The clinical approach to the identification of higher-order visual dysfunction in neurodegenerative disease

This review is intended to assist the reader in gaining the knowledge and skills necessary for the recognition and assessment of higher-order visual dysfunction due to neurodegenerative diseases including Alzheimer's disease, dementia with Lewy bodies, Parkinson's dementia, corticobasal degeneration, Creutzfeldt-Jakob disease, and the posterior cortical atrophy syndrome. Clinical problem-solving and pattern recognition must be developed and practiced to accurately diagnosis disturbances of higher-order visual function, and knowledge of higher-order visual brain regions and their visual syndromes forms the foundation for deciphering symptoms presented by patients and/or their care partners. Tests of higher-order visual dysfunction must be assembled by the clinician and assessment can take time and effort. The use of screening tests, follow-up visits, and formal neuropsychological referrals are critical components for accurate diagnosis and these principles are reviewed here.

A recent survey of neuro-ophthalmologists revealed that over half of the respondents report that 5-10% of their new patient referrals carry a diagnosis of neurodegenerative disease and many patients were referred for visual symptoms of unknown cause. Despite over a century of discovery related to higher-order visual functions of the human brain, translation of discovery to the clinical assessment of patients has been slow or absent. As with the approach to translational medicine in general, to see meaningful progress, an interdisciplinary approach is indispensable. The first step involves the application of discoveries from the field visual neuroscience by clinicians from the fields of ophthalmology, neurology, and neuropsychology, and from the disciplines of neuro-ophthalmology and behavioral neurology. The unmet need for recognition, assessment, and management of higher-order visual dysfunction in neurodegeneration is evident and clinicians can contribute to closing the gap by using the approach and the tools outlined in the review.