How to modify clinical refraction with topographic data-Kanellopoulos, MD 2016
Channel: LaserVision Ambulatory Eye Surgery Unit, Greece
Date: 2016-06-15

In this tutorial video Dr. Kanellopoulos explains hands-on (on the laser platform) the use of topographic data in order to modify the conventional refraction used up till recently.
Use of multiple refraction, corneal imaging, wavefront and topography-guided data in order to modify the refraction used in customized virgin-eye myopic LASIK
The topography-guided approach provides significant insight to the clinician in reconsidering what the actual correct refraction is for each patient.  For example, in a patient where the manifest dry and manifest wet refraction shows a small amount of astigmatism to be “confirmed” by a wavefront measurement and the topography measurement shows significant astigmatism, thus the topography-guided ablation suggests treatment of a much larger amount of astigmatism or, for example, a different axis of astigmatism, then this maybe puzzling for clinicians as far as what is the accurate correction for that patient.  
Some patients that we have been treating through the years with cornea-based laser refractive procedures may have dynamic lenticular astigmatism neutralizing their cornea astigmatism and at the same time becoming a bias to an accurate long term clinical refraction.  We therefore theorize that the most stable refraction would be the one based on cornea data, because the lenticular astigmatism is not stable and is probably astigmatism that is based on some level of accommodation and is likely to change through years to come. We have come to realize this principle with advanced lens-based refractive surgery and advanced cataract surgery, where the refractive error after the procedure is calculated as far as the astigmatism is concerned almost completely on the cornea parameters.