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Brett King, Thomas Gast, Kaitlyn Sapoznik, Ting Luo, Stephen A Burns; Adaptive optics scanning laser ophthalmoscopy of the human iridocorneal angle in vivo. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4642. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To use an altered adaptive optics scanning laser ophthalmoscope to have cellular level in vivo imaging of the iridocorneal angle and perform a preliminary study of the anatomy in normal control subjects. Glaucoma is a leading cause of irreversible blindness with increased intraocular pressure (IOP) as a leading risk factor for development and progression. IOP is mainly regulated by outflow of aqueous humor through the iridocorneal angle including the trabecular meshwork (TM) and Schlemm's canal yet in vivo visualization of these structures has relatively poor resolution. Improved imaging is therefore warranted.
A customized gonioscopy lens and holder was added to the Indiana University Adaptive Optics Scanning Laser Ophthalmoscope. The right eye of 6 healthy, control subjects ages 29 to 67 were enrolled after informed consent. Topical anesthesia was applied and subjects were advanced into the AOSLO and goniolens using a motorized positioner and under video monitoring. Video sequences were gathered of the inferior iridocorneal angle at 30 Hz. The images were processed with a custom Matlab program with an enhanced contrast algorithm. TM cell and beam size were measured in Adobe Photoshop CS6.
The iridocorneal angle was imaged in all six subjects (Figure 1), with visualization of the corneal collagen bundles, corneal-trabeculae meshwork, uveal meshwork (UM), and iris (Figures 1 & 2). Beams of the UM and TM sizes varied between subjects ranging from 28-55 µm (average 38 µm) while the UM beams were coarser ranging from 56-204µm (average110 µm). The mesothelial cells of the UM were measured to range from 13-37 µm (average 21 µm). Also visible were the lamella of the peripheral cornea measured to be 56-98 µm (average 73 µm).
Preliminary studies support the ability of the AOSLO to image details of the trabecular meshwork at high resolution. These images are comparable to images obtained with scanning electron microscopy of pathology specimens. Continued development of this technology could provide further insight into inter-subject variability of the TM as well as response to pharmacological and surgical alterations to outflow of aqueous humor in people with glaucoma.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Figure 1: AOSLO image of the human iridocorneal angle. The iris is in the lower right corner and the cornea is in the upper left corner with the TM between.
Figure 2: Image of the uveal meshwork beams lined with cells.
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