Structural and functional changes in the retina in Parkinson’s disease

Abstract

Parkinson’s disease is caused by degeneration of dopaminergic neurons, originating in thesubstantia nigra pars compactaand characterised by bradykinesia, rest tremor and rigidity. In addition, visual disorders and retinal abnormalities are often present and can be identified by decreased visual acuity, abnormal spatial contrast sensitivity or even difficulty in complex visual task completion. Because of their early onset in patients with de novo Parkinson’s disease, the anatomical retinal changes and electrophysiological modification could be valuable markers even at early stages of the disease. However, due to the concomitant occurrence of normal ageing, the relevance and specificity of these predictive values can be difficult to interpret. This review examines retinal dysfunction arising in Parkinson’s disease. We highlight the electrophysiological delays and decreased amplitude in the electroretinography recorded in patients and animal models. We relate this to coexisting anatomical changes such as retinal nerve fibre layer and macular thinning, measured using optical coherence tomography, and show that functional measures are more consistent overall than optical coherence-measured structural changes. We review the underlying chemical changes seen with loss of retinal dopaminergic neurons and the effect of levodopa treatment on the retina in Parkinson’s disease. Finally, we consider whether retinal abnormalities in Parkinson’s disease could have a role as potential markers of poorer outcomes and help stratify patients at early stages of the disease. We emphasise that retinal measures can be valuable, accessible and cost-effective methods in the early evaluation of Parkinson’s disease pathogenesis with potential for patient stratification.

Neurodegeneration with Brain Iron Accumulation Disorders and Retinal Neurovascular Structure

“…This finding was consistent with more frequently detected abnormal results of ERG in these patients compared with other NBIA subtypes. Reasons other than structural distortion have been postulated for abnormal ERG results by Alves et al, 52 like dopaminergic defects in PD.…”

Advancing systemic disease diagnosis through ophthalmic image‐based artificial intelligence

“…This neural continuum enables the ophthalmologist to indirectly assess neurologic health. Pathological thinning of the retinal nerve fiber layer could signify axonal loss, an early sign of neurodegenerative diseases like Alzheimer's 31,32 and Parkinson's 33,34 . Technologies such as OCT, minute changes in retinal thickness can be measured, offering potential early markers for neural pathology 35,36 …”

“…There are various retinal imaging techniques available, including retinal neurovascular structure imaging and retinal electrical activity functional imaging, that have been recognized to be affected by systemic diseases. 34,41 However, for AI analysis, the data that is more easily accessible in large quantities is more conducive to training the model and applying it in hospitals or communities. Therefore, the focus of research has been on using imaging techniques such as CFPs, which can provide large volumes of data for AI analysis.…”

Deep Learning, the Retina, and Parkinson Disease

“…The purpose of our study 1 was to determine whether deep-learning methods can provide information that the retina can reflect cognitive functional changes in the brain. Although there have been previously published studies about retinal changes in PD, 5 the associations were inconsistent and the studies were based on less accessible and more expensive examinations, such as optical coherence tomography. Our study has shown that by using deep-learning methods on fundus photography, the retina can provide objective information regarding neurofunctional changes in patients with PD.…”