Evaluation of autonomic involvement in Parkinson's disease using pupillometry

The pupillary light reflex (PLR) indicates the function of the autonomic nervous system, which causes the pupil to constrict and dilate. Evaluation of the PLR determines the parasympathetic and sympathetic balance. We aimed to demonstrate autonomic changes by pupillometry in Parkinson'd disease (PD) and to investigate the relationship between the changes and motor stage and levodopa equivalent dose (LEDD).

Static pupillometry measurement was performed at scotopic, mesopic and photopic settings. Dynamic pupillometry measurement was performed at 500 lux illumination and pupil diameter was recorded. Static and dynamic pupillometry parameters of Parkinson's disease patients and healthy control group of similar age and gender were compared. The relationship between Unified Parkinson's Disease Rating Scale (UPDRS)-motor, modified Hoehn and Yahr (mHYE) and levodopa equivalent daily dose (LEDD) and pupillometry parameters were analysed.

In static pupillometry, mesopic pupil diameter was significantly lower in PD patients (P = 0.04). In dynamic pupillometry, pupil diameter was lower and mean pupil dilation rate was lower in the PD group at 18 seconds. There was a significant negative correlation between mean pupil dilatation velocity and mHYE, UPDRS-motor and LEDD. The mean pupil dilatation velocity was statistically significantly lower in patients not receiving dopaminergic treatment.

Changes in pupillometry values in PD have emphasized that the autonomic nervous system is affected and the parasympathetic nervous system was found to be correlated with the motor involvement of the disease.