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Ewa Celina Maczynska, Karol Marian Karnowski, Bartlomiej Kaluzny, Ireneusz Grulkowski, Maciej D Wojtkowski; Assessment of biomechanical properties of porcine corneas with air-puff swept source OCT. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2391. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
A novel approach to assess Intraocular Pressure (IOP) and/or specific biomechanical properties of the cornea were proposed. Biomechanical properties of the porcine corneas ex vivo at well-controlled levels of the intraocular pressure, and the impact of cross-linking (CXL) on corneal biomechanics were studied.
Thirty fresh, enucleated porcine eyes were measured with high-speed swept source Optical Coherence Tomography (SS-OCT) instrument combined with the air-puff chamber for non-contact generation of corneal deformation. Data acquired from corneal apex during deformation-recovery process together with the reference pressure value enabled generation of corneal hysteresis representing viscoelastic properties of the cornea (Figs.1A-B). The corneal response to the air pulse was determined for ascending (5 to 35 mmHg) and descending (from 35 to 5 mmHg) IOP levels. Later on, the corneal response to the air pulse before and after CXL procedure under constant IOP condition was measured. In all cases, the parameters of recorded hysteresis loops (applied pressure vs. deformation amplitude) were analyzed.
Air-puff SS-OCT measurements enabled to calculate corneal hysteresis loop parameters such as the hysteresis curve area or maximum deformation amplitude. The corneal hysteresis area became lower with ascending IOP value (Fig. 1B). Additionally, viscoelastic behavior of ex vivo porcine corneas was manifested as a difference in the hysteresis area measured for ascending and descending IOP values (Fig. 1C). There was a statistically significant correlation between hysteresis area and maximum deformation amplitude (R=0.99, p=0.001) (Fig. 1D). The central corneal thickness drops immediately after CXL procedure (p=0.05) (Fig. 2A). CXL made the corneas more stiff resulting in lower hysteresis area values (Figs. 2B-C).
OCT combined with the air-puff gives additional information about IOP and biomechanical properties of pig eye ex vivo. Further development of this method has potential of being used as a tool for minimally invasive assessment of IOP and central biomechanical properties in healthy and diseased eyes in humans.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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