Effect of New High-Resolution OCT Platform on Pressure-Dependent Changes in Lumen Dimensions of Collector Channel Ostia
Purpose
To describe a new OCT platform that permits identification of rapid pressure-dependent opening and closure of collector channel ostia (CCO) in synchrony with trabecular meshwork (TM) motion.
Methods
SD-OCT imaging of radial limbal segments of ex vivo non-human primate-nemestrina (4) and human (4) eyes from the surface of trabecular meshwork (TM). Segments mounted in a Petri dish and immersed in balanced salt solution. Cannula inserted into Schlemm’s canal (SC) Pressure and flow controlled with reservoirs or perfusion pump. A Matlab algorithm binarized 2D images. SC height and area at different pressures quantified with FIJI (ImageJ software). To assess anatomic appearance under comparable conditions of SC dilation SEM was performed on radial sections cut from each quadrant of the limbus of a nemestrina monkey following viscoelastic dilation of SC.
Results
Tissues surrounding CCOs generally attached at only one end, permitting motion. Each of 6 imaged CCOs exhibited clearly identifiable pressure-dependent changes. Following a pump-induced pulse transient, quantification provided a representative OCT graph of SC and CCO area demonstrating a closed lumen at t=0. SC area increased rapidly over time to >25,000 um2 at 150 msec, peaking at 30,000 um2 by 300 msec. Simultaneously, the CCO area increased to 2,200 um2 at 150 msec increasing to 5100 um2 at 300 msec. Highest mean velocity of lumen area ∆ was ~1.47 mm/sec for SC and ~0.43 mm/sec for the CCO, both occurring within the 1st 50 msec.
Conclusion
This newly developed OCT platform identifies rapid pressure-dependent changes in CCO area. Pressure-responsive CCO dimension changes provide a mechanism to control distal resistance properties and thus function as component of normal outflow regulation. Modification of tissue properties that permit CCO motion may provide a new treatment target in glaucoma.