Exploring retinal layer alterations in mild cognitive impairment: A pilot oct study

Aims/Purpose: In the last decades, retinal alterations have been shown by OCT in Alzheimer's disease (AD), initially affecting the macular region in early AD, and subsequently progressing to the peripapillary retina, pointing out this tissue to be considered for diagnosis and follow-up in AD. This study aimed to investigate retinal changes in patients with mild cognitive impairment (MCI), an intermediate stage between normal aging and AD, to know if in this preclinical stage there are changes in the retina.

Methods: Sixteen healthy subjects and 16 MCI patients were included. All participants underwent comprehensive ophthalmic evaluation and macular OCT (SD-OCT, Heidelberg, Germany) to assess retinal structure. The thickness of each retinal layer in the macular area was measured using the OCT software, with manual verification and modification of segmentation if necessary. Thicknesses of retinal layers, including retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), and retinal pigment epithelium (RPE), were analyzed. The inner and outer macular rings were evaluated according to the standard macular grid of the Early Treatment Diabetic Retinopathy Study (ETDRS). Statistical analysis was performed using two-way ANOVA with Tukey´s multiple comparison test.

Results: Individuals with MCI exhibited significant thinning in the OPL in the inner ring of the superior sector (p < 0.01), along with significant thickening in the ONL in the same area (p < 0.05) compared to controls. Additionally, a trend towards thinning in the inner retinal layers was observed in the MCI group.

Conclusions: While in the inner retinal layers it was shown a thinning, it is noteworthy that in the ONL it was shown a thickening. OCT holds promise as a non-invasive tool for MCI screening. Further research with larger sample sizes is warranted to validate and expand upon these findings.