OCT in Alzheimer's disease: thinning of the RNFL and superior hemiretina.

BACKGROUND: Peripapillary retinal nerve fiber layer (pRNFL) and internal macular layer thinning have been demonstrated in Alzheimer's disease (AD) with optical coherence tomography (OCT) studies. The purpose of this study is to compare the pRNFL thickness and overall retinal thickness (RT) in AD patients with non-AD patients, using spectral domain optical coherence tomography (SD-OCT) and determine the sectors most characteristically affected in AD. METHODS: A cross-sectional study was performed to determine the pRNFL and overall macular RT thicknesses in AD and non-AD patients, attending a tertiary hospital center. For pRNFL, the global and six peripapillary quadrants were calculated, and for overall RT values, the nine Early Treatment Diabetic Retinopathy Study (ETDRS) areas were used. A multiple regression analysis was applied to assess the effects of disease, age, gender, spherical equivalent, visual acuity, intraocular pressure, axial length and blood pressure on pRNFL and overall macular RT. RESULTS: A total of 202 subjects, including 50 eyes of 50 patients with mild AD (mean age 73.10; SD = 5.36 years) and 152 eyes of 152 patients without AD (mean age 71.03; SD = 4.62 years). After Bonferroni correction, the pRNFL was significantly thinner for the AD group globally and in the temporal superior quadrant (10.76 µm and 20.09 µm mean decrease, respectively). The RT thickness was also decreased in superior sectors S3 and S6 (mean thinning of 9.92 µm and 11.65 µm, respectively). Spearman's correlation coefficient showed a direct association between pRNFL in the temporal superior quadrant and RT in superior S6 and S3 sectors (rS = 0.41; p < 0.001 and rS = 0.28; p < 0.001, respectively). CONCLUSIONS: Patients with AD showed a significant thickness reduction in global and temporal superior quadrants in pRNFL and in superior pericentral and peripheral sectors of RT. These findings may reflect a peripapillary and retinal changes characteristic of AD, suggesting the importance of SD-OCT as a potential adjuvant in early diagnosis of AD. Further studies are needed to understand which retinal layers and macular sectors are more useful as potential ocular biomarker over time in AD.

Choroidal thinning: Alzheimer's disease and aging.

INTRODUCTION: The purpose of this study was to measure and to compare macular choroidal thickness (CT) between patients with mild Alzheimer's disease (AD), patients without AD, and elderly patients. METHODS: CT was measured manually in 13 locations at 500-µm intervals of a horizontal and a vertical section from the fovea. Linear regression models were used to analyze the data. RESULTS: Fifty patients with a diagnosis of mild AD (73.1 years), 152 patients without AD (71.03 years), and 50 elderly without AD (82.14 years) were included. In the AD patients, CT was significantly thinner in all 13 locations (P < .001-comparing with age-match group), and comparing with the elderly group, a more pronounced difference was found in two locations temporal to the fovea. DISCUSSION: Patients with AD showed a significant choroidal thinning even when compared with elderly subjects. The reduction of CT may aid in the diagnoses of AD, probably reflecting the importance of vascular factors in their pathogenesis.