Ophthalmic surgeries on post mortem porcine eyes with picosecond ultrashort laser pulses.

Purpose: This work demonstrates significant advantages in ophthalmic surgeries through the use of picosecond ultrashort laser pulses instead of state-of-the-art nanosecond laser pulses. These ultrashort lasers shall serve as universal tools more effectively combining advantages of high precision, low impact and economic advantages compared to existing instruments. Methods: As samples, we used post-mortem porcine eyes on which we performed the experiments with both picosecond and nanosecond lasers. Performed surgeries were laser iridotomy, (post-) cataract treatment/capsulotomy and selective laser-trabeculoplasty. Pulse widths were between 12 ps and 220 ns with pulse energies between 30 µJ and 10 mJ at 532 nm and 1,064 nm. Additionally, we investigated accompanying shock waves, cavitation bubbles, and heat effects during the ablation processes. Results: For all surgeries, significant differences were observed between picosecond and nanosecond pulses: It was possible to scale the pulse energy down to 10 of microjoules rather than requiring millijoules, and resulting tissue ablations are much more precise, more deterministic and less frayed. The shock wave and cavitation bubble investigation revealed major differences in pressure between picosecond pulses (0.25 MPa, 50 µJ) and nanosecond pulses (37 MPa, 5 mJ). The heat input during ablation could be lowered by two orders of magnitude. Conclusion: Picosecond ultrashort laser pulses show substantial benefits for several ophthalmic surgeries, with regard to ablation precision, shock wave generation and heat input. They are better than state-of-the-art ophthalmic nanosecond lasers in all aspects tested.

Improved ex vivo training model for percutaneous renal surgery.

Percutaneous endourological procedures require an advanced level of skills. To facilitate the training of the proper technique, some years ago we developed a porcine ex vivo model for training percutaneous endourological procedures. When dilating the percutaneous tract silicone and gelatine were frequently damaged thus inhibiting proper working with the endoscopes. To circumvent these problems we improved our ex vivo model in order to be as close to the clinical situation as possible. The kidney with the ureter was dissected off the retroperitoneal organ package of the freshly slaughtered pigs. The kidneys were put into bags cut into parts of the thoracic/abdominal wall of these pigs. The renal pelvis can be filled with saline to simulate hydronephrosis; stones can be implanted for PCNL. Our new model allows for even better training of all percutaneous endourological procedures (e.g. percutaneous nephrostomy, PCNL, endopyelotomy). Especially puncturing is extremely close to the situation in humans as the porcine thoracic/abdominal wall in principal has the same anatomy as the human one. The new model has been already used with great success in hands-on courses. Concerning "tissue feeling", the anatomic relations and the great variety of procedures that can be trained, it is superior to non-biological models. Nevertheless, it is easily available and inexpensive.

Ex vivo training model for percutaneous renal surgery.

Percutaneous endourological procedures require an advanced level of skills. To facilitate training in the proper technique, simulators are helpful. Non-biological models, useful for learning the basic steps, do not represent the clinical situation in an ideal way. Recently, we developed a porcine urinary tract model for ureteroscopy. Proceeding from this experience, we developed a further ex vivo model for training percutaneous endourological procedures. The kidney with the ureter is dissected off of the retroperitoneal organ package of freshly slaughtered pigs. It is embedded in silicon. The renal pelvis can be filled with saline to simulate hydronephrosis, stones can be implanted for percutaneous nephrolithotomy. This ex vivo model allows training of all percutaneous endourological procedures (e.g. percutaneous nephrostomy, percutaneous lithotomy, endopyelotomy). It is an ideal way to train these techniques, being superior to non-biological models in terms of "tissue feeling" for anatomic relations, and the great variety of procedures that can be trained. Nevertheless, it is readily available and inexpensive.