The clinical PS-OCT (Fig. 1) system utilized a SS laser (HSL-1000 by Santec Corp., Komaki, Aichi, Japan) with a sweep rate of 28 kHz, 1064-nm center wavelength, and a spectral scan range of 80 nm, providing an axial resolution of 12 μm in tissue, which is poorer than expected due to dispersion and deviations from a Gaussian-shaped laser power spectral density profile. A polarization controller consisting of a linear polarizer and a phase modulator is utilized to provide three incident polarization states into the interferometer. The phase modulator is composed of two lithium niobate () crystals with fast and slow axes oriented at 45 deg to the linear polarizer. The two crystals are of equal length and the fast axis of one is coaligned with the slow axis of the other to balance intrinsic birefringence and remove PMD. A high-voltage amplifier controls the phase retardation in the two crystals. The voltage applied to the phase modulator is adjusted to provide three polarization states with Stokes vectors in the right-handed laboratory frame (LF) being (1, 0, 0), (, 0, sin 60 deg), and (, 0, ).22 In the LF, the horizontal axis is along , vertical (along gravity) is along , and the light propagates along the -direction. A 30/70 fiber coupler splits source light into sample and reference arms. In the sample arm, an interface simultaneously delivers OCT light (0.86 mW average power) together with a line-scanning laser ophthalmoscope light onto the patient’s cornea. Light in the reference arm has two paths: one is connected to a balanced detection module to interfere with sample light and the other splits into system trigger and an electronic circuit for a resampling clock. A Mach–Zehnder interferometer is used to generate a resampling clock signal and is connected to an external circuit board to quadruple the clock frequency. Light reflected from the sample interferes with reference light in a bulk optics-balanced detection module. Reference light goes through a polarizer oriented at 45 deg to the vertical () axis before interfering to ensure equal intensity and zero-phase delay in horizontal and vertical polarization states. A nonpolarizing crystal beam splitter is used for balanced detection, and two polarization beam splitters separate interference signals into vertical and horizontal channels. The bulk optics-balanced detection module used for polarization detection eliminates unbalanced polarization transformations between the two detection arms.