Relationship between foveal birefringence and visual acuity in neovascular age-related macular degeneration

Abstract

Purpose To investigate the relationship between visual acuity and foveal birefringence in patients with neovascular age-related macular degeneration. Methods In total, 40 patients with choroidal neovascularization underwent macular imaging with scanning laser polarimetry. Bowtie patterns, typically seen in birefringence images of the macula, were evaluated and classified into three categories: (1) regular bowtie present; (2) bowtie present, but disrupted; and (3) no bowtie present. The relation of the bowtie appearance to the best-corrected logMAR visual acuities was tested (ANOVA). Results Mean visual acuity was best for the group that had regular bowties (mean logMAR ¼ 0.34) and differed statistically significantly from the disrupted bowtie group and no bowtie group (P ¼ 0.01 and 0.0007). Ages for the three groups did not differ (P ¼ 0.31). Conclusions Appearance of a regular bowtie indicates a substantially intact Henle fibre layer with the potential for good visual function, despite the presence of underlying pathology. Conversely, disruption or absence of a bowtie may indicate severe damage to the photoreceptors, consistent with the finding of poorer visual acuity.

Henle fiber layer phase retardation measured with polarization-sensitive optical coherence tomography

“…Arc angles θ 1 and θ 2 are used to calculate DPPR (see Eq. (2). Polarization states at the reference (I 1 and I 2 ) are shown noisier (larger Δθ) than states at the IS/OS (I 1 ' and I 2 ' ) to reflect the lower SNR.…”

“…Aging and macular diseases such as age-related macular degeneration and diabetic retinopathy are known to disrupt the organization of these fibers and reduce layer birefringence [2,3]. Since disruption indicates structural changes to otherwise well-ordered neural tissues, birefringence measurements may serve as a sensitive indicator of disease onset.…”

Foveal phase retardation changes associated with normal aging

“…Improved contrast has also improved the ability to delineate pathological features in diseases such as epiretinal membranes (Miura et al, 2007); drusen (Burns et. al., 2003); changes near the optic nerve head (Mellem-Kairala et al, 2005); exudative age-related macular degeneration (Elsner et al, 2007; Miura et al, 2008; Weber et al, 2007); and central serous chorioretinopathy (Miura et al, 2005). …”

Digital micromirror device based ophthalmoscope with concentric circle scanning

“…As we currently are a factor of 4 below the maximum permissible exposure according to the IEC standard 60825-1 [21], there is still considerable room for further improvement. The polarisation optics to reduce the stray reflections in the system lead to polarisation artefacts in the images due to birefringence of the cornea [34] and retina [29], influencing the images being recorded…”

“…6D. This structure occurs around the fovea due to a meridional variation in birefringence exhibited by Henle's fibres surrounding the fovea [29]. The different regions (Figs.…”