BACKGROUND: Purpose of this study was to examine pupil size changes and mobility in normal subjects and in heart failure (HF) patients.METHODS: Sixteen stable patients with New York Heart Association (NYHA) class II or III heart failure and sixteen control subjects were studied. Pupillary reaction to light was recorded and nine parameters from this data were measured, reported and then compared in both groups of subjects.RESULTS: Patients with HF had abnormal pupillary function compared with normal subjects. Pupillary light reflex variables differed significantly between two groups (p < 0.05) except baseline radius (R1), minimum radius (R2) and time for maximum constriction (T3). A significant decrease in maximum constriction velocity (VCmax; p < 0.001) and maximum constriction acceleration (ACmax; p < 0.001) was observed in HF subjects. Furthermore, significantly higher values in percentage recovery-redilatation (%R; p < 0.001), percentage R2/R1 (%R2/R1; p < 0.05), latency (T1; p < 0.05) and time for maximum velocity (T2; p < 0.05) were found in the same group.CONCLUSIONS: Of the parameters studied, R1 and %R are governed mainly by the action of the sympathetic nervous system, through norepinephrine. The rest are governed mainly by parasympathetic nervous system, through acetylcholine. The results of our study demonstrate generalized adrenergic activation and parasympathetic withdrawal, which are present in HF.