Systematic dispersion compensation for spectral domain optical coherence tomography using time-frequency analysis and iterative optimization for iridocorneal angle imaging

Abstract: Dispersion is a common phenomenon in optics due to the frequency dependence of the refractive index in polychromatic light. This issue, if left untreated in optical coherence tomography (OCT) imaging, leads to signal broadening of the coherence length and deterioration of the axial resolution. We report a new numeric method for the systematic dispersion compensation in a spectral-domain (SD) OCT for imaging the iridocorneal angle of human cadaver eyes. The dispersion compensation for our OCT system is calculated by an automated iterative process that minimizes the wavenumber-dependent variance of the ridge extracted from the energy distribution of a mirror's spectral interferogram using Short-Time Fourier Transform (STFT) Time-Frequency Analysis (TFA). The average axial resolution of 2.7 um in air was achieved at a range of depths up to 2 mm. Compensated OCT images of the iridocorneal angle in human cadaver eyes were much clearer than non-compensated images. We demonstrate the feasibility, effectiveness, and robustness of the proposed method for dispersion compensation in an SD-OCT by evaluating both the mirror and human cadaver eye measurements. We also verified that our imaging system is able to visualize the iridocorneal angle details, such as trabecular meshwork (TM), Schlemm's canal (SC), and collector channels (CCs), which are important ocular outflow structures and play a crucial role in glaucoma managements.