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Antoine Ramier, Behrouz Tavakol, Seok Hyun Yun; Effect of intraocular pressure on the vibrational resonance of the cornea measured by optical coherence tomography. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4326.
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We have previously reported the observation of corneal vibrational modes by using sound-coupled optical coherence tomography (OCT). This vibrography technique has a potential to measure corneal stiffness, which plays important roles in keratoconus, corneal crosslinking, and refractive surgery. As in air-puff corneal tonometer, the vibrational resonance of the cornea is thought to be sensitive to intraocular pressure (IOP), but this dependence has not been studied quantitatively. We have investigated the effects of IOP on the resonance modes of sound-induced corneal vibration.
OCT vibrography was performed on freshly enucleated bovine eyeballs, which were connected to a water column to control the IOP level between 10 and 25 mmHg. A custom-built, sound delivery device applied monotone or frequency-chirped sound waves onto the cornea at sound pressure levels (SPL) of 80-110 dB. The amplitude and phase of vibration of the cornea over a sound frequency range from 50 to 500 Hz were measured by using a phase-sensitive OCT system.
The fundamental resonance mode was observed at a sound frequency of about 130 Hz. The amplitude of vibration scaled linearly with sound pressure and was on the order of 10nm/Pa at the resonance. Increasing IOP results in a shift of the resonance peak towards higher frequencies, and reduces the vibrational amplitude of the resonance. Cycling the IOP back to lower pressures showed no noticeable hysteresis.
The IOP level significantly affects the vibrational resonance modes of the cornea. This finding indicates that IOP is an important factor to consider for the measurement of corneal stiffness from corneal resonance analysis and implies that OCT vibrography may have a potential for IOP measurements.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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