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Hannah Kersten, Stuti Misra, Richard H Roxburgh, Helen V Danesh-Meyer, Charles NJ McGhee; Corneal Sub-Basal Nerve Plexus Density in Parkinson’s Disease. Invest. Ophthalmol. Vis. Sci. 201657(12):.
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The objective of this case-control study was to examine the ocular surface in patients with moderately severe Parkinson’s disease, including confocal microscopy of the corneal sub-basal nerve plexus. Blink abnormalities, including reduced blink rate are frequently reported in Parkinson's disease. Additionally, non-motor involvement, including visual system abnormalities, is now recognised as an important feature of the disease.
Fifteen patients with moderately severe Parkinson’s disease (Hoehn and Yahr grade 3 or 4) and fifteen controls were recruited. Participants were excluded if they had any condition that could affect sub-basal nerve density. Ophthalmic assessment included slit-lamp examination, non-invasive tear break up time, tear stability and lipid layer thickness, tear quantity, central corneal aesthesiometry, in vivo corneal confocal microscopy (to measure corneal sub-basal nerve density) and blink rate assessment. One eye of each patient was included in statistical analysis. Autonomic dysfunction was assessed using the Survey of Autonomic Symptoms.
Of the 15 Parkinson’s disease patients, ten were male and the mean age was 65.5 ± 8.6 years. Control participants were matched for age and gender. Four patients had a Hoehn and Yahr grading of 4, and 11 patients grade 3. The sub-basal nerve plexus density was reduced in patients with Parkinson’s disease compared with control participants (7.56 ± 2.4 mm/mm2 vs. 15.91 ± 2.6 mm/mm2, p<0.0001). There was no statistical difference in corneal sensitivity (p = 0.12), tear quantity (p =0.76) or tear stability (p = 0.10) between patients and controls. Lipid layer thickness was reduced in the Parkinson’s disease group (p = 0.02). There was a significant positive correlation between blink rate and sub-basal nerve density, although this was primarily due to the presence of an outlier. There was not a significant relationship between sub-basal nerve density and autonomic dysfunction.
This is the first study to report a reduction in corneal sub-basal nerve density in Parkinson’s disease, suggesting peripheral nervous system involvement. Parkinson’s disease has previously been thought to be a central nervous system disorder, although more recently there have been a number of reports providing evidence of peripheral neuropathy in the disease. The pathogenic mechanisms underlying peripheral neuropathy in Parkinson’s disease are not yet fully understood.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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