Roughness of retinal layers in Alzheimer’s disease

Abstract

There is growing evidence that thinned retinal regions are interspersed with thickened regions in all retinal layers of patients with Alzheimer’s disease (AD), causing roughness to appear on layer thickness maps. The hypothesis is that roughness of retinal layers, assessed by the fractal dimension (FD) of their thickness maps, is an early biomarker of AD. Ten retinal layers have been studied in macular volumes of optical coherence tomography from 24 healthy volunteers and 19 patients with mild AD (Mini-Mental State Examination 23.42 ± 3.11). Results show that FD of retinal layers is greater in the AD group, the differences being statistically significant (p < 0.05). Correlation of layer FD with cognitive score, visual acuity and age reach statistical significance at 7 layers. Nearly all (44 out of 45) FD correlations among layers are positive and half of them reached statistical significance (p < 0.05). Factor analysis unveiled two independent factors identified as the dysregulation of the choroidal vascular network and the retinal inflammatory process. Conclusions: surface roughness is a holistic feature of retinal layers that can be assessed by the FD of their thickness maps and it is an early biomarker of AD.

A Systematic Review on Retinal Biomarkers to Diagnose Dementia from OCT/OCTA Images

“…Moreover, the outcomes of [69] indicated a significant thinning of macular RNFL (mRNFL), GCL, IPL, and ONL for AD contrasted with HCs. The results in [42] align with those in [47], indicating that a pronounced thinning of macular layers mRNFL, INL, and OSL is related to mild AD rather than to HCs. Although both works by [92] and [42] agreed that a noteworthy thinning of GCL and IPL layers is associated with mild AD unlike HCs; however, the findings of [47] is conflicting such that the thickness changes of both GCL and IPL layers were insignificant between both groups.…”

“…The results in [42] align with those in [47], indicating that a pronounced thinning of macular layers mRNFL, INL, and OSL is related to mild AD rather than to HCs. Although both works by [92] and [42] agreed that a noteworthy thinning of GCL and IPL layers is associated with mild AD unlike HCs; however, the findings of [47] is conflicting such that the thickness changes of both GCL and IPL layers were insignificant between both groups. The results reported in [17] agreed with [33] such that a notable thickness reduction of GCC layer is associated with MCI or aMCI rather than HCs.…”

“…Changes to the full retinal thickness (FRT), defined from the ILM to the top of RPE, failed to distinguish between tAD in [56], AD in [69], mild AD in [42,47], MCI in [85], aMCI in [65], EOAD in [90], FTD in [79,80], against HCs. Additionally, when multiple classes were involved in the analysis, the FRT variations were negligible between the three groups (mild AD, moderate AD, HCs) in [76], and between (aMCI, AD, HCs) in [67].…”

Association between retinal markers and cognition in older adults: a systematic review

“…This is consistent across all types of OCT devices. Our findings indicate that thinning of the RNFL and pRNFL may be associated with poorer cognitive function, however, within the last decade, studies have found more varied results for pRNFL, with only 6 (out of 21, 28.6%) studies identifying an association 13 26–30. On the other hand, 45.5% of studies using OCT devices to measure RNFL thickness have identified a positive correlation with cognitive impairment, although studies with larger sample sizes (eg, Sánchez et al ,31 930; van de Kreeke et al ,32 298) found no significant correlation.…”