How to quantify astigmatism correction after refractive surgery
To assess the success of the spherical correction after refractive surgery you just need the sphere pre-op and post-op to make the calculations, usually this is done with the spherical equivalent (SE) to take into account the astigmatism although we all now that the same SE can have very different visual acuity result depending on the astigmatism.
I will show here how to calculate the success of astigmatism after refractive surgery using the demo version of Refractive Surgery Graphics (RSG) which is free for up to 20 eyes.
RSG assumes that the target cylinder is 0.
If you are interested in the calculation details and astigmatism vector analysis here is a link to the paper by Alpins and Goggin.
Now let's get to work and make the excel file:
- Get refractive cylinder and axis pre-op and post-op for 20 eyes.
- The first row is for the headers, fill whatever you want from column A to T, but don't leave them empty. When you upload the excel this will be changed.
- Now we will fill the next 20 rows like this:
Column D: cilinder pre-op
Column E: axis pre-op
Column K: cilinder post-op
Column L: axis post-op
- Save your excel file.
Go to the demo website of RSG here, click on the button Choose File and choose the excel you just made, you will then see your excel with the cylinder and axis pre-op and post-op in the correct place.
Now click in the tab at the top Standard graphs for reporting outcomes -> Astigmatism
You will see here the three standard graphics for reporting outcomes related to astigmatism and at the bottom right you will see some coefficients, one of them is Success of astigmatism surgery, that is what we were looking for !
Note that if the cylinder post-op is larger than the cylinder pre-op, the success percentage could be negative, RSG will make the percentage in those cases 0 %
If you have any problem uploading, leave a comment.