Abstract
Purpose: :
To use custom scanning laser polarimetry to detect and quantify the amount of retinal pathology associated with age-related macular degeneration (AMD). To distinguish pathological retinal changes associated with AMD from normal aging changes using polarization analysis.
Methods: :
A scanning laser polarimeter (GDx, LDT/CZM) was used to acquire 15 degree macular images (256 x 256 pixels) in 13 patients diagnosed with non-exudative AMD and 13 age and gender matched normals. Raw image data were used to compute 3 custom image types differing in polarization content. The fovea was located using a birefringence image. A 5deg by 5deg region of interest centered on the fovea was used to examine central retinal pathology, which was detected based on changes in a depolarized light image and a polarization preserving image. A paired t-test was used to compare the two images types among all subjects and to compare areas depolarization between AMD patients and matched normals. A subset of 3 subjects were imaged with spectral domain OCT to verify the relative depth and size of pathological features seen in SLP imaging.
Results: :
Pathologic features associated with AMD were detected using depolarized light imaging, and were more extensive in depolarized imaging compared to polarization preserving imaging. In both AMD subjects and matched normals, there were more areas of retinal irregularities in the depolarized light image than in the polarization preserving image (paired t-test, p<0.001). The areas of light depolarization in AMD subjects was significantly larger than matched normals (paired t-test, p<0.001) and appeared more coalesced. Highly depolarizing areas seen in AMD subjects correlated with pathology seen on SDOCT imaging.
Conclusions: :
Areas of pathology associated with AMD show characteristic polarization changes, specifically increased light scatter and depolarization. Greater amounts of light depolarization occur in AMD patients than in matched normals in the central 5deg of the macula. Coalesced areas of causing light depolarization changes are consistent with deep retinal pathological features typical of non-exudative AMD seen using SDOCT.
Keywords: imaging/image analysis: clinical • age-related macular degeneration • retina