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Abstract

PURPOSE: This study aimed to evaluate the total macular thickness as well as the thickness of the inner and outer retinal layers in patients with Parkinson's disease. It also aimed to verify the correlation of these parameters with motor symptoms and cognitive function.
METHODS: A total of 46 eyes of 23 patients with Parkinson's disease and 40 eyes of 20 healthy controls were included in the study. The patients' cognitive, functional, and nonmotor symptoms were evaluated using the Katz Index of Independence and Pfeffer's Activities of Daily Living, Mini-Mental State Examination, Frontal Assessment Battery, Schwab and England Staging Scales, and Movement Disorders Society Nonmotor Symptoms Scale. The macular thickness measurements obtained via total, inner, and outer optical coherence tomography were recorded. Furthermore, the correlation of the parameters of optical coherence tomography with cognitive, functional, and nonmotor symptoms was assessed.
RESULTS: The scores of the Katz Index of Independence and Pfeffer's Activities of Daily Living as well as the Movement Disorders Society Nonmotor Symptoms Scale were significantly lower in patients with Parkinson's disease than in healthy controls. Moreover, the former had greater total macular thickness. The temporal and inferior outer sectors were significantly greater for the ganglion cell complex thickness in patients. A significant correlation was observed between the total macular thickness and the Movement Disorder Society-Unified Parkinson's Disease Rating Scale, Parte III (MDS-UPDRS-III) values. Contrarily, there was a negative correlation between the outer macular thickness and the MDS-UPDRS-III values. Meanwhile, the total macular thickness and ganglion cell complex thickness were significantly correlated with the scores of the Mini-Mental State Examination, Schwab and England Staging Scale, Frontal Assessment Battery, and Katz Index of Independence and Pfeffer's Activities of Daily Living. In addition, the Schwab and England scale was correlated with the outer macular thickness.
CONCLUSION: The total and inner macular thicknesses at the temporal and inferior outer sectors were greater in patients with Parkinson's disease than in the control group. These findings indicate that macular thickness may be greater in those with Parkinson's disease, particularly when associated with mild motor symptoms. In addition, the parameters of the total, inner, and outer optical coherence tomography were significantly associated with motor and nonmotor symptoms as well as cognitive function impairment.

Keywords: Parkinson's disease; Tomography, optical coherence; Neurodegenerative diseases; Cognitive dysfunction; Cognition; Motor perception; Visual acuity; Retina

Abstract

Corneal blindness affects more than 12 million individuals worldwide; however, the availability of human donor corneas meets only a small fraction of the demand. Porcine corneal xenotransplantation represents a promising alternative because of the cornea's immune privilege and the anatomical similarities between human and porcine corneas. However, the galactose-α1,3-galactose antigen expressed on porcine cells induces hyperacute rejection through the activation of human anti-Gal antibodies, complement pathways, and innate immune cell infiltration. This review summarizes the mechanisms underlying corneal immune privilege and contrasts them with galactose-α1,3-galactose-mediated rejection pathways. In addition, it evaluates five major mitigation strategies: GGTA1-knockout pigs, enzymatic α-galactosidase treatment, RNA interference, decellularization, and immunosuppressive approaches, including CD40-CD154 blockade and topical tacrolimus. Preclinical studies have demonstrated that GTKO corneas can maintain transparency for longer than 1 year, whereas decellularized matrices preserve corneal architecture while exhibiting low antigenicity. These findings support the future clinical translation of porcine corneal xenotransplantation.

Keywords: Corneal transplantation; Xenotransplantation; Graft rejection; Galactose; Immunosuppressive agents.