Scheimpflug image-processing method for accurate measurement of ocular surfaces.
OBJECTIVE
To develop a method to process Scheimpflug images to estimate higher-order variations in ocular surfaces.


METHODS
New England College of Optometry, Boston, Massachusetts, USA.


METHODS
Zernike polynomial functions were used rather than lower-order surface functions to fit the ocular surfaces to evaluate higher-order variations. A related ray-tracing method was developed to correct optical distortion of the Scheimpflug image.


RESULTS
The new method to process Scheimpflug images showed higher-order variations in the posterior corneal surface. In a simulation, ignoring higher-order variations in the anterior corneal surface, as in previous studies, produced an error as high as 202% for some estimated Zernike coefficients of the posterior corneal surface.


CONCLUSIONS
The results indicate that it is necessary to correct refractive distortion in Scheimpflug images using higher-order surface functions and that the method developed in this study can be used to process scheimpflug images for measurement of ocular wavefront aberrations.
He
Ji C
JC
New England College of Optometry, Boston, Massachusetts 02115, USA. hej@neco.edu
Fang
Yanwen
Y
D003315:Cornea / Q000033:anatomy & histology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D015233:Models, Statistical; D008962:Models, Theoretical; D010781:Photography / Q000295:instrumentation*