Retinal spectral imaging and spectroscopy are emerging research approaches in Parkinson disease

Retinal hyperspectral imaging (HSI), multispectral/multicolor imaging (MSI/MCI), and diffuse reflectance spectroscopy (DRS) may detect wavelength-dependent optical changes associated with Parkinson’s disease (PD). A scoping review with a prespecified narrow modality scope was conducted in PubMed/MEDLINE, Embase, Scopus, and Web of Science from inception to July 2026. Eligible primary studies used in vivo wavelength-resolved retinal reflectance imaging or spectroscopy in people with clinically diagnosed Parkinson disease or live mammalian models of Parkinson disease or experimental parkinsonism. Human and animal evidence, full articles and conference abstracts, and adjacent optical evidence were synthesized separately. Four in vivo reports met primary eligibility: one small human HSI report, two peer-reviewed animal articles, and one animal conference abstract. The human report included 20 participants with Parkinson disease and 20 controls. Although short-wavelength reflectance differed between groups, discrimination was weak (area under the curve 0.60, 95% confidence interval 0.43–0.78), and the interval included chance-level performance. Animal evidence was heterogeneous: murine HSI showed higher normalized short-wavelength reflectance, whereas targeted spectroscopy in four macaques treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) showed a reduced 480–525-nm spectral slope. The murine multicolor imaging conference abstract reported age-dependent ratio differences but provided limited methodological and validation information. Available studies report retinal spectral differences in PD-related settings, but the evidence is insufficient to assess diagnostic accuracy, biomarker validity, or clinical utility, and no reproducible or disease-specific signature has been established. Instrumental and anatomical harmonization, mechanistic validation, and independent longitudinal clinical cohorts are required. Not applicable.