More than half of all Alzheimer’s patients lose the ability to interpret what they see—not because their eyes are failing, but because the brain regions that process vision are damaged by dementia. This “cortical visual impairment” is routinely missed by eye doctors, who mistake it for ordinary eyesight problems. Patients spend years getting new glasses or even cataract surgery before anyone realises the issue is in the brain, not the eye. The project takes a lab-based test called the Graded Incomplete Letters Test (GILT), already used in UK Biobank, and turns it into a simple iPad or smartphone app. Researchers will validate it in eye clinics in London, Lyon, and Israel, and work with optometrists to make sure it fits into routine practice. If successful, the app could let opticians and GPs distinguish dementia-related vision loss from glaucoma or cataracts in a single appointment. That would cut years of misdiagnosis, spare patients unnecessary surgery, and get them into specialist dementia care sooner. The work is applied, not fundamental science—it aims to put a diagnostic tool directly into the hands of the clinicians who currently miss these patients.
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Context Cortical visual impairment caused by dementia (‘brainsight’, rather than eyesight loss) is associated with devastating consequences for independence, even more so than memory impairment. In Alzheimer’s disease (AD), the most common form of dementia, such visual impairment has been documented in more than half of patients, and can be the first sign of AD in posterior cortical atrophy (PCA; the most common atypical form of AD, which is visual-, not memory-led). Challenges the project addresses Dementia-related visual impairments fall between medical specialties particularly given patients often present initially to eyecare professionals. Correspondingly, such impairments are frequently overlooked or misdiagnosed, delaying diagnosis and treatment for years. Diagnostic challenges faced by people with dementia and their carers include unsuccessfully changing glasses or having surgery before realising issues do not relate to eyesight, but cortical visual loss. Challenges posed to detection of dementia-related visual impairment range from difficult-to-access specialist neurologic services and the current lack of tests suitable to detect higher-order cortical visual impairments in the eye services where patients typically first present. There is a need to distinguish higher-order cortical vision loss from eyesight-related loss in aging populations (e.g. differentiating PCA from glaucoma). Aims and Objectives We have developed a novel test to detect and distinguish cortical visual from ocular deficits (Graded Incomplete Letters Test; GILT) implemented within UK BioBank (UKB). GILT is currently lab-based, requires specialist software and its use has so far been restricted to research cohorts (UKB and UCL). Advancing Detection of dementia-related Cortical Visual Impairment (AD-CVI) will produce GILT versions suitable across research and clinical settings (WP1). We will validate GILT in UK (Moorfields Eye Hospital) and international eye clinics (Bergman Eye Clinics; Hospices Civil de Lyon) (WP2). We will evaluate GILT useability and feasibility through engaging eye professionals and inform refinements maximising GILT clinical utility. Key objectives Develop GILT versions available via iOS and Android devices Conduct GILT version testing and calibration for consistency across devices Validate the GILT in ophthalmic clinical and research settings Conduct user testing with professionals working across ophthalmic services Develop a UKCA Class 1 Licensed GILT available via iPad with prototyped web-based version Applications and benefits This work will benefit: Patients through accurate diagnosis enabling early treatment, symptom understanding and putting in place support tailored to visual loss. Staff through improved sight assessment for people with dementia. Services through reducing diagnostic delays and misdiagnoses: in particular, avoiding repeated visits with eye professionals, unsuccessful surgery and psychiatric referrals. Core team: Project lead: Dr Keir Yong (UCL) Project co-lead (international): Prof Aaron Seitz (Northeastern University), Prof Caroline Froment Tilikete (Hospices Civil de Lyon) Specialists: Prof John Greenwood (UCL), Dr Hari Jayaram & Dr Ahmed Toosy (Moorfields Eye Hospital), Dr Peter Jones (Irida Health Ltd) Partner organisations: College of Optometrists, Glaucoma UK, UK & Ireland Society of Cataract Surgeons
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