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Han Saem Cho, Seung Hyen Lee, Heung Soon Lee, Heh-Young Moon, Sae Chae Jeoung; Fabrication of model eye to mimic human eye for assessing tonometer pressure. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1414.
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© ARVO (1962-2015); The Authors (2016-present)
Intraocular pressure (IOP) is usually estimated by a tonometer based on the Imbert-Fick law. Systematic investigation for the effect of the geometrical and mechanical characteristics of eye phantom on the validity of the tonometer pressure is rare. We fabricated artificial eye phantoms of which 3-D geometries and mechanical properties were tailored to those properties of human eye and applied to evaluate the validity of tonometer pressure.
Optically transparent eye phantom filled with a liquid (Fig. 1(a-b)) was made of polydimethylsiloxane (PDMS) based on Archimedes principle. PDMS pre-polymer and curing agent were mixed, degassed, and poured into the mold. After pre-curing, aqueous glycerol solution was carefully injected. PDMS mixture was fully cured at 80 celsius for 2 hours. The shell thickness at the center as well as the mechanical modulus was controlled by the concentration of ethylene glycol and the formulation of PDMS, respectively. Three different types of mold were used to reflect the range of human corneal diameter and curvature. Optical coherence tomography and air-puff tonometer were used to determine the detailed geometrical information of eye phantom and tonometer pressure, respectively.
The thickness of the shell at the centre of model eye could be varied from 0.2 mm to 1.0 mm with different modulus. (Fig. 1(c)) The range of model eye properties is comparable to the typical values of the modulus and the thickness of human eye of 0.4 MPa and 0.52 mm, respectively. The shell thickness increases progressively towards the limbus. The tonometer pressure was found to be dependent on the shell thickness as well as the modulus of the shell. (Fig. 1(d))
We have successfully developed eye phantoms for evaluating the validity of tonometer pressure. The values measured from eye phantoms are similar to the typical IOP of human eye if the modulus and thickness of the shell are similar to those of human eye. In the presentation, we will further discuss the long-term stability of the eye phantom.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Figure 1 Eye phantom (a) and its 3-D shape (b). Shell thickness as a function of glycerol concentration (c).
Figure 2 Fabrication of PDMS eye phantom
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