Abstract
Corneal biomechanics play a fundamental role in the genesis and progression of corneal pathologies, such as keratoconus; in corneal remodeling after corneal surgery; and in affecting the measurement accuracy of glaucoma biomarkers, such as the intraocular pressure (IOP). Air-puff induced corneal deformation imaging reveals information highlighting normal and pathological corneal response to a non-contact mechanical excitation. However, current commercial systems are limited to monitoring corneal deformation only on one corneal meridian. Here, we present a novel custom-developed swept-source optical coherence tomography (SSOCT) system, coupled with a collinear air-puff excitation, capable of acquiring dynamic corneal deformation on multiple meridians. Backed by numerical simulations of corneal deformations, we propose two different scan patterns, aided by low coil impedance galvanometric scan mirrors that permit an appropriate compromise between temporal and spatial sampling of the corneal deformation profiles. We customized the air-puff module to provide an unobstructed SSOCT field of view and different peak pressures, air-puff durations, and distances to the eye. We acquired multi-meridian corneal deformation profiles (a) in healthy human eyes in vivo, (b) in porcine eyes ex vivo under varying controlled IOP, and (c) in a keratoconus-mimicking porcine eye ex vivo. We detected deformation asymmetries, as predicted by numerical simulations, otherwise missed on a single meridian that will substantially aid in corneal biomechanics diagnostics and pathology screening.
Highlights
Corneal biomechanics, corneal morphology, and intraocular pressure (IOP) are some of the most important factors influencing the balance of forces that help maintain a healthy eye and good vision [1]
We show that our system can detect corneal deformation profiles and deformation asymmetries due to localized changes in biomechanical properties, as predicted by finite element analysis (FEA), that are useful for corneal biomechanics diagnostics and pathology screening
This result shows the importance of measuring corneal deformation to air-puff excitation on multiple meridians, confirming the premises that a multi-meridian instrument is required for better differentiating an early-keratoconic cornea from a healthy one
Summary
Corneal morphology, and intraocular pressure (IOP) are some of the most important factors influencing the balance of forces that help maintain a healthy eye and good vision [1]. The measurement accuracy of the IOP, a glaucoma biomarker, is influenced by corneal biomechanical properties [5]. Keratoconus is a progressive, non-inflammatory disorder resulting in thinning and protrusion of the cornea into a conical shape [2]. It is believed that changes in biomechanical properties take place prior to corneal thinning and steepening [3], in what is known as pre-clinical keratoconus. Keratoconus treatments [8] include, among others, collagen cross-linking for corneal stiffening and intrastromal corneal ring segment implants for flattening the cone, in mild to moderate cases, and corneal transplant in more advanced cases. Treatments will benefit from an early detection, prior to the development of changes in corneal shape
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