Because diagnosing Alzheimer’s disease (AD) currently involves invasive and expensive testing, researchers are on the hunt for better options. And they may have found their answer in the eye.

While research has sporadically linked retinal measurements using spectral-domain optical coherence tomography (SD-OCT) with AD and mild cognitive impairment (MCI), the exact relationship remains unclear.

Researchers took a closer look at 30 studies, with a total of 1,257 AD patients, 305 with MCI and 1,460 controls, to better understand SD-OCT’s role in AD screening and diagnosis. They found patients with AD had significant differences in their ganglion cell-inner plexiform layer thickness (a mean difference of -0.46), ganglion cell complex thickness (mean of -0.84), macular volume (-0.58) and macular thickness of all inner and outer sectors (SMD ranged -0.52 to -0.74) compared with controls. Peripapillary retinal nerve fiber layer thickness and choroidal thickness were also thinner in AD.

“Our results confirmed the associations between retinal measurements of SD-OCT, and AD, highlighting the potential utility of SD-OCT measurements as biomarkers of AD,” the study concludes.

Chan VTT, Sun Z, Tang S, et al. Spectral domain-optical coherence tomography measurements in Alzheimer’s disease: a systematic review and meta-analysis. Ophthalmology. August 13, 2018. [Epub ahead of print].