Correcting Pentacam chord-mu for conventional notation
Updated on version: 1.0.3


This function corrects the Kappa or chord-mu obtained from Pentacam in order to move the center of coordinates to the pupil center instead of the vertex normal. Furthermore, it corrects the differences of sign from right and left eyes in order to combine both eyes in the same plot.


Correcting Pentacam chord-mu for conventional notation


It is important to note that Pentacam does not represent the mu-chord in conventional notation. It is known that Kappa angle is positive when the vertex normal is Nasal to the pupil center and negative when vertex normal is Temporal to the pupil. This convention of signs is not followed for the Pentacam reporting of chord-mu, therefore, it is required a conversion to the conventional sign notation. Furthermore, the signs change from left and right eyes. Therefore, it is required to correct the signs before combining right and left eyes in the same sample.


  1. Rodríguez-Vallejo M, Piñero DP, Fernández J. Avoiding misinterpretations of Kappa angle for clinical research studies with Pentacam. J Optom. April 2018. 

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