High-Speed Optical Coherence Tomography of Anterior Segment Surgical Anatomy and Pathology

Abstract

Abstract: : Purpose: To use a high-speed corneal and anterior segment optical coherence tomography (CAS-OCT) system to image ocular pathologies and surgical anatomy. Methods: A high-speed (4000 a-scan/sec) wide-field (16 mm) CAS-OCT system was developed. It uses a longer wavelength (1.3 microns) compared to retinal OCT systems (0.8 microns). OCT scans were performed on 11 eyes with anatomic features of interest. Results: OCT of post-surgical cornea (LASIK, penetrating keratoplasty), trabeculectomy bleb, anterior chamber intraocular lens (IOL), iris masses and cataract were obtained. Full-thickness imaging of sclera, angle and iris was possible. No appreciable motion artifact was noted at 8 frames/sec. The entire LASIK flap could be fully visualized. In keratectasia, OCT showed relative corneal thinning in the area of steepening. Causative factor such as inadequate residual posterior stromal thickness and excessive flap thickness could be quantitatively assessed. The longer 1.3-micron wavelength allowed the angle recesses to be visualized. The recess-to-recess anterior chamber width could be directly measured, along with other parameters such as the anterior chamber depth and crystalline lens vault. In trabeculectomy images, the sclerotomy site could be visualized as well as the whole bleb anatomy. The anterior chamber IOL were seen and the footplates position were recorded. Iris and ciliary body masses could be precisely delineated and accurately measured. Conclusions: The CAS-OCT prototype allowed non-contact visualization and measurement of corneal and anterior segment pathologies and surgical anatomy. The high speed allows quantitative measurements of relevant biometric dimensions. The longer wavelength (1.3-micron) allows greater penetration through highly scattering tissue such as limbus and sclera.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, S • refractive surgery: LASIK • anatomy