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Kirill Larin, Achuth Nair, Manmohan Singh, Salavat Aglyamov, Michael D Twa; Heartbeat OCE: Corneal Biomechanical Response to Heartbeat Pulsation. Invest. Ophthalmol. Vis. Sci. 2020;61(7):4714.
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© ARVO (1962-2015); The Authors (2016-present)
Analyzing the biomechanical properties of the cornea can be a useful method for detecting several ocular diseases and monitoring therapeutic interventions. Optical coherence elastography (OCE) is an emerging new technique to assess the mechanical properties of the cornea. Typically, OCE are used to measure the corneal response to an external force. Here we demonstrate capability of OCE to measure the corneal biomechanics in response to spatially varying fluctuations in IOP due to the heartbeat.
Measurements were performed in 10 ex vivo porcine eye globes and 5 in vivo in rabbits. During ex vivo measurement the eye globe was placed into a custom eye holder and cannulated with two syringes for IOP control. IOP was sinusoidally pulsed with an average pressure of 10 mmHg using a closed loop control system consisting of a syringe pump and a pressure transducer. Crosslinking (CLX) was performed in ex vivo experiments to induce mechanical contrast. A common-path SD-OCT system with 6 µm axial resolution, 50 kHz line rate, and ~2 nm displacement sensitivity was used to detect the small displacements in the cornea induced by IOP fluctuation. Axial strain was calculated from displacement using a linear regression-based method.
Average displacement within the cornea ranged from -1.6 ± 0.5 µm to 0.9 ± 0.3 µm, suggesting that there is an overall compression at the anterior of the cornea and relaxation at the posterior of the cornea over the entire pulse. CLX was significantly reducing depth-depended response, indicating increased stiffness. While we yet to quantify corneal mechanical properties, these data clearly suggest mechanical gradient through the cornea.
In this work, we show preliminary data for analyzing the biomechanical properties of the cornea during dynamic intraocular pressure changes followed the ocular pulse and CLX procedure. Our work suggests that corneal strain varies axially during pulsatile IOP fluctuation. Future work will consider changes in mechanical properties at different baseline IOPs and will include quantitative metrics to assess elasticity. The results shown here suggests that corneal biomechanics can be measured in vivo without the need for external excitation.
This is a 2020 ARVO Annual Meeting abstract.
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