained through the clinical experience of surgeons who have performed over 7,000 FLACS cases with arcuate incisions.  If it seems more aggressive than you are comfortable with, reduce the incisions as you wish.  However, please track your outcomes and decide for yourself if you are achieving the results that you want.

  1. Will this formula work for all femtosecond laser platforms?

Theoretically, this formula should work for all femtosecond laser platforms.  Outcomes have been verified on Catalys, LensAR and LenSX, however all platforms should work well so long as the optical zone and depth settings are as indicated and the incisions are opened and irrigated.  

  1. Will this formula work for all manual corneal arcuate incisions?

We believe that the precision of the femtosecond laser is impossible for the human hand to match.  However, if the optical zone and depth settings are as indicated and the incisions are opened and irrigated, the formula should also work with manual corneal arcuate incisions.