In a recent IOVS study, researchers from the First Affiliated Hospital of Harbin Medical University, China, have demonstrated that corneal nerve imaging via in vivo confocal microscopy (IVCM) can differentiate motor subtypes of Parkinson’s disease (PD) – a development with significant implications for early diagnosis and prognosis.
The study involved 63 PD patients and 31 age- and gender-matched controls. PD participants were classified into tremor-dominant (TD), postural instability and gait disturbance (PIGD), and mixed subtypes. Using IVCM, the researchers analyzed central and inferior whorl-like corneal nerve parameters – areas that are rich in small sensory fibers and notably vulnerable in neurodegenerative diseases.
Compared to the healthy controls, PD patients showed significant reductions in several corneal nerve metrics, including corneal nerve fiber length (CNFL), area (CNFA), width (CNFW), and fractal dimension (CNFrD), along with inferior whorl (IWL)-specific indicators. Notably, PIGD patients displayed the most pronounced deficits.
The study also found that reductions in CNFA and CNFrD correlated with higher MDS Unified Parkinson's Disease Rating Scale (MDS-UPDRS) III scores and lower Montreal Cognitive Assessment (MoCA) scores, linking corneal nerve changes to both motor and cognitive dysfunction. PD patients in the study also exhibited decreased corneal sensitivity, tear production (Schirmer I), and tear film stability (TBUT), reinforcing the ophthalmic impact of PD.
The research indicates that IVCM could become a valuable tool in the neurologist’s and ophthalmologist’s arsenal, providing early, non-invasive insights into PD subtype, severity, and progression. While longitudinal studies are needed to confirm temporal changes and treatment effects, this method holds promise for both clinical stratification and research monitoring of Parkinsonian neuropathology.
