# "locationPlot" Function. Representation of a point from a reference (Mu chord, Kappa, vertex, etc)

This function draws, in a single angle plot, the data from a sample of points that can represent different information such as kappa angle or mu-chord, vertex normal, etc. The mean and standard deviation is computed and represented over the plot by means of a black point and an ellipse, respectively.

It has been reported that Kappa angle has an important role in laser refractive surgery techniques and placement of multifocal intraocular lenses (1). Anterior segment imaging devices report a 2-dimensional Cartesian displacement that roughly correlates with the concept of kappa angle.(2) Chang-Waring correctly addressed this issue and proposed the term chord mu (µ) or Chang-Waring chord (3) in order to avoid the misunderstandings generated by the literature. This function can represent the chord mu or any other reference points such as pupil center, vertex normal, kappa angle, lambda angle, etc. Any displacement from a reference point to a studied point can be represented by means of this function.

Matlab Toolbox “refractiveAnalysis” developed by Manuel Rodríguez-Vallejo for research purposes included in the version 1.0.0 the "locationPlot" function.

Below you have the help of the function. For more information about "refractiveAnalysis" Toolbox please Contact the author

```
% Creates a plot which includes a set of paired points from a sample.
%
% DESCRIPTION
%
% You can create any plot for describing mean and standard deviation of
% the centration of an IOL, angle kappa, pupil center, etc.
%
% PARAMETERS
%
% K Matrix of two columns. First column de magnitude of the X component of the
% vector from the reference (pupil, normal vertex, etc) and second column the Y.
% The plot is drawn considering (+) Nasal and (-)
% temporal for X component. (+) Superior and (-) Inferior to the reference.
% stepSector Step millimeters from the center for each vector.
%
% RELATED FUNCTIONS
%
% muPentacam
%
% RETURNS
%
% m Contains [mean, axis]
% SD Contains [SD at X, SD at Y]
%
% EXAMPLE
%
% [m,SD] = locationPlot(K, stepSector)
%
% VERSION
%
% 1.0.0
```

References

- Park CY, Oh SY, Chuck RS. Measurement of angle kappa and centration in refractive surgery. Curr Opin Ophthalmol. 2012;23(4):269-275.
- Chang DH, Waring GO. The Subject-Fixated Coaxially Sighted Corneal Light Reflex: A Clinical Marker for Centration of Refractive Treatments and Devices. Am J Ophthalmol. 2014;158(5):863-874.e2.
- Buehren T. The Subject-Fixated Coaxially Sighted Corneal Light Reflex: A Clinical Marker for Centration of Refractive Treatments and Devices. Am J Ophthalmol. 2015;159(3):611-612.