Subsurface Photodisruption for Potential Noninvasive Glaucoma Surgery

Abstract

Abstract: : Purpose: Conventional glaucoma surgical procedures stimulate a healing response which is often accelerated by the trauma inflicted on the conjunctiva and episclera at the incision site and results in scarring and subsequent closure of the passage. We propose to test the ability of ultrashort pulses to make subsurface incisions in human sclera. By employing femtosecond photodisruption with appropriate wavelengths, laser light can be focused in the translucent sclera without the use of dehydrating agents and subsurface ablation can be achieved with minimal collateral damage while leaving the overlying tissues intact. This might defer or avoid the healing response associated with the trauma that the conjunctiva and episclera experience with conventional surgical procedures. Methods: Femtosecond pulses with various energies at wavelengths in the transmission windows of the scleral axial transmission spectrum were used to ablate human scleral tissue in vitro. The laser focal spot was scanned from the cornea to the sclera in a deep to superficial manner. Histological results were then compared using light microscopy. Results: All three selected wavelengths (1.3 µm, 1.7 µm, and 2.2 µm) achieved subsurface photodisruption in the sclera without damaging the overlying tissues. The achieved incision depth varied from specimen to specimen and from location to location on the same specimen due to tissue inhomogeneities. Incisions created at 1.7 µm seemed to be deeper than those at 1.3 µm and 2.2 µm with the same pulse energy, but the difference was small. Greater pulse energies usually were associated with deeper incisions and somewhat larger collateral damage. Conclusions: Through the use of appropriate wavelengths, our results indicate that photodisruption can be employed to create subsurface incisions in the translucent sclera without damaging the overlying tissues. This technique offers potential for noninvasive laser treatment of glaucoma.

Keywords: laser • sclera • wound healing