Abstract
Purpose: :
To evaluate potential factors affecting the retinal nerve fiber layer thickness (RNFLT) as measured by Stratus Optical Coherence Tomography (OCT) in healthy subjects.
Methods: :
We collected Stratus–OCT data using three standard protocols including high and standard image resolution for assessment of the peripapillary RNFLT. Effects of age, gender, refractive error, axial length, lens nuclear color and opalescence, intra ocular pressure, and optic disk size were correlated to RNFLT using simple and multiple regression analyses.
Results: :
One eye each of 178 healthy subjects between 20 to 80 years of age was included. Forty–one percent represented a random sample of the Malmö population. In univariate analyses, age, refractive error, axial length, and lens nuclear color and opalescence affected the RNFLT significantly. In multivariate analyses only age in combination with refractive error, or with axial length, affected the RNFLT significantly. When adding refractive error to age the coefficient of determination, r2, increased by ∼ 50%, from 9.1 to 17.6% using the FAST RNFLT protocol. RNFLT decreased with 2.6 to 2.9µm per increasing decade of age, and increased by 1.5 to 1.8µm per increasingly more positive diopter of spherical equivalent using the three protocols and full circle measurements.
Conclusions: :
Normal RNFLT as measured by Stratus–OCT standard protocols was affected by both age and refractive status. The effect on global RNFLT of a difference in refractive error of 5 diopters corresponded to the effect of a difference in age of 30 years. Our results indicate that Stratus–OCT normative limits for RNFLT may be beneficially narrowed by correcting for refractive status.
Keywords: nerve fiber layer • imaging/image analysis: clinical • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)