Automated Volumetric Measurement of Anterior Chamber and Other Structures and Iridocorneal Angle Based on 3D Reconstruction of UBM Images
Faruk H. Orge; Richard Helms
UH CMC and Rainbow B&C Hospital
Introduction: Ultrasound biomicroscopy is widely used by ophthalmologists to acquire 2D images of the anterior segment and to measure parameters such as the anterior chamber depth and iridocorneal angle. We present a system for automatic measurement of the angle and the anterior chamber volume based on 3D reconstruction of UBM images.
Methods: We use a Quantel 50 MHz UBM probe attached to the surgical microscope with a precision translation stage. Approximately 1000 slices are captured and reconstructed to create a 3D model of the anterior chamber. The 3D model is analyzed to quantify the anterior chamber volume and the IC angle.
Results: We have used our device to create 3D models of the eye in animals, cadaver eyes, and patients. Our software is able to perform automatic measurement of the AC volume and IC angle in these eyes and to provide those results in near real time.
Discussion: Our results are in quantitative agreement with other techniques including manual segmentation and angle measurements. Furthermore, because we capture the entire eye at fairly high resolution, our measurements do not rely on geometric simplifications or other approximations which could compromise the results.
Conclusion: We have demonstrated the use of 3D models from UBM images to measure anterior chamber parameters as the AC volume, segmentation of structures, accurate volumetric measurement of structures and the IC angle around the entire circumference of the eye. Other methods exist for making these measurements, however, the combination of the UBM resolution and its ability to penetrate opaque lenses makes it a unique tool for clinicians. |This promises to be a valuable tool for diagnosis and treatment planning.|
References: Kirchhoff A, Stachs O, Guthoff R. Three-dimensional ultrasound findings of the posterior iris region. Graefes Arch Clin Exp Ophthalmol. 2001;239(12):968-71.