What is the clinical evidence from this study?

Study design: Observational. Population: Parkinson's disease (n=71). Intervention: Pupil light reflex measurement vs. Healthy controls. Primary outcome: Peak constriction velocity (short flash) (p=0.03).

August 31, 2023Open Access

Pupil light reflex dynamics in Parkinson’s disease

Q: What does this research mean for the field?

Parkinson's disease patients exhibit significantly slower peak pupil constriction velocity compared to healthy controls, with the defect being more prominent in those with orthostatic hypotension. Novelty: ClaimNovelty.CONFIRMATORY. Consensus alignment: ConsensusAlignment.SUPPORTS_CONSENSUS.

Key Result

Parkinson's disease patients exhibited significantly slower peak pupil constriction velocity compared to healthy controls, with the defect being more prominent in those with orthostatic hypotension.

Study Design

Type

Observational (n=71)

Multicenter

Structured PICO

Are pupil light reflex dynamics altered in patients with Parkinson's disease, and is this associated with orthostatic hypotension?

Population

71 participants (35 healthy controls and 36 early-stage Parkinson's disease patients, Hoehn and Yahr ≤3), recruited in Sweden. PD patients were further divided into those with (n=6) and without (n=30) orthostatic hypotension.

Comparator

Healthy controls

Outcome

Differences in pupil light reflex (PLR) parameters (peak constriction velocity, dilation amplitude and velocity) measured by eye-tracker during long (1,000 ms) and short (100 ms) light stimuli.surrogate

Pupil light reflex dynamics, specifically peak constriction velocity, are impaired in early-stage Parkinson's disease and may be associated with autonomic dysfunction such as orthostatic hypotension.

Main Result

p-value: p=0.03

Limitations

Detailed examination of the autonomic functions was not performed, and the presence of orthostatic hypotension was used as an indicator of dysautonomia
Dilatation and constriction might be influenced by the initial pupil size
All participants with Parkinson's disease were treated with dopaminergic agents and were tested in the ON medication state

Abstract

Introduction: Visual disturbance is common symptom in Parkinson's disease (PD), and defective pupil light reflex (PLR) is an anticipated contributing factor that may be associated to the presence of autonomic dysfunction, which is a common non-motor feature of PD. Studies investigating the intercorrelation between PLR and dysautonomia in PD are limited. Methods: The aim of this study was to investigate differences of PLR parameters, measured by eye-tracker, between patients with PD, with and without signs of dysautonomia, and healthy controls (HC). In total, 43 HC and 50 patients with PD were recruited and PLR parameters were measured with Tobii Pro Spectrum, during a long (1,000 ms) and a short (100 ms) light stimulus. Presence of orthostatic hypotension (OH) was used as proxy marker of dysautonomia. Linear mixed-effects model and non-parametric comparative statistics were applied to investigate differences among groups. Results: Peak constriction velocity was slower in PD compared with HC, after adjustment for age and sex in the mixed model, and the difference was greater in the subgroup of PD with OH (unadjusted). Dilation amplitude and velocity were also gradually slower in HC vs. PD without OH vs. PD with OH (unadjusted for confounders). In the mixed model, age was significant predictor of dilation response. Discussion: Our results support previous observations on defective PLR in PD, evaluated with eye-tracker, and show a possible association with autonomic dysfunction. Further studies with more patients and rigorous evaluation of autonomic dysfunction are needed to validate these findings.

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