Eye Tests Predict Parkinson's Progression

Summary: Optical coherence tomography, commonly used in eye exams, can monitor neurodegeneration in Parkinson’s disease patients by measuring the thickness of the retina. This method has revealed that retinal degeneration often precedes cognitive and motor decline, offering a potential early indicator of disease progression.

The study, which tracked changes in Parkinson’s patients from 2015 to 2021, found a significant thinning of the retinal layer linked to the severity of the disease. These findings suggest that eye tests could become a non-invasive tool for predicting the future severity of Parkinson’s symptoms, aiding in more targeted treatment strategies.

Key Facts:

1. Optical coherence tomography was used to measure retinal thickness in Parkinson’s patients, showing that neurodegeneration in the retina precedes cognitive and motor symptoms.
2. The study indicated that a thinner retinal layer at early stages could predict faster cognitive decline and more severe disease progression.
3. This research could lead to the use of routine eye exams as a non-invasive method to monitor and predict the progression of Parkinson’s disease.

Source: University of the Basque Country

Although there are still some aspects pending confirmation for its use in the clinical setting, and its resolution needs to be improved slightly, a study by the UPV/EHU and Biobizkaia has shown that a method routinely used to carry out ophthalmological tests can also be used to monitor the neurodegeneration that occurs in Parkinson’s patients.

In the course of the research, it was found that the neurodegeneration of the retina probably precedes cognitive impairment.

When Parkinson’s or another neurodegenerative disease is diagnosed, patients always ask, “And now what? What will happen? What can be expected from the disease?”

“For neurologists, however, it is not possible to answer these questions precisely, as “the evolution of patients tends to be very varied: some experience no change over the years, while others end up with dementia or in a wheelchair,” explained Ane Murueta-Goyena, researcher in the UPV/EHU’s department of Neurosciences.

Today, identifying Parkinson’s patients at risk of cognitive impairment poses a major challenge, yet this is necessary when it comes to providing more effective clinical treatments and stepping up clinical trials.

In fact, Dr. Ane Murueta-Goyena, in collaboration with Biobizkaia’s research staff, wanted to see “whether the visual system can enable this deterioration to be predicted, in other words, what future the patient can expect within a few years.” The thickness of the retina was used for this purpose.

The retina is a membrane located at the back of the eyeball; it is related to the nervous system and comprises several layers. During the study, a cohort of Parkinson’s patients had the thickness of the innermost layer of their retinas measured using optical coherence tomography.

This type of tomography is a routinely used instrument in ophthalmological tests, as it allows high-resolution, repeatable, and accurate measurements to be made. So the evolution of this retinal layer was analyzed and compared in people with and without Parkinson’s disease over the 2015–2021 period.

The results of the analysis of the images of the retinal layers of Parkinson’s patients were also confirmed in a UK hospital.

The results showed that the retinal layer is noticeably thinner in Parkinson’s patients. It was also observed that “during the initial phases of the disease it is in the retina where the greatest neurodegeneration is detected, and, from a given moment onwards, when the layer is already very thin, a kind of stabilizing of the neurodegeneration process takes place.”

“Retinal thinning and cognitive impairment do not occur simultaneously. The initial changes in the retina are more evident and then, over the years, patients are observed to worsen clinically in both cognitive and motor terms,” explained Murueta-Goya.

“In other words, the slower retinal layer thickness loss is associated with faster cognitive decline; this slowness is linked to greater severity of the disease.”

The researcher has attached great importance to the results. “We have obtained information on the progression of the disease, and the tool we are proposing is non-invasive and available at all hospitals.”

The results need to be validated internationally, and “by slightly improving the resolution of the technology, we will be closer to validating the method for monitoring the neurodegeneration that takes place in Parkinson’s disease.” The researcher also revealed that they are continuing the research on another cohort of patients and that funding is the key.

About this Parkinson’s disease research news

Author: Ane Murueta-GoyenaSource: University of the Basque CountryContact: Ane Murueta-Goyena – University of the Basque CountryImage: The image is credited to Neuroscience News

Original Research: Open access.“Association of retinal neurodegeneration with the progression of cognitive decline in Parkinson’s disease” by Ane Murueta-Goyena et al. npj Parkinson’s Disease

Abstract

Association of retinal neurodegeneration with the progression of cognitive decline in Parkinson’s disease

Retinal thickness may serve as a biomarker in Parkinson’s disease (PD). In this prospective longitudinal study, we aimed to determine if PD patients present accelerated thinning rate in the parafoveal ganglion cell-inner plexiform layer (pfGCIPL) and peripapillary retinal nerve fiber layer (pRNFL) compared to controls.

Additionally, we evaluated the relationship between retinal neurodegeneration and clinical progression in PD. A cohort of 156 PD patients and 72 controls underwent retinal optical coherence tomography, visual, and cognitive assessments between February 2015 and December 2021 in two Spanish tertiary hospitals.

The pfGCIPL thinning rate was twice as high in PD (β [SE] = −0.58 [0.06]) than in controls (β [SE] = −0.29 [0.06], p 

In PD, the progression pattern of pfGCIPL atrophy depended on baseline thickness, with slower thinning rates observed in PD patients with pfGCIPL below 89.8 µm. This result was validated with an external dataset from Moorfields Eye Hospital NHS Foundation Trust (AlzEye study).

Slow pfGCIPL progressors, characterized by older at baseline, longer disease duration, and worse cognitive and disease stage scores, showed a threefold increase in the rate of cognitive decline (β [SE] = −0.45 [0.19] points/year, p = 0.021) compared to faster progressors.

Furthermore, temporal sector pRNFL thinning was accelerated in PD (βtime x group [SE] = −0.67 [0.26] μm/year, p = 0.009), demonstrating a close association with cognitive score changes (β [SE] = 0.11 [0.05], p = 0.052).

This study suggests that a slower pattern of pfGCIPL tissue loss in PD is linked to more rapid cognitive decline, whereas changes in temporal pRNFL could track cognitive deterioration.