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Aphrodite Dracopoulos, Inka Tertinegg, John G. Flanagan; Measurement Of Intraocular Pressure (IOP) From The Scleral Surface: A Proof-of-concept Study For The Development Of A Continuous IOP Monitoring Device. Invest. Ophthalmol. Vis. Sci. 2011;52(14):670.
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To investigate the efficacy of measuring scleral deformations to indirectly measure IOP change in porcine eyes.
Eight porcine eyes were obtained within 48 hours post mortem from a local abattoir. A pre-wired strain gage sensor (Omega Engineering, Inc., Stamford, CT) was mounted to the conjunctiva only in two eyes and then directly to the sclera in the superior temporal region of the eye. The anterior chamber was cannulated using a 27-gauge needle introduced from the temporal limbus and connected to a 30ml syringe filed with degassed water on a stand with variable height. Another 27-gauge needle was inserted into the anterior chamber through the nasal limbus primed with degassed water and connected to a pressure transducer. Adjusting the height of the syringe generated IOP changes and was recorded with a commercial software program (TracerDAQTM Software, MicroDAQ.com Ltd., Contoocook, NH). IOP was increased in increments of 10 mmHg from 0 to 50 mmHg (± 1.0 mmHg) and the surface deformation of the strain gage sensor was recorded for each incremental step.
IOP and surface deformation of the strain gage sensor increased linearly with increasing volume. Analysis of variance gave a significant difference between X and Y (p<0.0001) with rho values ranging from 0.728 to 0.870 when mounted directly to the conjunctiva and 0.994 to 0.999 when mounted directly to the sclera.
Changes in IOP can be accurately assessed by measuring changes in the radius of curvature of the sclera. These results provide a proof-of-concept for the realization of a sensor to monitor IOP. The ability of a strain gage sensor to determine conjuntival and/or scleral deformation could be a novel, non-corneal approach to the measurment of 24 hour IOP.
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