Sub-micrometer axial resolution OCT for in-vivo imaging of the cellular structure of healthy and keratoconic human corneas

Abstract

Abstract:Corneal degenerative conditions such as keratoconus (KC) cause progressive damage to the anterior corneal tissue and eventually severely compromise visual acuity. The ability to visualize corneal tissue damage in-vivo at cellular or sub-cellular level at different stages of development of KC and other corneal diseases, can aid the early diagnostics as well as the development of more effective treatment approaches for various corneal pathologies, including keratoconus. Here, we present the optical design of an optical coherence tomography system that can achieve 0.95 µm axial resolution in biological tissue and provide test results for the system's spatial resolution and sensitivity. Corneal images acquired in-vivo with this system from healthy and keratoconic human subjects reveal the cellular and subcellular structure of the corneal epithelium, as well as the normal and abnormal structure of the Bowman's membrane and the anterior corneal stroma.

Comparison between a supercontinuum source and a titanium sapphire laser in achieving ultrahigh resolution spectral domain optical coherence tomography (SD-OCT)

“…All corneal layers, as well as the tear film can be resolved via both the Ti:Sapphire and the supercontinuum source. Both sources are suitable for ultrahigh resolution corneal OCT imaging, visualization of the precorneal tear film and evaluation of the tear film thickness and show potential for the diagnosis and treatment monitoring of various corneal pathologies [10,11].…”

Selective Retina Therapy

“…Although modern OCT systems can scan remarkably faster (>1 MHz depth scan rate, being <1 μs exposure time per depth scan) along with a reduction of temporal resolution of the lateral scan, the 4 orders of magnitude faster shockwaves induced by a short treatment pulse in the sub 10 μs scale cannot be directly resolved in an 2D image. This becomes even more restricting in typically slower ultrahigh-resolution systems with a spectral bandwidth of more than 100 nm that supports an in vivo axial resolution of about 3 μm or below, which is required for clear visualization of cellular structures in the RPE layer and differentiation from its surrounding tissue [84]. During a burst of successive pulses, optical reflectance from the irradiation laser increases in signal strength.…”

Enhancement of morphological and vascular features in OCT images using a modified Bayesian residual transform

“…The human cornea imaging study was approved by the Research Ethics Committee at the University of Waterloo and adhered to the tents of the declaration of Helsinki. The human corneal OCT images were acquired with a fiberoptic, SD-OCT operating in the 800 nm spectral range, that provided ~0.95 µm axial and ~4 µm lateral resolution in corneal tissue at 34,000 A-scan/s image acquisition rate [45]. Cross-sectional images (1000 Ascan × 4096 pixel/Ascan) were acquired in-vivo from the corneas of healthy human subjects.…”