Researchers have recently turned their attention to the retinal nerve fiber layer (RNFL) in the search for earlier screening tools for cognitive decline—and have uncovered promising results.

One group of investigators from the Netherlands used optical coherence tomography (OCT) to examine the RNFL and ganglion cell–inner plexiform layer (GC-IPL) thicknesses of 3,289 patients, 41 of whom were already diagnosed with dementia. They found an association between thinner GC-IPL and the prevalence of dementia with an odds ration of 1.37. In following the patients for a total of 14,674 person-years, the researchers further discovered an association between thinner RNFL at baseline and an increased risk of developing dementia.1

“Thinner RNFL is associated with an increased risk of dementia, including Alzheimer disease, suggesting that retinal neurodegeneration may serve as a preclinical biomarker for dementia,” the researchers conclude.1

A second team, from the United Kingdom (UK), conducted a community-based cohort study of 32,038 patients aged 40 to 69 years. Baseline baseline OCT imaging, a physical examination and four basic cognitive tests revealed an association between a thinner RNFL and worse cognitive performance. After controlling for potential cofounders, the researchers discovered those in the thinnest quintile of RNFL were 11% more likely to fail at least one cognitive test.2

Upon follow-up three years later with 1,251 patients, the researchers noted “participants with an RNFL thickness in the two thinnest quintiles were almost twice as likely to have at least one test score be worse at follow-up cognitive testing.”2

Echoing their colleagues in the Netherlands, these researchers conclude: “A thinner RNFL is associated with worse cognitive function in individuals without a neurodegenerative disease as well as greater likelihood of future cognitive decline. This preclinical observation has implications for future research, prevention, and treatment of dementia.”2

1. Mutlu U, Colijn JM, Ikram MA, et al. Association of retinal neurodegeneration on optical coherence tomography with dementia: a population-based study. JAMA Ophthalmol. June 25, 2018. [Epub ahead of print]. 
2. Ko F, Muthy ZA, Gallacher J, et al. Association of retinal nerve fiber layer thinning with current and future cognitive decline: a study using optical coherence tomography. June 25, 2018. [Epub ahead of print].