Parkinson’s disease is primarily known for its motor symptoms, but growing evidence suggests early neurodegenerative changes also occur in the retina, with optical coherence tomography emerging as a promising tool for detecting these retinal alterations.
In their study published in Acta Neuropathologica Communications, Ane Murueta-Goyena, PhD, and colleagues provided an in-depth analysis of retinal changes in early-stage PD, suggesting that these alterations may serve as valuable biomarkers for disease progression.
The prospective, 1-year longitudinal multicenter study involved 53 early-stage PD patients (disease duration ≤ 5 years) and 52 healthy controls. Participants underwent spectral-domain OCT imaging alongside visual function and cognitive assessments. The researchers aimed to identify specific patterns of retinal layer changes and their potential associations with disease progression.
The study found increased ganglion cell-inner plexiform layer (GCIPL) thickness in the central macular region of PD patients compared to controls. The central 1-mm disc region exhibited a mean increase of 3.8 μm, while the adjacent parafoveal 1- to 2-mm ring showed a 4.5 μm increase.
Over the 1-year follow-up, PD patients exhibited significantly faster GCIPL thinning in the parafoveal 2- to 3-mm ring, at a rate of -0.61 ± 0.29 μm/year compared to controls. A similar trend was observed in the 3- to 4-mm ring, albeit at a near-significant level.
“We found that greater increases in central GCIPL thickness were associated with more pronounced parafoveal GCIPL atrophy over the follow-up period, further emphasizing the importance of examining central retinal changes as early indicators of PD progression,” the authors noted.
The study also found that greater central GCIPL thickness correlated with poorer contrast sensitivity and performance on the Farnsworth D-15 color vision test. However, there were no significant associations were found between GCIPL thickening and motor or cognitive symptoms at baseline.
The study provided evidence of retinal changes in early-stage PD that occur prior to significant clinical progression. The paradoxical increase in central GCIPL thickness preceding its later thinning suggests that early neuroinflammatory or vascular changes may be contributing factors, the authors noted. These findings reinforce the potential of OCT as a noninvasive biomarker for tracking PD progression.
“Our results indicate that early retinal alterations in PD patients, particularly in the macular region, exhibit complex and variable dynamics,” Dr Murueta-Goyena wrote. “The complex interplay between increased central GCIPL thickness and subsequent thinning of inner retinal layers in the parafoveal and perifoveal regions shows differential progression patterns within PD subjects, whereas pRNFL thinning follows a more consistent trajectory across the cohort.”
The exact mechanisms underlying these retinal alterations remain unclear, and longer-term follow-ups and studies integrating advanced imaging techniques with molecular biomarkers can aid in validating OCT-based markers for PD.
The authors declared no competing interests with the study.