Femtosecond Laser Photodisruption on Human Trabecular Meshwork: In vitro Study

Abstract

Abstract: : Purpose: The purpose of this in vitro study was to test the ability of the femtosecond (fs) laser to create drainage canals in the human trabecular meshwork (TM), and to determine the minimum exposure time and the least amount of energy needed to create an ablation area. Methods: Corneo–scleral rims was obtained post–penetrating keratoplasty. These were cut into1 mm strips and rehydrated by immersing them in Optisol– GS. Partial thickness fistulas in the human TM were created by focusing the fs laser beam with various energies (7.2 and 14.4 µj) and at various time points (0.25, 0.5, 1, 2 sec), starting from the inner surface of the corneo–scleral rim moving towards the outer surface along the Schlemm’s canal. Specimens were stained with hematoxylin & eosin ( H&E) and imaged under a Zeiss microscope by Axioskop 2 Plus software. Also two photon images were taken. Diameters and lengths were measured with the help of image analyzer on the H&E stained sections and evaluated the collagen structure surrounding the lesion on the two photon images. Results: All selected time points and energies (except for 0.25 sec./7.2 and 14.4 µj) achieved desired photodisruption in the TM. Incisions created at 0.5 sec./ 14.4 µj applications seemed to be more ideal because they were able to achieve the full thickness trabecular ablation area consistent with clinically effective reduction in intraocular pressure. Incisions created at 1 and 2 sec./14.4 µj were deeper than those at shorter time points with the same pulse energy and wavelength. Longer exposure times and higher pulse energies were usually associated with deeper and larger incisions and minimal collateral damage. Conclusions: Our results indicate that fs photodisruption can be employed to create lesions in the human TM without damaging the surrounding tissues with appropriate exposure time and pulse energy. This demonstrates that fs laser treatments may have future potential for the surgical treatment of glaucoma

Keywords: laser • trabecular meshwork • pathology: experimental