I'm going to process Placido disk raw images from a costum corneal topography. I have processed the images and calculated the axial map. Can you give me some suggestions, or better a matlab code, how to calculate the instantaneus tangential map from the axial curvature map? thanks in advance
Call Fabrice, like us he is working from home and will be happy to see you are still doing research projects!
Thanks Jean-Marie Parel, could you share the contacts of Mr Fabrice? thanks in advance.
Hi G. Lombardo could you please help out with the Axial Map generation. We too have raw placido based images.
If there is some relevant publication or open-source code that could be used, it would be very helpful.
Thanks!
Ciao Siddhartha Gairola ! You can use this nice "APPLIED OPTICS - Vol. 52, No. 7,C24-C29 ( 2013) in which you will find a method to derive AXIAL MAP and a preliminary open access routine. My suggestion it is to develop a robust routine to exctract the "placido rings" from your images (so the images should be fine) and then you need to acquire the placido rings from "sphere" within known curvature (you need at least 4/5 sphere of curvature ranging from 6-9 mm). Then I find a nice publication how to derive instantaneous/tangetial map from axial map. It is "Axial and Instantaneous Power Conversion in Corneal Topography" of Stanley A. Klein. I hope I have been of help.
G. Lombardo Thank you Sir for your help :)
I have taken a look at the following resource "Open-access operating algorithms for commercial videokeratographer and improvement of corneal sampling" by Julián Espinosa, David Mas, Jorge Pérez, and Ana Belén Roig.
Am now working on understanding it. Thanks a lot :)
Hi G. Lombardo the Axial map generation algorithm works well with the calibration step.
Did you figure out a way to generate the Tangential (Curvature) Maps?
I am trying to compute the instantaneous radius at each point using curve fitting. But that doesn't seem to work very well.
Ciao Siddhartha Gairola , I follow the step described in "Axial and Instantaneous Power Conversion in Corneal Topography" of Stanley A. Klein to derive the tangential curvature. Now I'm goindo to study arc-step method to have a more realiable tangential map. I wish you a nice day.
Ciao G. Lombardo , thank you for your help. Does the "Axial and Instantaneous Power Conversion in Corneal Topography" work well?
Also, the paper related to "Arc-Step Method" is not public. Could you please point to a paper or resource that explains this method well?
Thanks. Wishing you a good day ahead.
Hi Siddhartha Gairola I have implemented the algorithm to retrieve the instantaneous tangential curvature from axial and it seems it works fine. You need to "smooth" the result in order to have a realiable map. For arc-step method I m going to study the public article that are published. I'm just studying the method.
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