Identifying Collector Channel Orifices In Vivo with Phase-Sensitive Optical Coherence Tomography: A Preliminary Study

Collector channels are openings located in the trabecular meshwork (TM) of the human eye that function as conduits, connecting the anterior chamber to the episcleral veins. Identifying the positions of collector channel orifices (CCOs) is essential for positioning implants in microinvasive canal-based glaucoma surgery, which is still not possible in vivo currently. Considerable evidence indicates that aqueous outflow becomes more active near the CCOs. Because the TM movement regulates the aqueous outflow, identification of the TM motion signal has the potential to locate the CCOs. Phase-sensitive optical coherence tomography (PhS-OCT) is an effective tool for the instantaneous detection of TM motion in vivo with sensitivity at the nanometer scale. However, the downside of this method is that phase measurement is prone to mix noises that negatively distinguish between biomedical signals. The TM motion was considered initially to be set up by the cardiac pulse. In this paper, a signal quality index related to blood pressure monitoring was applied to assess the validity of the TM motion signal. Measurements were carried out on two pairs of healthy human eyes. Quantitative measurements of the TM motion signal region such as size and frequency were recorded as the judgment indicator for CCOs. These results demonstrate that the PhS-OCT is a valuable tool capable of revealing the aqueous outflow pathway in vivo, offering a novel alternative to optimize glaucoma surgery.