Autonomic correlates of ocular accommodation and cardiovascular function.
Level 4 - case-series / case-control
Cross-sectional physiological observational study in humans
PubMed 19523088 · doi:10.1111/j.1475-1313.2009.00635.x
What was done
Sixty healthy young adults (29 males, 31 females; mean age 20.3 ± 2.9 years; spherical equivalent -7.12 to +1.82 D) underwent continuous objective measurement of ocular accommodation using an open-view infrared autorefractor across open- and closed-loop accommodative demands (five 20-second recordings). Concurrently, heart rate was monitored for 5 minutes using a finger-mounted piezoelectric pulse transducer. Fast Fourier Transform spectral analysis was used to assess frequency-domain autonomic components (sympathetic and parasympathetic power), alongside time-domain heart period metrics.
What was found
Increasing closed-loop accommodative demand resulted in a concurrent heart rate elevation of approximately 2 beats/min for a 4.0 D increase in demand. This shift was accompanied by a significant reduction in both absolute (p < 0.05) and normalized (p < 0.001) systemic parasympathetic power. These autonomic changes did not significantly differ across refractive error groups.
Why it matters
This study demonstrates physiological covariation between ocular accommodation and the cardiovascular system, showing that near-visual tasks modulate cardiovascular function primarily via parasympathetic nervous system withdrawal.
Limits
The sample was restricted to young adults (aged 18–33 years), limiting generalizability to presbyopic or older populations. Autonomic assessment relied on a finger pulse transducer rather than gold-standard multi-lead electrocardiography, and the acute physiological effect size (a 2 bpm change over short visual tasks) may have limited long-term or clinical significance.
Cited by
- context Viewing a broad visual horizon widens the visual field, which reduces sympathetic nervous system activation and promotes parasympathetic nervous system activity.