A new coordinate system convention in schematic eye modeling.
OBJECTIVE
To discuss standardizing methods for presenting results from schematic eye calculations where light is entering the eye and forming an image on the retina.


METHODS
Published methods, measurement equipment, and software were evaluated.


RESULTS
The methods already used by ray tracing software are proposed, where everything is viewed from behind the eye and a conventional (x,y) coordinate system is used for images and plots. For meaningful evaluation in comparison to the image, any representations of the cornea, pupil, imaging wavefront, point spread function (PSF), and spot diagram are rotated by 180° about the optical axis for display to match the image orientation of a standard text chart. If a Zernike sag surface is used for a corneal surface of a schematic eye, this is also defined from the rear; however, care must be taken to ensure that the ordering of the Zernike terms is correct.


CONCLUSIONS
Simulated images can be viewed from behind the eye and oriented so that text has a normal appearance. This requires a rotation of the imaging wavefront and PSF by 180° about the optical axis.
Alcon Laboratories Inc., Ft Worth, Texas 76134, USA. mike.simpson@alconlabs.com
Michael J
MJ
Simpson
D006801:Humans; D008027:Light; D008954:Models, Biological; D012160:Retina / Q000528:radiation effects*; D014785:Vision, Ocular / Q000502:physiology*