The pupil light reflex is a sensitive tool to assess parasympathetic dysfunction, particularly using maximum constriction velocity and relative constriction amplitude, though evidence linking it to hearing impairment is currently limited.
Systematic Review (n=38)
Is the pupil light reflex a sensitive method to evaluate parasympathetic dysfunction, and is there a connection to hearing impairment?
The pupil light reflex is a sensitive tool to assess parasympathetic dysfunction, but its connection to hearing impairment requires further research.
CONTEXT: Although the pupil light reflex has been widely used as a clinical diagnostic tool for autonomic nervous system dysfunction, there is no systematic review available to summarize the evidence that the pupil light reflex is a sensitive method to detect parasympathetic dysfunction. Meanwhile, the relationship between parasympathetic functioning and hearing impairment is relatively unknown. OBJECTIVES: To 1) review the evidence for the pupil light reflex being a sensitive method to evaluate parasympathetic dysfunction, 2) review the evidence relating hearing impairment and parasympathetic activity and 3) seek evidence of possible connections between hearing impairment and the pupil light reflex. METHODS: Literature searches were performed in five electronic databases. All selected articles were categorized into three sections: pupil light reflex and parasympathetic dysfunction, hearing impairment and parasympathetic activity, pupil light reflex and hearing impairment. RESULTS: Thirty-eight articles were included in this review. Among them, 36 articles addressed the pupil light reflex and parasympathetic dysfunction. We summarized the information in these data according to different types of parasympathetic-related diseases. Most of the studies showed a difference on at least one pupil light reflex parameter between patients and healthy controls. Two articles discussed the relationship between hearing impairment and parasympathetic activity. Both studies reported a reduced parasympathetic activity in the hearing impaired groups. The searches identified no results for pupil light reflex and hearing impairment. DISCUSSION AND CONCLUSIONS: As the first systematic review of the evidence, our findings suggest that the pupil light reflex is a sensitive tool to assess the presence of parasympathetic dysfunction. Maximum constriction velocity and relative constriction amplitude appear to be the most sensitive parameters. There are only two studies investigating the relationship between parasympathetic activity and hearing impairment, hence further research is needed. The pupil light reflex could be a candidate measurement tool to achieve this goal.
Wang et al. (Mon,) conducted a systematic review in Parasympathetic Nervous System Dysfunction and Hearing Impairment (n=38). Pupil light reflex (PLR) vs. Healthy controls was evaluated on Sensitivity of PLR parameters to detect parasympathetic dysfunction. The pupil light reflex is a sensitive tool to assess parasympathetic dysfunction, particularly using maximum constriction velocity and relative constriction amplitude, though evidence linking it to hearing impairment is currently limited.