Spectral content of the intraocular pressure pulse wave: glaucoma patients versus normal subjects

2006

Eye

Purpose To study the naturally occurring kinetic characteristics of corneal surface. Methods The right eyes of three subjects (young, early presbyope, and presbyope) were examined. Cardiac signal and longitudinal corneal apex movements were simultaneously measured with electrocardiography (ECG) and a high-speed videokeratoscope, respectively. Time, frequency, and combined timefrequency representations of the acquired signals were derived to establish their temporal and spectral contents. Coherence analysis was used to assess the correlation between the corneal apex velocities and the cardiopulmonary system. Results In all measurements, longitudinal corneal apex velocity signals showed close correlation with the corresponding ECG signals. The signatures of the pulse frequency, which was inferred from the ECG spectra and their variations in time, were clearly visible in the spectral content of corneal apex velocities. For the young subject, the correlation was the strongest and all of the spectral content of the pulse signal including the harmonics was propagating to the corneal apex velocities. For the other two subjects, there was a clear propagation of the pulse signal itself but not of all pulse harmonics. Conclusions Longitudinal movements of the corneal apex are closely related to the cardiopulmonary system. The differences in propagation of pulse harmonics to the corneal apex velocities for different subjects suggest that the frequency characteristics of apex velocity could be related to pulsative variations in the intraocular pressure and biomechanical properties of the eye. These findings could potentially be used in noninvasive assessment of the hemodynamic status of the eye with high-speed videokeratoscopy.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Spectral characteristics of longitudinal corneal apex velocities and their relation to the cardiopulmonary system

Kasprzak

2006

Eye

“…The expansion of the corneal and scleral surface is mainly caused by the ocular pulse, which depends also on heart activity [3,4]. The results obtained by Evans showed that amplitudes of the ocular pulse for healthy and glaucomatous patients, calculated using spectral analysis, are different [5]. Therefore, examining the relationships between the ocular pulse and cardiovascular activity might bring information about blood propagation to the eye globe.…”

mentioning

confidence: 99%

Analysis of ocular hemodynamic using combined STdOCT and ultrasonic methods

Danielewska

Szlag

et al. 2011

Photon. Lett. Poland

“…Measurement of ocular pulse amplitude was used to diagnose carotid occlusion [3]- [5] and visual field defects [6]. Examination of the ocular pulse spectral content found to be a potential diagnostic tool in glaucoma [7]. corneal surface pulsation and cardiovascular system activity [8]- [10].…”

Section: Introductionmentioning

confidence: 99%

Ultrasonic In Vivo Measurement of Ocular Surface Expansion

Kowalska

Kasprzak

IEEE Trans. Biomed. Eng.

et al. 2011

Abstract-Our aim was to ascertain whether the ultrasonic measurement of longitudinal corneal apex displacements carried out in a proper headrest is a credible method of ocular pulse detection. To distinguish between longitudinal movements of the eye globe treated as a rigid body and ocular surface expansion caused by the variations of the eye-globe volume, two ultrasound distance sensors were applied to noninvasively measure displacements of cornea and sclera. The same sensors were used to examine the influence of the anterio-posterior movements of a fixed head on the registration of corneal apex pulsation. In both experiments ECG signals were synchronically recorded. Time, spectral and coherence analysis obtained for four healthy subjects showed that the ocular surface expansion due to pulsatile ocular blood flow is the main component of longitudinal corneal displacement. Ocular surface pulsation is always affected by the head movement. However, there exist some unique properties of signals, which help to distinguish between head and eye movements. A rigid headrest and a bite bar are required to stabilize the head during ocular pulse measurement. Ultrasonic technique enables noninvasive and accurate in-vivo measurement of corneal pulsation which could be of interest for indirectly estimating intraocular pressure propagation and pulsatile ocular blood flow component.