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Cirous Dehghani, Laura Elizabeth Downie, Shaun Frost, Rajiv Jayasena, Christopher Fowler, Colin L Masters, Yogesan Kanagasingam; In vivo corneal confocal imaging and its potential utility for Alzheimer’s disease: A feasibility study. Invest. Ophthalmol. Vis. Sci. 2019;60(9):6091.
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© ARVO (1962-2015); The Authors (2016-present)
The increasing number of studies employing in vivo confocal microscopy (IVCM) raise the hypothesis that corneal nerve abnormalities could serve as potential imaging biomarkers for a range of central and peripheral neurodegenerative diseases. The aim of this pilot study was to investigate the feasibility of conducting IVCM, and its potential usefulness to assess corneal nerve morphology in individuals with Alzheimer’s disease (AD) and mild cognitive impairment (MCI).
Fifteen participants were recruited from the Australian Imaging Biomarkers and Lifestyle (AIBL) study in Melbourne, Australia. The cohort consisted of 5 cognitively normal (CN) individuals, 5 with MCI, and 5 with AD. Participants underwent slit lamp examination of the anterior segment followed by IVCM imaging of the cornea using the HRT-3 device coupled with Rostock Cornea Module. Ocular surface integrity was assessed after the IVCM examination using fluorescein staining. An automated software (ACCMetrics) was used to derive quantitative data on corneal morphology, including nerve fiber length (CNFL), nerve fiber density (CNFD) and nerve branch density (CNBD).
IVCM was successfully performed in all participants, it was well tolerated and there were no adverse events. No significant ocular surface reaction or staining was observed following the procedure. The quantified corneal nerve morphometric parameters were trended towards a decrease in AD and MCI groups vs. CN participants. The mean ± SD of CNFL in CN, MCI and AD groups were 17.3 ± 4.6, 16.3 ± 2.6 and 13.7 ± 6.0 mm/mm2, respectively. The mean ± SD of CNFD and CNBD in CN group (27.8 ± 8.5 and 53.3 ± 20.5 no/mm2) were also found to be higher than those for MCI (24.4 ± 3.9 and 43.9 ± 26 no/mm2) and AD (22.5 ± 11.0 and 35.1 ± 18.9 no/mm2) individuals, respectively, but the differences did not reach statistical significance.
This feasibility study demonstrates that IVCM is a well-tolerated, non-invasive procedure that can be used to assess the corneal neural tissue in AD and MCI. Given our preliminary finding of potential corneal nerve deficits in AD and MCI, future large scale studies are warranted to further assess the utility of IVCM for detection of prodromal and clinical AD, as well as to investigate the potential relationship between corneal nerve morphology vs. cognitive impairment and the brain amyloid-β (Aβ) and tau burden in AD.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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