Retinal birefringence scanning (RBS) is a method for detecting the central fixation of the eye.
By simultaneously measuring the central fixation of both eyes, small- and large-angle strabismus can be detected.
RBS uses the human eye's birefringent properties to identify the position of the fovea and the direction of gaze, and thereby to measure any binocular misalignment.
Birefringent material has a refractive index that depends on the polarization state and propagation direction of light.
These fibers (named after Friedrich Gustav Jakob Henle) are photoreceptor axons that are arranged in a radially symmetric pattern, extending outward from the fovea, which is the most sensitive part of the retina.