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Autonomic correlates of ocular accommodation and cardiovascular function
Article first published online: 3 JUN 2009
© 2009 The Authors. Journal compilation © 2009 The College of Optometrists
Ophthalmic and Physiological Optics
Volume 29, Issue 4, pages 427–435, July 2009
How to Cite
Davies, L. N., Wolffsohn, J. S. and Gilmartin, B. (2009), Autonomic correlates of ocular accommodation and cardiovascular function. Ophthalmic and Physiological Optics, 29: 427–435. doi: 10.1111/j.1475-1313.2009.00635.x
- Issue published online: 3 JUN 2009
- Article first published online: 3 JUN 2009
- Received: 12 August 2008 Revised form: 2 January 2009 Accepted: 3 January 2009
- autonomic nervous system;
- heart rate variability;
- refractive error
Purpose: To evaluate the hypothesis that objective measures of open- and closed-loop ocular accommodation are related to systemic cardiovascular function, and ipso facto autonomic nervous system activity.
Methods: Sixty subjects (29 male; 31 female) varying in age from 18 to 33 years (average: 20.3 ± 2.9 years) with a range of refractive errors [mean spherical equivalent (MSE): −7.12 to +1.82 D] participated in the study. Five 20-s continuous objective recordings of the accommodative response, measured with an open-view IR autorefractor (Shin-Nippon SRW-5000), were obtained for a variety of open- and closed-loop accommodative demands while simultaneous continuous measurement of heart rate was recorded with a finger-mounted piezo-electric pulse transducer for 5 min. Fast Fourier Transformation of cardiovascular function allowed the absolute and relative power of the autonomic components to be assessed in the frequency-domain, whereas heart period gave an indication of the time-domain response.
Results: Increasing closed-loop accommodative demand led to a concurrent increase in heart rate of approximately 2 beats/min for a 4.0 D increase in accommodative demand. The increase was attributable to a reduction in the absolute (p < 0.05) and normalised (p < 0.001) input of the systemic parasympathetic nervous system, and was unaffected by refractive group. The interaction with refractive group failed to reach significance.
Conclusions: For sustained accommodation effort, the data demonstrate covariation between the oculomotor and cardiovascular systems which implies that a near visual task can significantly influence cardiovascular behaviour. Accommodative effort alone, however, is not a sufficient stimulus to induce autonomic differences between refractive groups. The data suggest that both the oculomotor and cardiovascular systems are predominantly attributable to changes in the systemic parasympathetic nervous system.