Intraocular pressure variability in the anesthetized rat: a spectral analysis

Intraocular pressure (IOP) is a measure of the balance between the inflow and outflow of the aqueous humor, being in close relationship with the venous ocular blood flow. But the influence of the autonomic nervous system upon this variable is not well understood. One of the most frequently used mathematical tools for the evaluation of the autonomic nervous system in the frequency domain is the fast Fourier algorithm (FFT) applied to the analysis of heart rate (HR) and arterial blood pressure (BP). For these variables, a power spectrum has been built showing the major bands: very low frequency, lower frequency, and higher frequency (HF). The range of these bands depends on the animal species. In this study, the authors used FFT to analyze the variability of IOP in anesthetized rats.

BP and electrocardiogram were acquired at 2 KHz in all animals before and following muscle blockade and artificial ventilation at the same frequency as the spontaneous ventilation. Also, in this last condition, IOP was recorded before and after the application of atropine in the eye.

Results show three bands in the IOP spectrum, a similar profile to those observed in the HR and BP spectra, with HF band modified after atropine application

The discussion calls attention to the influence of the autonomic nervous system on IOP and suggests the possibility of clinical application of this methodology on diagnosis and therapeutic efficacy.