Abstract
Purpose :
Fshape is a mathematical framework that can register multiple retinal surfaces and values mapped on the surfaces (e.g., thickness) to a common template. This allows for detailed, point-wise statistics across groups and time-points. Using Fshape, we examined the macular RNFL thickness (mRNFLT) between cognitively normal (CN) subjects, subjects with mild cognitive impairment (MCI), and Alzheimer’s disease (AD) patients.
Methods :
We compared 8 eyes from CN subjects, 4 eyes from MCI subjects, and 6 eyes from AD patients, which were imaged with SD-OCT (Cirrus HD-OCT, Carl Zeiss Meditec Inc., Dublin, CA, USA). OCT volumes centered on the fovea were obtained in 6mmx6mm scan area with 200×200 A-scans. mRNFL was automatically segmented and measured for thickness. Fshape mean templates of mRNFLT were generated for each group and for i) CN vs AD, ii) MCI vs AD, and iii) CN or MCI vs AD for group-wise comparison.
Results :
Fig 1-A shows Fshape-mean mRNFLT maps for each group. All maps display the typical mRNFLT pattern of superior-inferior symmetry with thinner temporal and thicker nasal regions.
For CN vs AD comparison, Fig 1-B (top) shows point-wise group-mean mRNFLT residuals for CN (green) and AD (red), from nasal to temporal direction. The group-mean difference is plotted in Fig 1-B (middle) and on the mean mRNFL in Fig1-B (bottom). In most regions, CN group has greater mRNFLT than AD group, and the difference is the greatest in the nasal region surrounding the foveal pit. Similar plots are shown for MCI vs AD comparison in Fig 1-C, with the MCI (blue) showing overall thicker mRNFL than AD (red). In Fig 2, the residuals and difference are plotted for all non-AD (cyan) and AD subjects (red). Thinner mRNFL in AD subjects is marked in the nasal region surrounding the foveal pit. After Bonferroni correction, the group mean mRNFLT in AD group was significantly less than CN (p=.003), MCI (p<.001), and combined non-AD group (p<.001).
Conclusions :
We found differences in the mRNFL in AD subjects compared with CN and MCI subjects using a novel analysis (Fshape registration framework to generate mean templates within and across groups). The results show overall thinner mRNFL in AD subjects with detailed regional patterns not detectable by conventional statistical and sectoral comparison. Our analysis may provide further insights into subtle retinal changes in AD.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.