Arterial pulse modulates steady-state ocular accommodation

Abstract

Rapid and continuous fluctuations in ocular focus are known to occur when the eye views a stationary target. The advent of high-speed infra-red optometers has established that these microfluctuations of ocular accommodation have two dominant components: low frequency of less than 0.6 Hz and high frequency between 1.0-2.3Hz. Although the retinal image blur associated with microfluctuations has the potential to guide and maintain optimum accommodation levels, there is no consensus with regard to the respective contribution of each of the dominant frequency components. Using a newly-designed measurement and recording system we show that, when viewing a stationary target located at 25cm, individuals exhibit little variation in the frequency of low frequency components but significant variation in high frequency components. Simultaneous measurements of ocular accommodation and systemic arterial pulse demonstrate that the variation in high frequency component is significantly correlated with arterial pulse frequency. Since control experiments indicate that the microfluctuations are derived from activity of the crystalline lens our observations could provide the basis for a non-invasive method of assessing the effects of arterial pulse on ciliary body/choroidal vasculature, the vitreous/lens interface and intraocular pressure. Further, it is feasible that under certain conditions an abnormal increase in the magnitude of arterial pulse may affect the aggregate nature of accommodative microfluctuations to an extent that disrupts the normal control processes maintaining optimum retinal contrast during sustained near vision.

Dynamics of ocular surface topography

“…[17][18][19] In our investigation of the correlation between the microfluctuations in ocular surface wavefront aberrations and pulse and instantaneous heart rates, we found that they were not correlated. We believe that the microfluctuations in the ocular surface wavefront aberrations are primarily the results of the dynamics of the tear film and blinking 20 rather than pulse and instantaneous heart rate.…”

A Dual-Mode Dynamic Model of the Human Accommodation System

“…Thus, there is no overlap of responses by the fast and slow components, which would have caused conflicting commands and potential response instability. It should be pointed out that the previously observed 2 Hz accommodative oscillations under steady viewing conditions (Campbell et al, 1959;Charman and Heron, 1988) has been shown to be an artefact of the arterial pulse on the accommodation measurement device (Winn et al, 1990).…”

Analyzing the Dynamic Wavefront Aberrations in the Human Eye

“…Eye movements and instrument noise contribute only marginally to the measured fluctuations [14]. To date, only the effects of pulse and respiration have been clearly identified in the accommodative signal via coherence analysis [2], [7], [8]. These effects have not been confirmed in the wavefront aberration signal, where the frequency component that could be related to a pulse signal was only occasionally observed [14].…”

“…Traditionally, two main spectral regions are identified for the accommodative fluctuations: the lower frequency region, Hz, and the higher frequency region, Hz. Simple Fourier-transform-based techniques and the coherence analysis have been used to link changes in the accommodation fluctuations with pulse and respiration signals [2], [7], [8].…”