An in vitro study of femtosecond laser photodisruption in rabbit sclera

Abstract

To explore the possibility of photodisruption in rabbit sclera by femtosecond (fs) laser and seek appropriate incision techniques and relevant parameters, a fs laser (800 nm/50 fs) with different pulse energies was applied to irradiate rabbit sclera in vitro. By moving a computer-controlled three-axis translation stage to which the sample was attached, the laser achieved three types of incisions: transscleral channel, snake pattern and linear cut. The irradiated samples were observed by light microscopy and scanning electron microscopy (SEM). In comparison with fs laser, Nd:YAG was used as control. The experimental results show that through an objective lens with numerical aperture (NA) of 0.2, the fs laser with power intensity larger than 955 TW/cm² and pulse energy ranging from 37.5–125 ?J, cutting depths from 30–70 ?m may be achieved after linearly scanning in sclera at a translation speed of 0.1 mm/s. However, it failed to make any photodisruption when the power intensity was below 796 TW/cm² or the pulse energy was less than 31.25 ?J under the same condition. Compared with the Nd:YAG laser, the inner wall of the channel was smoother and the damage to the surrounding tissues was slight with the fs laser. The high precision of intrascleral photodisruption and minimal damage to surrounding tissues by a fs laser display its potential application in the treatment of glaucoma.

References

1. Toyran S, Liu Y M, Singha S, et al.. Femtosecond laser photodisruption of human trabecularmeshwork: an in vitro study. ExperimentalEye Research, 2005, 81(3): 298–305
2. Ngoi B K, Hou D X, Koh L H, et al.. Femtosecond laser for glaucoma treatment: astudy on ablation energy in pig iris. Lasersin Medical Science, 2005, 19(4): 218–222. doi:10.1007/s10103-004-0323-9
3. Juhasz T, Kastis G A, Suarez C, et al.. Time-resolved observations of shock waves andcavitation bubbles generated by femtosecond laser pulses in cornealtissue and water. Lasers in Surgery andMedicine, 1996, 19(1): 23–31. doi:10.1002/(SICI)1096-9101(1996)19:1<23::AID-LSM4>3.0.CO;2-S
4. Schwab B, Hagner D, Müller W, et al.. Bone ablation using ultrashort laser pulses.A new technique for middle ear surgery. Laryngorhinootologie, 2004, 83(4): 219–225. doi:10.1055/s-2004-814270
5. Binder P S . Flap dimensions created with the IntraLase FS laser. Journal of Cataract and Refractive Surgery, 2004, 30(1): 26–32. doi:10.1016/S0886-3350(03)00578-9
6. Lubatschowski H, Maatz G, Heisterkamp A, et al.. Application of ultra-short laser pulses forintrastromal refractive surgery. Graefe'sArchive for Clinical and Experimental Ophthalmology, 2000, 238(1): 33–39. doi:10.1007/s004170050006
7. Sacks Z S, Kurtz R M, Juhasz T, et al.. High precision subsurface photodisruption inhuman sclera. Journal of Biomedical Optics, 2002, 7(3): 442–450. doi:10.1117/1.1482381
8. Wang X F, Jia T Q, Li X X, et al.. Ablation and ultrafast dynamics of zinc selenideunder femtosecond laser irradiation. ChineseOptics Letters, 2005, 3(10): 615–617
9. Sacks Z S, Kurtz R M, Juhasz T, et al.. Subsurface photodisruption in human sclera:wavelength dependence. Ophthalmic Surgery,Lasers & Imaging, 2003, 34(2): 104–113
10. Chen H X, Jia T Q, Huang M, et al.. Visible-infrared femtosecond laser-induced opticalbreakdown of 6H SiC. Acta Optica Sinica, 2006, 26(3): 468–470 (in Chinese)
11. Niemz M H . Laser-Tissue Interactions Fundamentals and Applications (in Chinese,trans. Zhang Zhenxi). 3rd ed.Beijing: Science Press, 2005, 92–132
12. Xing Q R, Mao F L, Lang L Y, et al.. Experiment research on femtosecond laser cellmicromanipulation system. Chinese Journalof Lasers, 2004, 31(6): 728
13. Frederickson K S, White W E, Wheeland R G, et al.. Precise ablation of skin with reduced collateraldamage using the femtosecond-pulsed, terawatt titanium-sapphire laser. Archives of Dermatology, 1993, 129(8): 989–993. doi:10.1001/archderm.129.8.989
14. Suhm N, Götz M H, Fischer J P, et al.. Ablation of neural tissue by short-pulsed lasers–atechnical report. Acta Neurochirurgica, 1996, 138(3): 346–349. doi:10.1007/BF01411747
15. Krueger R R, Kuszak J, Lubatschowski H, et al.. First safety study of femtosecond laser photodisruptionin animal lenses: tissue morphology and cataractogenesis. Journal of Cataract and Refractive Surgery, 2005, 31(12): 2386–2394. doi:10.1016/j.jcrs.2005.05.034
16. Gerten G, Ripken T, Breitenfeld P, et al.. In vitro and in vivo investigations on the treatmentof presbyopia using femtosecond lasers. Ophthalmologe, 2007, 104(1): 40–46. doi:10.1007/s00347-006-1400-1
17. Serbin J, Bauer T, Fallnich C, et al.. Femtosecond lasers as novel tool in dental surgery. Applied Surface Science, 2002, 197–198: 737–740. doi:10.1016/S0169-4332(02)00402-6
18. Niemz M H, Kasenbacher A, Strassl M, et al.. Tooth ablation using a CPA-free thin disk femtosecondlaser system. Applied Physics B, 2004, 79(3): 269–271. doi:10.1007/s00340-004-1579-2
19. Vogel A, Venugopalan V . Mechanisms of pulsed laserablation of biological tissues. ChemicalReviews, 2003, 103(2): 577–644. doi:10.1021/cr010379n
20. Stern D, Schoenlein R W, Puliafito C A, et al.. Corneal ablation by nanosecond, picosecond andfemtosecond lasers at 532 and 625 nm. Archivesof Ophthalmology, 1989, 107(4): 587–592