Abstract
Purpose :
Schlemm’s canal (SC) and its surrounding limbal vascular network are key components of the conventional pathway. Production and outflow of aqueous humor control intraocular pressure (IOP), which is elevated in most glaucoma cases. The morphology of SC can vary significantly within an individual. Its size has been shown to correlate with the presence and severity of glaucoma as well as glaucoma surgeries. Therefore, a tool allowing visualization of the entire Schlemm’s canal in vivo can be invaluable. We apply visible-light OCT (vis-OCT) and vis-OCTA towards imaging the entire SC and its surrounding limbal vascular network in mouse for the first time.
Methods :
We developed a small animal vis-OCT system to image the entire SC and its surrounding vessels. A pair of angled mirrors were mounted to a motorized rotational stage and placed at the end of the sample arm to deflect the incident light beam. The angle was optimized for image quality. Eight raster scans were acquired, each after a 45-degree rotation of the stage. Vis-OCTA images were also acquired by repeating each B-scan five times. Two methods of perturbing the natural state of SC in wild-type mice were used: manometry to change the IOP and a suture tightened around the base of the eye to cause blood reflux into the SC.
Results :
Upon montaging all 8 raster scans, the entire area surrounding SC was visualized, with the limbal vessels clearly imaged by vis-OCTA in 3D (Fig 1). SC was visualized by vis-OCTA via blood reflux induced motion contrast. Differences in SC could be clearly detected through both methods of perturbing SC. Specifically, SC increased in size with lower IOP and decreased in size with higher IOP. The suture tightened around the base of the eye clearly caused blood to enter SC, which increased the optical scattering contrast in SC and allowed it to be visualized by vis-OCTA.
Conclusions :
We developed a vis-OCT microscope system to image the entire SC in vivo in mouse eyes. We demonstrated micron-level resolution and sensitivity of the system in detecting changes in SC following various perturbations of the eye.
This is a 2020 ARVO Annual Meeting abstract.