Emerging frontiers for structured light in polarization perception and retinal diagnostics [Invited]

The entoptic phenomena of Haidinger’s and Boehm’s brushes provide a noninvasive window into the structural and functional organization of the human retina. These percepts arise from polarization-dependent interactions within distinct retinal layers: radial diattenuation by macular pigments in the fovea produces Haidinger’s brushes, whereas polarization-sensitive scattering in the non-foveal retina gives rise to Boehm’s brushes. Recent advances in structured light have introduced spin–orbit beams with spatially varying polarization fields that conform to the intrinsic symmetry of retinal polarization interactions, enabling systematic expansion and enhancement of these entoptic patterns. By aligning the optical field topology with retinal architecture, such beams generalize the formation of Haidinger’s and Boehm’s brushes to complex multi-lobed geometries and provide a path toward quantitative mapping of perceptual structure across eccentricity. This review outlines the optical and biological foundations of polarization perception, summarizes recent results demonstrating its enhancement through spin–orbit structured illumination, and describes psychophysical methods for characterizing stimulus geometry, contrast sensitivity, and retinal dependence. Finally, it highlights how these techniques establish a framework for functional retinal mapping and potential future diagnostic applications capable of detecting disruptions associated with central or non-foveal retinal disease.