Abstract
We present imaging of corneal pathologies using optical coherence tomography (OCT) with high resolution. To this end, an ultrahigh-resolution spectral domain OCT (UHR-OCT) system based on a broad bandwidth Ti:sapphire laser is employed. With a central wavelength of 800 nm, the imaging device allows to acquire OCT data at the central, paracentral and peripheral cornea as well as the limbal region with 1.2 µm x 20 µm (axial x lateral) resolution at a rate of 140 000 A-scans/s. Structures of the anterior segment of the eye, not accessible with commercial OCT systems, are visualized. These include corneal nerves, limbal palisades of Vogt as well as several corneal pathologies. Cases such as keratoconus and Fuchs's endothelial dystrophy as well as infectious changes caused by diseases like Acanthamoeba keratitis and scarring after herpetic keratitis are presented. We also demonstrate the applicability of our system to visualize epithelial erosion and intracorneal foreign body after corneal trauma as well as chemical burns. Finally, results after Descemet's membrane endothelial keratoplasty (DMEK) are imaged. These clinical cases show the potential of UHR-OCT to help in clinical decision-making and follow-up. Our results and experience indicate that UHR-OCT of the cornea is a promising technique for the use in clinical practice, but can also help to gain novel insight in the physiology and pathophysiology of the human cornea.
Highlights
The integrity of the cornea and the ocular surface is essential for normal vision
We show images of various corneal pathologies taken by a custombuilt ultrahigh-resolution optical coherence tomography (OCT) system with a resolution of approximately 1.2 μm and discuss possible implications for the use of this device in clinical practice
The first one at the input of the interferometer allows to set the probe beam power according to the maximum permissible exposure (MPE) limits as specified by the International Electrotechnical Commission (IEC 60825-1) [41] and by the American National Standard for Safe Use of Lasers (ANSI Z136.1) [42] and to optimize the signal that arises from the sample and is detect by the spectrometers CCD camera
Summary
The integrity of the cornea and the ocular surface is essential for normal vision. Globally, corneal disease is a major cause of blindness including a wide variety of infectious, inflammatory and hereditary disorders [1, 2]. The cornea is examined using slit lamp biomicroscopy at various magnifications. Different lighting regimen such as diffuse illumination, focal illumination, indirect illumination and retroillumination can be used to further differentiate tissues and layers. Placido-disk based keratoscopy is based on looking into the reflected image from the corneal surface of an object composed of multiple discs. Slitscanning elevation topography combines the principles of Placido-disk based keratoscopy with those of slit scanning providing measurements of anterior and posterior curvature as well as mapping the structure of the cornea [4]. Modern instruments employ rotating Scheimpflug cameras that take multiple slit-images and allow for quantification of corneal elevation, curvature, and thickness [5]. Using very high frequency it is possible to do multi-layered pachymetry [6]
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