METHODS TO OBTAIN QUANTITATIVE PARAMETRIC DESCRIPTIONS OF THE OPTICAL-SURFACES OF THE HUMAN CRYSTALLINE LENS FROM SCHEIMPFLUG SLIT-LAMP IMAGES - I - IMAGE-PROCESSING METHODS

Of the methods developed (e.g., phakometry, magnetic resonance imaging , etc.) for noninvasive measurement of the geometry of the anterior se gment of the human eye, Scheimpflug photography offers the best resolu tion and the highest precision. The primary obstacle encountered with this or any other image-based method has been in obtaining quantitativ e measurements directly from the images. Image enhancement !gray-scale gradient analysis) and pattern recognition methods (Hough transform a nd recursive least-squares algorithms) are developed so that parametri c representations of lens surfaces and zone boundaries can be obtained directly from the images. Methods to correct for nonlinear Scheimpflu g camera reproduction ratios and provide error estimates for geometric al parameters are also developed and will be presented separately. Com bined, these techniques yield representations of lens geometry having sufficient precision, to which paraxial ray tracing can be applied to determine lens optical properties by using well-posed optical models w ith one unknown. (C) 1998 Optical Society of America.