Abstract
Purpose:
Early markers are needed for experimental and clinical diagnosis and follow-up of Alzheimer disease (AD) and earlier stages as Mild Cognitive Impairment (MCI). Retinal Nerve Fiber Layer (RNFL) thinning have been observed in AD and MCI patients. We performed a prospective, observational clinical study to ascertain how RNFL thickness, as measured by Optical Coherence Tomography (OCT), can be correlated with different grades of cognitive impairment.
Methods:
All patients who came to our center during an open door initiative carried out between September and October of 2014 were invited to participate in neurological and complete neuropsychological examination, and then sorted between three different diagnostic groups: Healthy controls (C), MCI and AD. All patients who agreed undergone through a complete ophthalmological examination, including measurements of RNFL and macular thickness by OCT Model 3D OCT-1 Maestro (Topcon, Japan). All statistical analyses were performed using the Statistical Package for the Social Sciences (version 20.0; SPSS, Inc., Chicago, IL, USA)
Results:
200 eyes from 100 patients (38 Healthy controls, 41 MCI and 21 AD) were included . Mean age for the whole sample was 67 years (SD=10.46) and 59.5 years for Control group, 67.71 for MCI and 80.52 for AD. Those differences showed to be statistically significant with a p value <0.001. No differences were observed on Macular thickness between groups. RNFL measurements showed to be different for overall thickness (p<0.001), superior (p<0.001), temporal (p=0.002) and inferior (p=0.003) quadrants. Statistical significance dissapeared when age adjustment was applied, resulting the superior quadrant thickness values for each group (C=113.01µm, MCI=111.67µm, AD=100.95µm) to be marginally significant (p=0.070). When compared individually, AD group showed to be statistically different from C (p=0.037) and MCI (p=0.024) on upper quadrant, with no differences between MCI and Controls.
Conclusions:
Data suggests a tendency to RNFL thinning on AD patients. Nevertheless, age revealed to be the main factor related with RNFL thinning in our series. If OCT is an appropriate method for AD and MCI assessment, capable to discriminate between disease and normal age related changes on retinal thickness layers, need to be further evaluated.