University of Heidelberg Department of Ophthalmology

1. Fig.1: Gas chromatographic Scan of non laser treated human nucleus Fig. 2: Gas chromatographic Scan of laser treated human nucleus Fig.3: Table of mass spectrograph scan of untreated nucleus) Fig.4: Er:YAG cataract laser (Cut 2940, InPro)) Fig.5: Table of mass spectrograph scan of laser treated nucleus) Fig. 6: Scan of reference untreated fragments(1A_3D.D) Fig. 7: Scan of treated fragments (1A.D) Acknowledgements: Supported by the Bio Chemical Institute of the University of Heidelberg We thank Dr. U. Gehm of InPro GmbH, Hamburg for providing a laboratory modelof a Er:YAG cataract laser CUT 2940 Fig. 8: Scan of treated reference one day after (1A_4.D) Toxicological Study of Laser-Induced Pyrolysis Products in Cataract Surgery Specht H, Auffarth GU, Burk ROW, Voelcker HE Introduction Phacoemulsification is the standard in cataract surgery. Ultrasonic phacoemulsification is highly effective and today standardizied. Concerns exist about the potential risks of ultrasonic energy delivered by the phacoemulsification tip on such nontarget ocular structures a s the corneal endothelium [2]. Laser assisted cataractous lens removal has been investigated because of ergonomic considerations and the desire to minimize surgical invasiveness [5]. Several laser technologies from the wavelength of UV to IR have been investigated there for. Different methods of nucleus cracking are capable mostly used is the Er:YAG laser in directly contact mode [4]. In contrast to a standard phaco procedure only small openings within the corneal tissue are aimed for. The purpose of this in vitro study is to evaluate the feasibility of toxicological risks [1] of the pyrolysis products [3] created by Er:YAG laser Treatment of lens fragment (assembled from clinical cataract patients). Purpose To estimate the possibility of toxically pyrolysis products after laser treated cataractous nucleus under surgical conditions. Materials and Methods Photoablation: Used was a Er:YAG laser (Fig.4: InPro Hamburg, Germany; Type CUT 2940) in the normal spiking mode. The Er:YAG emits a radiation of 2.94 µm with a tuneable pulse lengths < 600 µs and a repetition rate < 10 Hz up to a maximal averaged power of 10 W. The laser was operated multimode with a uniform beam profile. At the tip, the laser beam was coupled into a zirconium fluoride fiber of 600 microns core diameter. The tip was used in contact mode to fracture and emulsify the nucleus. The energy per pulse delivered through the fiber was measured with a joule meter (PEM 10) at its high sensitivity of 81.5V/J. The fluence per pulse was calculated from energy per pulse and the measured spot diameter. The fluence was regulated by changing of the bank voltage. Parameters were: energy of35 mJ, repetition rate of 3 Hz and a puls length of 250 µs. The lens fragments from 3 patients were used according to conventional method. The fragments of the lenses as well as the BSS liquid with rests of Healon GV were caught in a bag after ultrasound phaco. The samples were divided in each case in equal parts and a proportion was treated once with the Er:YAG laser. The untreated sample served as reference. Analysis: The analysis of the burn-up products was executed at a gas chromatograph and mass spectrograph. For this first screening a non polar column was used. Results Thisfirst screening points showeda modification of thedetermined data from untreated material (Fig.1) to treatedmaterial (Fig.2). This modification could be observed in each case with the samples of the 3 patients. The data of the laser treated sample showed additional various, different masses could be detected. These mass numbers (Fig.3,5) are representing substances in the samples were detected. The measurements of the treated samples showed the same spectral mass again almost on the following day as the untreated samples (Fig.6-8). Conclusion The results of this investigation do not permit a conclusion over poisonous of the detected substances especially not an clinical reaction. The measurements with polar columns necessarily enable a very narrow-band detection of individual chemical products. The investigation allows the statement that the detected substances are short-lived or volatile. A precise investigation of the detected substances is necessary to exclude the toxicologically potential of these laser induced products. University of Heidelberg Department of Ophthalmology INF 400, D-69120 Heidelberg; Germany E-mail:Holger_Specht@med.uni-Heidelberg.de ASCRS American Sociaty of Cataract and Refractive Surgery 2001 • Literature: • Albrecht HJ, Wäsche W, Müller GJ. Assessment of the risk potential of pyrolysis products in plume produced during laser treatment under OR conditions. Proc. SPIE 2323; 1994: 455-463 • Berger JW, Talamo JH, et. al. Temperature measurements during phacoemulsification and erbium:YAG laser phacoablation in model systems. J Cataract Refract Surg 1996 Oct; 22(8): 1003 • Bindig U, Wäsche W. Analyse von Abbrandprodukten beim Einsatz medizinischer Laser. Berlien, Müller – Angewandte Lasermedizin – 13.Erg. Lfg. 10/97 • Dodick JM. Laser phacolysis of human cataractous lens. Dev Ophthalmol 1991; 22: 58-64 • Eichenbaum D. Phaco is easier to do with the new laser system. Ophthalmology Times 1994; 19(13)