Editorially independent content supported with advertising from
Surgically induced astigmatism (SIA) can be calculated easily using resources available at www.doctor-hill.com. On this website, Warren Hill, MD, has provided a spreadsheet that surgeons can fill in with preoperative and intraoperative parameters and then use to calculate their SIA. Alternatively, for most surgeons, a close value will be 0.10 D to 0.20 D of flattening at the temporal incision meridian.
SIA will vary between eyes and incision meridian. Of course, incision tunnel length and distance from the limbus can significantly affect the amount of flattening induced by a corneal incision.