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Gongpu Lan, Kirill Larin, Michael D Twa; In vivo characterization of corneal natural frequency using optical coherence elastography. Invest. Ophthalmol. Vis. Sci. 2019;60(9):6826.
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Development of non-invasive, sensitive methods to characterize corneal biomechanics is significant for detection and treatment of corneal disease（e.g. keractoconus, collagen cross-linking, etc.). Here we described the use of optical coherence tomography (OCT) based elastography (OCE) to quantify the natural frequency of the human cornea in vivo.
Fourteen eyes were measured from seven human subjects with normal eyes. Central corneal thickness (CCT) and intraocular pressures (IOP) was measured using the Ocular Response Analyzer (Reichert Inc.). A short-duration (1ms), low-force (13Pa), localized (150μm diameter) air pulse system was used to stimulate the corneal apex. A home-built phase sensitive OCT imaging (spatial resolution: 0.24±0.07nm, temporal resolution: 50μs) was applied to capture the corneal response in a measurement grids of 26 (horizontal) × 11 (vertical) that covered an area of 2.5 mm × 2.5 mm, adjacent to the stimulation corneal apex (150µm). The natural frequency (NF) of corneal tissues was quantified using frequency analysis (FFT) of the resulting damped oscillatory tissue motions at each measured position.
The OCE measured NFs ranged from 236Hz to 273Hz with a variation (±STD) from ±5.7Hz to ±15.0Hz for each eye. NFs were positively correlated with higher IOP (from 11mmHg to 20.7mmHg); linear regression fit (y = 2.47x+215.7; R2=0.46). There was no correlation between NF values and CCT values over a wide range (486μm to 608μm).
The values of NF for the same eye remained constant within a 2.5mm2 area. The observed NF was greater with higher IOP. There was no observed correlation between NF and CCT. These results demonstrate the use of OCE to characterize oscillatory dynamic responses of the human cornea in vivo with potential clinical applications for quantitative determinations of corneal biomechanics and IOP.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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