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Yann Bouremel, Christin Henein, Steve Brocchini, Peng Tee Khaw; Intraocular Pressure (IOP) effects on self-sealing clear corneal incisions using 3D printed anterior segment model. Invest. Ophthalmol. Vis. Sci. 2019;60(9):1016. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Sutureless clear cornea cataract surgery is the preferred method for most ophthalmic surgeons,facilitated by foldable IOLS. However, in different situations such as intraocular pressure variation including hypotony and softer eyes (e.g children and collagen abnormalities) may lead to leakage and other complications such as hypotony and intraocular infection. The effects of IOP on incision sealing and leaking mechanisms have not yet been studied. A 3D model of the anterior segment was developed to determine the biomechanical effects of intraocular pressure on self-sealing and leaking corneal incisions.
A silicone cornea (Young’s Modulus: 1.25-4.21 MPa) of different thicknesses (0.2-0.5 mm) and diameters (5-20 mm) is clamped to a 3D printed anterior segment model and connected to a microfluidic set-up. The flow rate and pressure recorded every second. An incision (1mm long; 0.2 mm wide) was made centrally in the simulated cornea using a micro feather blade. Simulated IOP was increased up to 140 mmHg in steps of 1.5 mmHg or more every hour. Simulations using finite element modelling (Abaqus) were created to map the distribution of Von Mises Stress (σ) and the strain (ε) in the meridian and circumferential directions along the different corneas for different IOPs.
Self-sealing incisions leak at a higher pressure with increasing corneal thickness (T), with increasing elasticity (Young’s Modulus, E) and with decreasing corneal diameter (D). Higher pressure corresponds to the cornea having to be subjected to a higher stress to open a self-sealing incision. A typical simulation of the corneal stress is shown in Figure 1. The strain (ie. enlargement) at the point of incision when the leak starts was 2.8 ± 0.5% in all cases, with a flow rate of 0.4±0.2 µl/min. Greater enlargements from higher IOPs resulted in higher flow rates (Figure 2). In this model, as strain ε = 8/3 (H/D)2 where H is the central corneal height, the spontaneous incision leak occurs when H>0.1D after injection.
Using a 3D printed anterior segment model, geometrical and material properties can be adjusted individually to study self-sealing incisions in detail. Incisions in large and thin corneas with lower elasticity are more susceptible to leak at lower pressures.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
Distribution of stress along a silicone cornea.
Incision leak rate of silicone corneas with different elasticity.
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