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Monika Ewa Danielewska, D. Robert Iskander; Age and ocular dicrotism - spectral representations of corneal indentation pulse and cardiovascular signals in healthy and glaucomatous eyes. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3369.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the spectral characteristics of the ocular dicrotic pulse (ODP), recently observed in healthy elderly subjects, glaucomatous and glaucoma suspects eyes with age.
Retrospective signals of corneal indentation pulse (CIP) and heart activity (blood pulse (BPL) and ECG) acquired in a study of ocular dicrotism were considered [Danielewska et al., PloS One, 2014]. The study involved 261 subjects classified into 4 groups: primary open angle glaucoma (70 patients; Mean±SD=60.0±6 y.o.), primary angle-closure glaucoma (61 patients; 65.0±7.6 y.o.), glaucoma suspects with glaucomatous optic disc appearance (60 patients; 66.6±9.7 y.o.) and the control group (70 healthy subjects (61.2±5.3y.o.)). Subjects were divided into two age subgroups around the median age of 63 and two CIP groups (with and without ODP). Spectral estimation of CIP, BPL and ECG signals was performed in a custom program written in Matlab. Parameters related to amplitudes of and the energies surrounding the first 6 harmonics were evaluated in spectral and coherence domains. Statistical analysis included standard descriptive statistics and hypothesis testing using the general linear model (2-way ANOVA). The significance level was set to α=0.05.
In the spectral domain, statistically significant changes were recorded only for age for the second harmonic of CIP for subjects without ODP. In the coherence domain (where CIP signals were compared to BPL and ECG signals), statistically significant changes were found for age for the first harmonic (CIP&BPL) and for the subject group for the third and fifth harmonic (CIP&ECG) for subjects without ODP. For subjects with ODP statistically significant changes were found for the subject group for the sixth harmonic (CIP&BPL; CIP&ECG). Additionally, statistically significant changes were observed in the coherence domain for the groups with and without ODP for the odd harmonics (CIP&BPL).
Spectral analysis does not provide unambiguous representation of CIP signals and cannot be used as tool for discriminating subjects without ODP from those with ODP without taking into consideration signals of heart activity. Also, spectral analysis can be used to separate the younger subjects from the older one but this discrimination is evident only for subjects without ODP, indicating that the spectra of the ODP signals are less variable.
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