Age-related macular degeneration (AMD) is a major cause of severe visual loss among older people in developed countries.1
In AMD, the severe loss of central vision is often attributed to exudative lesions. Accurate investigation of exudative lesions is crucial for accurate evaluation and treatment of exudative AMD.
Polarimetry techniques have been developed to emphasize selectively the different layers of the retina. The most typical polarimetry technique used in ophthalmology is scanning laser polarimetry for glaucoma diagnosis.2,3
In the original conceptualization, the retardation of the retinal nerve fiber layer is estimated using the light returning from the ocular fundus.3,4
More recently, customized software to analyze data from scanning laser polarimetry was developed to investigate the polarization properties of macular disease.5,6
Multiply scattered light, which helps visualize the retinal pigment epithelial (RPE) layer and deep retinal lesions, was emphasized by detecting depolarized light and rejecting light that retains polarization.5–11
Phase-retardation maps were used to detect abnormal fibrotic changes in the retina.6
The borders of well-defined choroidal neovascular membrane (CNV) were clearly defined in the depolarized light image.6
Thus, scanning laser polarimetry has some potentiality to evaluate the macular disease. However, it does not provide depth-resolved information about the polarization properties of the retina. Therefore, the depth of the origin of the polarization change has not yet been demonstrated.
Optical coherence tomography (OCT) is a widely used imaging tool in ophthalmology,12
especially for retinal disease accompanied by morphologic changes, including AMD. Depth-resolved information about polarization has been obtained using polarization-sensitive optical coherence tomography (PS-OCT).13,14
Birefringence of the nerve fiber layer15
and polarization scramble at the retinal pigment epithelium16
were measured with time-domain PS-OCT, but three-dimensional measurements were limited because of the scanning speeds of these systems. Recently, dramatic advances in OCT technology17,18
have facilitated improvements in three-dimensional PS-OCT measurements. PS spectral-domain OCT (PS-SD-OCT)19–22
allows the collection of three-dimensional retinal information about polarization properties.19
The combination of scanning laser polarimetry and PS-SD-OCT offers a variety of possibilities for diagnosis. For instance, using the en face image of PS-SD-OCT, a direct comparison between scanning laser polarimetry and PS-SD-OCT is possible. Further, the origin of polarization changes in scanning laser polarimetry images can be detected and quantified with PS-SD-OCT. Structures seen in the scattered light images can be further probed in depth with PS-SD-OCT to determine the spatial relation of highly reflective structures or increased birefringence seen in PS-SD-OCT to a focal increase in scattered light in scanning laser polarimetry. Therefore, in this study, we compared scanning laser polarimetry images and PS-SD-OCT images of the same eyes to evaluate the birefringence properties of retinas with exudative AMD.