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Spectral analysis of ocular pulse amplitude recordings obtained using a contact lens sensor
Author(s) -
HIRN C,
RUSSELL RA,
LAMPARTER J,
LASCARATOS G,
HO T,
GARWAYHEATH DF
Publication year - 2013
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/j.1755-3768.2013.2727.x
Subject(s) - fast fourier transform , amplitude , optics , ophthalmology , correlation , medicine , mathematics , physics , algorithm , geometry
Purpose The aim of this study was to investigate whether the ocular pulse amplitude (OPA) can be detected in fluctuation curves recorded with the Sensimed Triggerfish® Sensor (TS), and analysed by Fast Fourier Transform (FFT). Methods 40 subjects (20 open angle glaucoma [OAG], 20 healthy) underwent one hour of TS monitoring. Intraocular pressure and OPA were measured by dynamic contour tonometry (DCT) and DCT OPA was used as the reference. Segments of TS OPA fluctuations were visually identified (VI), and the amplitude (mVequ) was measured (VI‐TS OPA). In addition, FFT signal analysis, which reduces a periodic function into its frequency components, was performed on VI segments, and the amplitude (arbitrary units [AU]) of the fundamental measured (FFT‐TS OPA). The correlation between VI‐ and FFT‐TS OPA was investigated. VI‐ and FFT‐TS OPA were compared with DCT OPA. Results In 3 subjects, TS recording failed. In 8 subjects, either no OPA or no fundamental could be identified. For the remaining 29 subjects (13 OAG, 16 healthy), both mean (±standard deviation) VI‐ and FFT‐TS OPA were lower in OAG (9.0±3.9mVequ and 184.6±303.7AU) than in healthy subjects (10.2±4.5mVequ and 303.3±292.0AU). Mean DCT OPA was higher in OAG (2.7±0.8mmHg) than in healthy subjects (2.3±0.6mmHg) (p>0.05 for all). There was a significant correlation between VI‐ and FFT‐TS OPA (Spearman's rho=0.84; p<0.0001). In OAG subjects only, the correlation between VI‐TS OPA and DCT OPA (Spearman's rho=0.52, p=0.072) and FFT‐TS OPA and DCT OPA (Spearman's rho=0.48, p=0.099) approached significance. Conclusion It is possible to identify OPA in TS fluctuation curves and to analyse OPA by FFT. There is a weak association between TS OPA and DCT OPA in OAG.