Purpose:
To study the feasibility of using a two-photon-ophthalmoscope for imaging of Schlemm’s canal endothelium cells and selective laser trabeculoplasty surgery.
Methods:
In this experimental study on freshly obtained pig eyes, we used a nonlinear scanning laser ophthalmoscope (SLO) which included a two-photon excited fluorescence/second harmonic generation imaging modality (laser duration: 150 femtoseconds; 810 nm wavelength; power 120 mW). Applying this laser ophthalmoscope, we imaged the trabecular meshwork on flat mounts. Before, we had used the same laser (laser duration of 1µs, 810 nm wavelength, laser power of 325mW) to create laser burns in the trabecular meshwork similar to the conditions of selective laser trabeculoplasty. With the three-dimensional (3D) imaging method of the laser ophthalmoscope, we assessed the ultrastructure of the trabecular meshwork and assessed the feasibility of using an acoustic modulator to target specific cells within the trabecular meshwork. We obtained multiple two-photon images to analyze the relationship between the dehydration level of the tissue and the laser power of the burning point.
Results:
Using the setting of a selective laser trabeculoplasty and applying the fine-tuning of the laser power, we were able to create small laser burns inside the wall of trabecular meshwork in a depth of 20µm. These laser burns were imaged by the same laser using the imaging conditions as described above. We also observed signs of vaporization in the wall of the Schlemm's canal.
Conclusions:
Two-photon imaging of the trabecular meshwork with high resolution three-dimensional structural images at a low laser power of 120mW was able to visualize laser burns in the depth of the trabecular meshwork and laser effects in the wall of Schlemm's canal, which were obtained by the same laser using the physical conditions of a selective laser trabeculoplasty. Two-photon imaging allowed the visualization of deep structures of the trabecular meshwork which are usually not easily assessable for examination. As a new technique, two-photon imaging may have the potential for evaluating the structure, and potentially function related structural changes, in the trabecular meshwork. It may include aqueous outflow.
Keywords: trabecular meshwork • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • microscopy: light/fluorescence/immunohistochemistry