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. 2022 Jun 13;35(4):332-340.
doi: 10.4103/1319-4534.347306. eCollection 2021 Oct-Dec.

Pupil light reflex in Parkinson's disease patients with and without freezing of gait symptoms

Mosaad Alhassan  1 , Jeffery K Hovis  2 , Quincy J Almeida  3
Affiliations

Pupil light reflex in Parkinson's disease patients with and without freezing of gait symptoms

Mosaad Alhassan et al. Saudi J Ophthalmol. .

Abstract

Purpose: Freezing of gait (FOG) is considered as a motor disorder that affects some Parkinson's disease (PD) patients; however, sensory systems may also be involved in FOG. The pupil light reflex (PLR) is a reliable measure of the autonomic nervous system. Different dilation and constriction pupil parameters may be used to investigate the integrity of the autonomic nervous system in PD patients with and without FOG symptoms. This study aimed to look at the integrity of autonomic nervous system and to investigate the nonmotor functions mediated by the cholinergic system in Parkinson's patients with and without FOG symptoms.

Methods: Constriction and dilation pupil light reflexes were measured by using a handheld pupillometer. Twenty-two patients with FOG symptoms, 25 patients without FOG symptoms, and 25 aged-matched healthy controls participated in this study.

Results: The results showed that most of the constriction parameters and dilation latency of both patient groups differed significantly from healthy controls. FOG patients showed larger pupil size under light condition and larger deficits in constriction latency than nonFOG patients. Both the groups of PD patients had longer dilation latencies than healthy controls.

Conclusion: This study suggests that the cholinergic autonomic nervous system is affected in PD patients more than the adrenergic system. FOG patients had larger impairments in nondopaminergic mediated functions such as pupil light reflexes, which suggests that FOG patients have greater impairment in functions that involve cholinergic neurotransmitters.

Keywords: Autonomic nervous system; Parkinson’s disease; freezing of gait; nonmotor; pupil light reflex; sensory.

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Conflict of interest statement

There are no conflicts of interest.

Figures

Figure 1
Figure 1
Pupil size response to light stimulus as a function of time in 3 representative participants from each group. The two yellow vertical lines show where the stimulus started and ended, the black vertical line shows the constriction latency, the blue vertical line shows T75%. (a) Freezing of gait Parkinson’s disease patient, (b) non-Freezing of gait Parkinson’s disease patient, (c) Healthy control subject
Figure 2
Figure 2
Pupil size response to light stimulus as a function of time in three different participants representing the three subject groups. The two yellow lines show where the stimulus started and ended, the black vertical line shows the dilation latency. (a) Freezing of gait Parkinson’s disease patient, (b) non-Freezing of gait Parkinson’s disease patient, (c) Healthy control subjects
Figure 3
Figure 3
Scatter plots of pupil maximum constriction velocity as a function amplitude of pupil constriction for the subject groups
See this image and copyright information in PMC

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