Three-dimensional display of the ocular region. Improvement of scanning method

Abstract

A new system was developed to display in three-dimensional fashion the interior of the eyeball and to calculate the volume of an intraocular mass. In this system, sampling of echowaves is performed by a spirally scanning transducer covering the area from the central axis to the periphery of the eyeball. Using this system, scanning of the entire eye can be completed within four minutes compared with the former method of piling up cross-sectional layers. Echo waves were digitized to 256 grades and were stored on a floppy disk with the space positions noted. This rapid sampling is advantageous since it minimizes spacial displacement, which is the major cause of decreased sharpness of three-dimensional displays on CRT and of errors in measuring volumes of intraocular space or mass. To display a three-dimensional view of the desired intraocular surface from a given direction on CRT, brighter color is given to the layers closer to the surface and each layer is intensity-graded using a black and white system. To measure volume, an image-processing method of smoothing and a Laplacian process were applied to the surface with the aid of a microcomputer, and the inner pixels of the closed space were counted. This three-dimensional mode of display provides an overview of the shape and the extent to which the tissues of interest are involved. It is also especially helpful in cases with opacification of the ocular media.