Purchase this article with an account.
Dean A. Van Nasdale, Ann E. Elsner, Timothy Hobbs, Stephen A. Burns; Macular Birefringence Changes in Normal Aging. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5280.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To use custom scanning laser polarimetry (SLP) imaging to examine and quantify normal age-related changes to the photoreceptor axons in the central macula using the birefringent properties of the Henle fiber layer.
A scanning laser polarimeter (GDx, LDT/CZM) was used to acquire 15 degree macular images (256 x 256 pixels) in 120 clinically normal subjects. 10 male and 10 female subjects were selected for each decade, ranging in age from the third decade through the eighth. Raw image data were used to compute macular cross phase retardation maps associated with Henle fiber layer in the central macula. Annular regions of interest ranging from 0.25 to 3 degrees eccentricity centered on the fovea were used to generate intensity profiles from the phase retardation data, which were then analyzed using fast fourier transform (FFT). The second harmonic component of the FFT (2f FFT) was normalized to the remaining FFT components and linear regression was used to examine the location of the maximum normalized 2f eccentricity. This normalization minimized the effect of unrelated ocular polarization properties, such as those from the cornea. The normalized 2f component, which fell between 1 and 1.25 degrees was also evaluated as a function of age using linear regression. Analysis of variance (ANOVA) comparisons of refractive error, used as a surrogate measure of axial length, ensured that there were no potential differences in due to axial length-related thinning among the different subjects categorized by decade.
The eccentricity of the maximum normalized 2f FFT was significantly increased as a function of age (R2 = 0.066, ß = 0.256, p = 0.005), indicating alterations in the axons of the central photoreceptors relative to those in the parafovea in older subjects. The normalized 2f FFT component, averaged between 1 and 1.25 degrees, decreased as a function of age (R2 = 0.213, ß = -0.462, p < 0.001), indicating changes in the cone photoreceptor axons in the central macula in older subjects. Refractive error measurements did not differ among the different decades (ANOVA, p = 0.431).
The birefringence changes in the central macula indicate structural alterations in the cone photoreceptor axons near the fovea as a function of age. Despite individual differences among subjects of similar ages, this large sample size demonstrates systematic changes to the central cone photoreceptor morphology using SLP imaging.
This PDF is available to Subscribers Only