Laser dacryoplasty is not useful in cases of acute dacryocystitis, mucoceles, or widespread adhesions following viral infections such as herpes or lacrimal stenosis caused by bone displacement after midface fractures.

A modified miniaturized Erbium-YAG laser developed for glaucoma surgery has been in use since 1996 and delivers the laser energy by a sapphire fiber. In different parts the laser energy depends on the width of the laser fiber and with the used sapphire fiber of 375 mm an energy of 50 mJ with 1-3 Hz can be delivered at the top of the fiber. The absorption maximum of the Erbium-YAG laser is in water and the laser works photoablatively. The mucosal cells of the transitional epithelium of the lacrimal sac have a water content of nearly 80%, so the ablation results quickly. But there is not only the ablative effect: depending on the complete closure of the lacrimal system after the introduction of the endoscopic probe, a cavitation blister results of energy laser impulse and the edges of membranes and valves, which stick together, can be opened by the laser effect. The blister can extend over several millimeters and in this way punctal membranous stenosis can be opened with just a few pulses. In many cases this energy is powerful enough to open these membranous stenoses, but not too strong to make a false passage.

Initially, a diagnostic endoscopy is performed to check the indication for surgery. With complete stenosis of the lacrimal system without a mucocele there is an indication for LDP. The laser fiber is brought into an endoscope with a third working channel and the laser can be applied. After several laser impulses, free irrigation can be noted. Irrigation is now possible without the former resistance and the endoscopic picture confirms the opening. After opening the obstruction, bicanalicular intubation using a silicone tube with a diameter of 0.64 mm is carried out to prevent postoperative adhesions of the mucosa. The tubing remains in place usually for 3 months and is removed transcanalicularly (Fig. 10.7).

If there is no possibility of bicanalicular intubation, then a monocanalicular stent is used according to Fayet et al. [23]. This Monoka intubation remains

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Essentials of Human Physiology

Essentials of Human Physiology

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