Abstract
Background: Convergence insufficiency (CI) in parkinsonian conditions causes disabling visual symptoms during near tasks and usually manifests as double vision. Since double vision is more common in patients who report cognitive symptoms, we sought to determine if symptomatic CI, as opposed to asymptomatic CI, could serve as a marker of cognitive impairment in parkinsonian disorders.Methods: Twenty-four participants with parkinsonian disorders (18 Parkinson's disease, 5 progressive supranuclear palsy, 1 multiple system atrophy) and objective findings of convergence insufficiency on neuro-ophthalmologic examination were included. Subjective visual symptoms and cognitive complaints were recorded, and the Self-Administered Gerocognitive Examination was used as a global cognitive screening measure.Results: 54.1% of parkinsonian participants had cognitive impairment, but there were no significant differences in the degree of convergence insufficiency, measured by near point of convergence (NPC), or cognitive outcomes between those with symptomatic CI, and asymptomatic CI. However, NPC was greater for those with cognitive impairment (x = 18.4 cm), compared to those who were cognitively intact (x = 12.5 cm, p = 0.003).Conclusions: Cognitive impairment commonly co-occurs in parkinsonian disorders with convergence insufficiency and is associated with significantly greater NPC distances. Clinicians should have a high index of suspicion for cognitive impairment in patients with objective findings of convergence insufficiency, whether symptomatic or not. Further investigation of convergence insufficiency in relationship to cognitive impairment in parkinsonian disorders is warranted, as there may be a shared mechanism of dysfunction.
Highlights
Disjunctive, binocular eye movements performed to maintain single vision during near target viewing is referred to as convergence
Convergence insufficiency has the potential to result from impaired subcortical and/or cortical function since, beyond the midbrain, it has been postulated that reflexive convergence that is stimulus bound is controlled by posterior parietal regions while volitional convergence is controlled by frontal cortical regions [3]
Twenty-four patients were identified with parkinsonian disorders, convergence insufficiency, and visual complaints, who had undergone complete neuro-ophthalmologic evaluation and had Self-Administered Gerocognitive Examination (SAGE) data available
Summary
Disjunctive, binocular eye movements performed to maintain single vision during near target viewing is referred to as convergence. Parkinsonian disorders frequently result in impaired convergence, which is a cause of disabling visual dysfunction, and decreased quality of life [1]. Convergence insufficiency (CI) presents with symptoms of double or blurred vision while reading or performing near tasks. One group found cognitive complaints to be more common in patients with Parkinson’s disease (PD) who reported diplopia [2], but the relationship between cognitive impairment and symptomatic convergence insufficiency in parkinsonian disorders has not been previously investigated. Convergence insufficiency (CI) in parkinsonian conditions causes disabling visual symptoms during near tasks and usually manifests as double vision. Since double vision is more common in patients who report cognitive symptoms, we sought to determine if symptomatic CI, as opposed to asymptomatic CI, could serve as a marker of cognitive impairment in parkinsonian disorders
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