Spectral-Domain OCT Measurements in Alzheimer's Disease: A Systematic Review and Meta-analysis.

Topic OCT is a noninvasive tool to measure specific retinal layers in the eye. The relationship of retinal spectral-domain (SD) OCT measurements with Alzheimer’s disease (AD) and mild cognitive impairment (MCI) remains unclear. Hence, we conducted a systematic review and meta-analysis to examine the SD OCT measurements in AD and MCI. Clinical Relevance Current methods of diagnosing early AD are expensive and invasive. Retinal measurements of SD OCT, which are noninvasive, technically simple, and inexpensive, are potential biomarkers of AD. Methods We conducted a literature search in PubMed and Excerpta Medica Database to identify studies published before December 31, 2017, that assessed the associations between AD, MCI, and measurements of SD OCT: ganglion cell–inner plexiform layer (GC-IPL), ganglion cell complex (GCC), macular volume, and choroidal thickness, in addition to retinal nerve fiber layer (RNFL) and macular thickness. We used a random-effects model to examine these relationships. We also conducted meta-regression and assessed heterogeneity, publication bias, and study quality. Results We identified 30 eligible studies, involving 1257 AD patients, 305 MCI patients, and 1460 controls, all of which were cross-sectional studies. In terms of the macular structure, AD patients showed significant differences in GC-IPL thickness (standardized mean difference [SMD], –0.46; 95% confidence interval [CI], –0.80 to –0.11; I 2  = 71%), GCC thickness (SMD, –0.84; 95% CI, –1.10 to –0.57; I 2  = 0%), macular volume (SMD, –0.58; 95% CI, –1.03 to –0.14; I 2  = 80%), and macular thickness of all inner and outer sectors (SMD range, –0.52 to –0.74; all P 2  = 89%) and choroidal thickness (SMD range, –0.88 to –1.03; all P Conclusions Our results confirmed the associations between retinal measurements of SD OCT and AD, highlighting the potential usefulness of SD OCT measurements as biomarkers of AD.