Structured Light in Vision Science Applications

The dichroic macular pigment in the eye acts as a natural radial polarization filter and enables humans to directly perceive polarization-related entoptic phenomena. Linearly polarized blue light induces a subtle bowtie-like pattern known as Haidinger's brush in the central point of vision. The clarity and shape of this perceived pattern are directly linked to the health of the macula, rendering Haidinger's brush a potential diagnostic marker in research on early-stage age-related macular degeneration (AMD) and central field visual dysfunction. However, due to the faint nature of this signal, integrating the perception of Haidinger's brush into modern clinical methods remains a challenge. Here we review some advances in techniques to increase the strength of the perceived signal by employing polarization coupled orbital angular momentum states. We successfully achieved the creation of stimuli with higher numbers of azimuthal fringes, enabling the perception and discrimination of Pancharatnam-Berry phases, measuring the visual angle of entoptic phenomena, retinal imaging using structured light, and the creation of radially varying entoptic stimuli. Our current studies are focusing on applying the structured light methods that we developed to subjects that suffer from ocular diseases such as AMD.