JMIR Publications

ABSTRACT

Background:

Visual impairment is a common co-morbidity experienced by people living with dementia (PWD). A recent study found 62% of PWD had a remediable form of visual impairment - quality of vision has been linked to cognitive decline in PWD, thus addressing sources of visual difficulties can have significant impact upon quality of life for PWD and their caregivers. Depth perception problems are stated as being common in dementia, and also contribute to falls, visuomotor task difficulties and poorer psychosocial wellbeing. Yet depth perception/binocular vision is rarely assessed in such studies. Further, sleep fragmentation is a common experience for PWD, and binocular cooperation for depth perception can be affected by fatigue. The interactions between visual function, binocular function, sleep quality and rate of cognitive decline in PWD are yet to be formally evaluated. Pupil responses under cognitive load also have potential as a risk marker for cognitive decline in PWD, and can be combined with the above measures for a comprehensive evaluation of clinical visual changes in PWD and their relationship to changes in cognitive status, sleep quality, and cortical structure/function.

Objective:

To characterise the nature of clinical visual changes and altered task-evoked pupil responses that may occur in PWD, and whether these relate to changes in cognitive status (standardised Mini Mental State Examination Score), sleep quality and cortical structure/function.

Methods:

The proposed exploratory observational study will measure the following in up to 210 people with recently-diagnosed dementia (within last 24 months) on 3 occasions, 4 months apart (± 2 weeks): • Visual function (visual acuity, contrast sensitivity) • Binocular function (motor fusion, stereopsis) • Task-evoked pupil responses (minimum/maximum pupil size, time to maximum dilation, dilation velocity) • Cognitive status (standardised Mini Mental State Examination) • Sleep quality (Pittsburgh Sleep Quality Index) A subset (n = 30) with Alzheimer's disease will receive structural/functional MRI scanning on first and third visit, and complete a 10 day consensus sleep diary to monitor sleep quality, verified by data from an activity watch worn during the same period. Analysis will explore: 1) Prevalence of abnormal binocular function and task-evoked responses in PWD 2) Relationships between changes (over an 8 month period) in visual function, binocular function, pupil function, cognitive status, sleep quality and, for people with Alzheimer's disease, volumetric parameters/BOLD activation in cortical visual areas.

Results:

Current status: This research was funded in February 2018 and received National Health Service Research Ethics Committee approval in September 2018. The data collection period is 1st October 2018 to 30th October 2019.

Conclusions:

Findings will show how often people with dementia experience binocular vision problems. If frequent, diagnosing/treating them could improve quality of life through reducing risk of falls and fine visuomotor task impairment,and relieving psychosocial anxiety. This research will also show whether changes in depth perception, pupil responses and quality of vision relate to changes in memory or sleep quality, and brain structure/function. If related, these quick and non-invasive eye-tests help monitor dementia. This would help justify whether binocular vision and pupil response testing should be included in dementia-friendly eye-testing guidelines.