Longitudinal changes in retinal nerve fiber layer thickness in a healthy caucasian population

Purpose To study the loss of retinal nerve fiber layer thickness over time in healthy subjects. Methods In this prospective longitudinal study 65 female and male subjects (age 62.7 ± 10.6 years) were included. In the present study an optic disc cube scan protocol was employed to measure RNFLT using the Cirrus HD-OCT. The OCT scans were repeated in intervals between 3 and 6 months, the number of OCT scans was between 3 and 11 and the average observation period was 30 months. Linear mixed models were used to fit OCT data. Results On average a loss of RNFLT was seen during the average observation period. In a multiple regression model two factors influenced the results: age and baseline RNFLT. The greater the RNFLT value at baseline the stronger the loss of RNFLT. When dividing the subjects into 2 age groups a decrease in RNFLT was only seen in older subjects (70.2 ± 6.1 years), but not in younger subjects (55.1 ± 8.6 years). This decrease of average RNFLT in the older age group was −0.61 μm/year (95% confidence interval −1.10 μm/year to −0.11 μm/year). Conclusions The present study indicates a loss of RNFLT thickness over time in healthy subjects. This decrease was seen in older subjects, but not in younger individuals. The age-dependent loss of RNFLT should be considered when progression is analyzed in patients with neurodegenerative diseases such as glaucoma, multiple sclerosis or Alzheimer's disease.