Does a change in iris diameter indicate heart rate variability?

Abstract

The existence of the retinohypothalamic pathway suggests that light may influence autonomic outflow activity. The objective of this study was to examine the correlation between the estimated iris muscle sympathetic-parasympathetic area (IRIS) ratio and the sympathetic‒parasympathetic ratio (Low Frequency (LF)/High Frequency (HF) ratio). The study population consisted of 200 females and 200 males (mean age, 32.4 ± 7.1 y). The IRIS ratio was determined from digital photographs of the iris in a computer setting. The LF/HF ratio was determined from records of heart rate variability obtained using a Holter implementation. The minimum LF/HF ratio was 1.4 and the maximum 5.6 (mean, 3.0 ± 0.8). The minimum IRIS ratio was 1.4 and the maximum 4.9 (mean, 2.7 ± 0.6). A strong positive correlation was determined between the LF/HF and IRIS ratios in the entire population (r=0.825; p<0.001) and positive correlations were also observed in males and females separately. The intraclass correlation between the LF/HF and IRIS ratios was 0.836. A strong correlation exists between the LF/HF and IRIS ratios.