Abstract
Patients with Alzheimer's disease (AD) and Parkinson's disease (PD) develop a progressive decline of visual function. This condition aggravates overall cognitive and motor abilities, is a risk factor for developing hallucinations, and can have a significant influence on general quality of life. Visual problems are common complaints of patients with PD and AD in the early stages of the disease, but they also occur during normal aging, making it difficult to differentiate between normal and pathological conditions. In this respect, their real incidence has remained largely underestimated, and no rehabilitative approaches have been standardized. With the aim to increase awareness for ocular and visual disorders, we collected the main neurophthalmologic and orthoptic parameters, including optical coherence tomography (OCT), in six patients with a diagnosis of PD, six patients with a diagnosis of early AD, and eight control subjects in an easily assessable outpatient setting. We also evaluated the patient's ability to recognize changes in facial expression. Our study demonstrates that visual problems, including blurred vision, diplopia, reading discomfort, photophobia, and glare, are commonly reported in patients with PD and AD. Moreover, abnormal eye alignment and vergence insufficiency were documented in all patients during examination. Despite the small size of the sample, we demonstrated greater ganglion cell and retinal nerve fibers layer (RNFL) damage and a defect of facial emotion recognition in AD/PD patients with respect to a comparable group of normal elderly persons, with peculiarities depending upon the disease. Ocular defects or visual discomfort could be correctly evaluated in these patients and possibly corrected by means of lens, orthoptic exercises, and visual rehabilitation. Such a practical approach may help to ameliorate motor autonomy, reading ability, and may also reduce the risk of falls, with a positive impact in daily living activities.
Highlights
Neurodegenerative diseases are a heterogeneous group of clinical entities, often presenting with overlapping clinical pictures and characterized by progressive loss of neuronal populations in different brain regions including the visual system
The ganglion cell layer (GCL) of the nasal superior sector was significantly reduced in Parkinson’s disease (PD) patients with respect to Alzheimer’s disease (AD) (p = 0.0201). Both AD and PD patients performed significantly worse than the control group in the task of human facial expressions recognition
An intact vision is crucial in AD to preserve as long as possible visual-dependent cognitive functions, and in PD patients for compensating, through visual guidance, the loss of motor automaticity and postural instability
Summary
Neurodegenerative diseases are a heterogeneous group of clinical entities, often presenting with overlapping clinical pictures and characterized by progressive loss of neuronal populations in different brain regions including the visual system. Its neuropathology begins with the accumulation and propagation of misfolded amyloid β-protein (Aβ) assembly, followed by the hyperphosphorylation of (p)tau proteins, forming neurofibrillary tangles (NFTs) [4] These processes are associated with a cascade of secondary pathologic events, including inflammatory responses, vascular-associated abnormalities, oxidative stress, and mitochondrial dysregulation, leading to massive synaptic and neuronal loss [5,6,7]. The visual system from the peripheral sensory organs to the central integration system may be an early target of neurodegeneration in PD and dementia spectrum disorders. In both AD and PD, the progressive damage of visual function affects overall cognitive and motor abilities, is a risk factor for developing hallucinations, and can have a significant influence on general quality of life. Despite a broad variety of ocular disorders and visual problems being reported in patients with PD and AD, their systematic assessment has remained largely out of focus both in research and clinical practice
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