Visualization of Schlemm’s Canal from 3D Reconstruction of UMB Images
Richard W. Helms, PhD; Faruk H. Orge, MD
Rainbow Babies and Children’s Hospital
Introduction: Ultrasound biomicroscopy (UBM) is widely used by ophthalmologists for visualizing anterior segment structures. Compared with other ophthalmic imaging modalities, UBM excels in its ability to penetrate opaque tissue and visualize structures such as Schlemm’s canal which cannot be seen through the lens.
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 volume of the anterior chamber extending peripherally beyond Schlemm’s canal. Those images are registered and filtered to highlight the canal and create a fully manipulable model.
Results: We have used this system to visualize anterior chamber structures, including Schlemm’s canal, in cadaver eyes, animals, and anesthetized patients. Image acquisition is completed in a few minutes and, depending on the level of image processing required, results are available to the surgeon in real time.
Discussion: Visualization of Schlemm’s canal is difficult because of its small size compared with the resolution of the UBM. However, under certain circumstances, our large datasets and extensive image processing are able to reveal the canal along with other, less elusive, anterior segment structures.
Conclusion: We have used ultrasound biomicroscopy to visualize Schlemm’s canal and other anterior segment structures in the laboratory and clinical settings. The ability to characterize these important structures promises to contribute significantly to research, 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