The Fundamental Research Of The Application Of Nanojoule Energy Pulses By Femtosecond Fiber Laser On Sclerectomy

Objective:The in vitro study is to evaluate whether nanojoule femtosecond pulses (NFP) can make ablation on sclera and investigate the effect on sclera modification.Background:Glaucoma has been the leading cause of irreversible blindness in the world. Ant i-glaucoma surger ies face difficulties in ensuring long-term surgical effectiveness resulting from fibrosis of incisions. Reduced damage of tissue during operation can validly limit fibrosis after filtering surgery. NFP provides usaprom ising way to prevent fibrosis by creating extremely precise and smooth incisions with little collateral damage.Methods:Incisions on in vitro rabbit sclera were created by NFP with repetition rate in MHz range. A computer controlled three dimensional scanner system was used to administrate diverse patterns of scan. The observation of modification and the temperature distribution of the sclera surface was realized by a charge coupled device (CCD) and a thermal infrared imager respectively. Morphological changes of each sample were observed by scanning electron microscopy (SEM), HE and Masson staining. Results:Transscleral channel, cuboid ablation, siit-like and subsurface incisions were accomplished by four patterns of scanning. The depths of one-time linear lesions induced by NFP increased with rising exposure time and decreasing focus depth. Cross section observation of treated sclera examined by SEM showed that inner wall of incision was extremly smooth (Ra=0.93±0.14 ?m). Real-time observation of the temperature distribution showed that NFP could produce thermal effect on the sc I era, which is in positive relation with exposure time and pulse energy. In addition, HE and Masson staining showed that heat accumulation could indeed produce thermal effect on the collateral tissue.The comparison between NFP and microjoule femtosecond pulses(MFP)revealed that inner surface roughness of NFP-made incision decreases significantly (P=0.0135) in comparison to the one with MFP-made incisionConelutions:Our results illustrate the potential use of NFP in minimally invasive laser sclerostomy for glaucoma therapy. It is the first example of sclera ablation with NFP to our knowledge. The thermal effect of collateral tissue produced by NFP, which was little, occurred during the process of mircofibrication. Subsurface ablation of hydrated sclera is accomplished by NFP at 1040 nm. In comparison to microjoule femtosecond pulses (MFP), NFP can make extremely precise incisions with smoother inner wall. NFP may realize the goal of successfully anticipating in anti-glaucoma filtration surgery...