Polarization Variability in Age-related Macular Degeneration

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Abstract

SIGNIFICANCE

Age-related macular degeneration (AMD) is a leading cause of irreversible vision loss. Complementary imaging techniques can be used to better characterize and quantify pathological changes associated with AMD. By assessing specific light-tissue interactions, polarization-sensitive imaging can be used to detect tissue disruption early in the disease process.

PURPOSE

The aim of this study was to compare variability in central macular polarization properties in patients with nonexudative AMD and age-matched control subjects.

METHODS

A scanning laser polarimeter (GDx, LDT/CZM) was used to acquire 15 × 15-degree macular images in 10 subjects diagnosed with nonexudative AMD and 10 age-matched control subjects. The coefficient of variation (COV, SD/mean) was used to quantify variability in pixel intensity in the central 3.3° of the macula for custom images emphasizing multiply scattered light (the depolarized light image) and polarization-retaining light (the maximum of the parallel detector image). The intensity COV was compared across subject categories using paired t tests for each image type.

RESULTS

The COV in the central macula was significantly higher in the AMD subject group (average, 0.221; 95% confidence interval [CI], 0.157 to 0.265) when compared with matched control subjects (average 0.120; 95% CI, 0.107 to 0.133) in the depolarized light image (P = .01). The COV in the maximum of the parallel detector image was not statistically different between the two subject groups (AMD average, 0.162 [95% CI, 0.138 to 0.185]; control average, 0.137 [95% CI, 0.115 to 0.158]; P = .21).

CONCLUSIONS

Variability in multiply scattered light is higher than that of light that is more polarization preserving in patients with nonexudative AMD. Multiple scattering may act as an early indicator representing disruption to the macula in early AMD.

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