The in vivo correlation between retinal pigment epithelium thickness and quantitative fundus autofluorescence in a Caucasian population

Purpose: To investigate the influence of age on the thickness of the retinal pigment epithelium/Bruch's membrane complex (RPE/Bruch's complex) and the quantitative autofluorescence (qAF) and to study the possible correlation existing between these two parameters in a healthy Caucasian population. Design: cross-sectional, observational study PARTICIPANTS: Healthy Caucasian volunteers between 18 and 65 years of age METHODS: All subjects underwent Spectral Domain Optical Coherence Tomography (SD-OCT) and qAF imaging with Heidelberg HRA-Spectralis. SD-OCT images were analyzed using the inbuilt graph-based automatic segmentation algorithm for single retinal layers identification to assess RPE/Bruch's complex thickness in vivo. The thickness values of both inner and outer rings of the Early Treatment Diabetic Retinopathy Study (ETDRS) grid, generated by the software using the "RPE" segmentation, were averaged to obtain a single RPE/Bruch's complex thickness value in each eye. Quantitative autofluorescence images were also evaluated using a dedicated software. The qAF values of eight subfields forming a ring centered onto the fovea were collected and averaged in order to obtain a single qAF value (qAF8) in each eye. The correlation between the RPE/Bruch's complex thickness, the qAF value and the age of the subjects was investigated. Main outcome measures: the in vivo correlation between RPE/Bruch's complex thickness and qAF RESULTS: A total of 105 eyes from 105 subjects (mean age 42.1±13.9 years, range 18-65) were included in the analysis. The mean RPE/Bruch's complex thickness significantly increased with age (r=0.33, P=0.0006). The values of qAF were also positively increased with age (P<0.0001). A significant correlation was found between qAF and RPE/Bruch's complex thickness (r=0.27, P=0.004). After adjusting for age, iris color and gender, the correlation remained significant only for subjects younger than 40 years of age (P=0.009). Conclusions: The RPE/Bruch's complex thickness increased with age in a healthy Caucasian population. A similar increase was found for qAF values. After adjusting for age and iris color, qAF and RPE/Bruch's complex thickness were still correlated in subjects younger than 40 years. The RPE/Bruch's complex thickness could reflect the lipofuscin/melanolipofuscin accumulation in normal subjects, adding great interest in RPE cell biology.