knot. Premature loss of silicone stents may also occur from the knot becoming loose.

3.4Dacryoendoscopy with Transcanalicular Laserdacryoplasty (TLDP)

In principle, transcanalicular endoscopy with ultraÞne endoscopes is no more invasive than a deep probing of the lacrimal system. Endoscopy is mostly carried out before any surgical procedure, whether conventional or endoscopic, which is usually performed with the patient under general anaesthesia.

The puncta have to be dilated. Irrigating softly, the endoscope is inserted via the upper or lower canaliculus. As in normal lacrimal systems the endoscope is pushed forward as far as possible down to the inferior meatus, in other cases up to the point of stenosis. The complete lacrimal passage can be judged by retracting the endoscope with simultaneous irrigation.

In children under the age of 2 years, the small diameter of the lacrimal system, especially of the punctum, increases the risk of injury. Therefore a purely diagnostic endoscopy should only be carried out in exceptional cases.

In normal Þndings [23], the canalicular mucosa appears white and smooth. The canaliculi have a narrow lumen and a homogeneous structure of the walls. The mucosa of the lacrimal sac is reddish, the lumen is wide and the wall is structured by ßat valves. The lumen in the nasolacrimal duct is narrow and shows no valves. The structure of the surface is reddish as in the lacrimal sac. The nasal cavity is noticeable as an intensely red structure with a smooth surface and an enormous space. Membrane surface scars, submucosal scar formations and foreign bodies can be compared with normal Þndings.

There is no special care after a diagnostic dacryoendoscopy.

Complications may be as follows

¥Edema or haematoma of the eye lid because of a via falsa occurs in approximately 2%.

¥Slitting of the lacrimal punctum or spontaneous dislocation of the silicone intubation (e.g. by blowing the nose) occurs in less than 5%.

First attempts to rechannel a closed lacrimal system by laser have been reported using a Holmium-YAG

laser [19]. The term ÒcanaliculoplastyÓ was used for this procedure. After the introduction of transcanalicular endoscopes [39], rechannelising of the lacrimal system was possible under endoscopic control and the term ÒlaserdacryoplastyÓ is used for this procedure [21, 53].

With regard to the diameter of the laser Þbre, endoscopically controlled rechanneling by a laser system is possible.

Using a modiÞed miniaturised Erbium-YAG laser developed for glaucoma surgery, a 375-mm sapphire Þbre delivers the laser energy at the top of the probe up to a maximum of 50 mJ and a frequency of 1Ð3 Hz.

The length of the used laser Þbre is 10Ð11 cm. The Erbium-YAG laser has a wavelength of 2.94 mm, a wavelength at which the maximum absorption is in water and the laser is operating photoablatively. The mucosal cells of the lacrimal sac have a water content of 80%, so the laser effect can be seen quickly.

The main effect of this laser in the lacrimal passage closed by the stenosis, however, is the resulting cavitation blister and not the ablation [58]. The preparation of bone holes is not possible with the Erbium-YAG laser.

The cavitation blister, which is caused by the laser impulse in the closed system, can extend over several millimetres. Punctal membranous stenosis can be opened by several impulses. The depth of penetration of the laser energy is only a few micrometers and the thermal effect is low.

The necrosis zone is only 10Ð20 mm and there is no carbonisation. A modiÞcation of the JŸnemann probe from two to three working channels allows placement of the laser Þbre into the third channel and enables the laser treatment of the stenosis to be performed under endoscopic control. An additional short laser tip with a length of 4 cm has been used for the treatment of canalicular stenosis; this tip is not integrated in an endoscope. The endoscopic examination has to be performed before the laser application.

3.4.1 Indication for TLDP

A laserdacryoplasty is possible in cases of canalicular stenosis and high or deep intrasaccal lesions. The known anatomical valves seem to be the predilection points for adhesion of the valves, causing the closure