Researchers in the Doheny Eye Institute in Los Angeles, US, have published a study on marked pathological tissues in the retinal nerve fibre layers (RNFL) with Alzheimer’s disease (AD). While several previous studies have reported on OCT research from AD patients in the retina, the current reports indicate that clinical utility of the retina as a purported biomarker for AD remains to be inconclusive. One of the challenges for the research have various limitations, including the reduced cooperation from cognitively compromised patients and in advanced clinical stages. Alternatively, an ex vivo approach may be valuable in using human postmortem tissue in order to examine a more precise and quantitative assessment of the retina. In a current approach, researchers here have confirmed that, “quantified histopathologic findings provide a more comprehensive understanding of the retina in AD than previously reported”.
In the study, researchers stated that results have identified the first quantitative thickness assessment of the inner and outer layers of the retina using postmortem human tissues from AD. The results showed that tissues were histopathologically confirmed for amyloid deposition and were derived from patients neuropathologically confirmed for severe AD. Formally, results outlined that RNFL thinning supero-temporally was significant closest to the optic nerve (∼35% thickness reduction; P < 0.001), while supero-nasally, RNFL was thinner throughout all points (∼40% reduction; P < 0.001). In addition, supero-temporally, RGCL (retinal ganglion cell layer) thinning was pronounced toward the macula (∼35% thickness reduction; P < 0.001), and supero-nasally, RGCL also showed uniform thinning throughout (∼35% reduction; P < 0.001). Furthermore, IPL (inner plexiform layer) thinning supero-temporally was statistically significant in the macula (∼15% reduction; P < 0.01) and supero-nasal IPL featured uniform thinning throughout (∼25% reduction; P < 0.001). Supero-temporally, INL (inner nuclear layer) and ONL (outer nuclear layer) thinning were pronounced toward the macula (∼25% reduction; P < 0.01), and supero-nasally, INL and ONL were thinner throughout (∼25% reduction; P < 0.01).
In essence, the researchers have found that “significant thinning for all assessed retinal layers and observed differences in thickness by layer and by region, supero-nasally and superotemporally with respect to the optic nerve”. In their discussion, the researchers on their paper commented that, “given mounting evidence that alterations in the visual system may precede cognitive changes, such a quantitative means of assessing disease may serve useful for ultimately monitoring disease, which may permit earlier interventions”. The morphometric data in this study may potentially recognize the caged canary in the coal mine and this may help to develop any tools to in retinal biomarkers that may assist to Alzheimer’s disease research.