gms | German Medical Science

102. Jahrestagung der DOG

Deutsche Ophthalmologische Gesellschaft e. V.

23. bis 26.09.2004, Berlin

Atraumatic technique of Schlemm’s channel opening and removal of juxtacanalicular and corneal trabecular layers during non-penetrating deep sclerectomy (NPDS)

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  • corresponding author A. Dashevski - Augenarztpraxis Dr. med. B. Steinmetz, Mühldorf am Inn
  • B. Steinmetz - Augenarztpraxis Dr. med. B. Steinmetz, Mühldorf am Inn

Evidenzbasierte Medizin - Anspruch und Wirklichkeit. 102. Jahrestagung der Deutschen Ophthalmologischen Gesellschaft. Berlin, 23.-26.09.2004. Düsseldorf, Köln: German Medical Science; 2004. Doc04dogDO.10.03

The electronic version of this article is the complete one and can be found online at:

Published: September 22, 2004

© 2004 Dashevski et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.



The goal of NPDS is to achieve a stable hypotensive effect while avoiding complications.

Through preparation of the internal wall of Schlemm's channel and Descemet's membrane with removal of juxtacanalicular and corneoscleral trabecular layers as well as absence of macro-and microperforations in the so-called filtering membrane are crucial for a successful application of the technique. That is why special attention should be paid to the technique of superficial and deep scleral flap fashioning and removal of juxtacanalicular and corneoscleral trabecular layers.

The superficial flap should be separated deep enough into the corneal stroma, up to 1,5 mm. Its thickness should reach 1/3 of the sclera which is approximately 270-300 microns. The flap should be elevated parallel to the surfaces of sclera and cornea. For more convenience during the following separation of the deep flap in the region of Schlemm's channel and Descemet's membrane, as well as final excision of the flap, it is suggested to design the flap in the shape of a truncated rhomb rather than an isosceles triangle or trapezium. Corneolimbal incisions are performed not at an obtuse or tight, but at an acute angle to the limbus line within the flap. Thereby, excessive tension of the tissues during separation of the deep flap from Descemet's membrane surface can be avoided. Thus the surgeon's own physical efforts are reduced. Try to perfom this manoever on a sheet of paper to understand the difference.

The deep flap is fashioned with a thickness of 2/3 of the sclera. Here attention should be paid to the following: the flap needs to be fashioned in a way that during separation of the flap towards the cornea the lumen of Schlemm's channel is entered at once. By that, the following steps will be simplified substantially. If, however, Schlemm's channel is missed because the preparation is too deep, penetration into the anterior chamber may occur or the ciliary body may be damaged. If, on the other hand, the preparation is too superficial, the corneal stroma above Schlemm's channel will be entered. As a consequence, substantial efforts will be necessary to separate the "lodged" lumen of the channel. Excessive trauma and perforation into the anterior chamber cannot be excluded. Failure to open Schlemm's channel makes the operation meaningless at all.

That is why the deep scleral flap should be separated deep enougt, but only up to a certain border. This is also necessary to create a deep intrascleral cavity which will later on serve as an important decompression reservoir between the anterior chamber with the filtering membrane and the subconjunctival filtering zone. The border should be presented by a thin, frail, semi-transparent layer of scleral fibers which should be preserved on the ciliary body surface. In order to achieve a correct orientation in the scleral layers, the sclera must be perforated at the apex of the deep scleral flap up to the ciliary body. Next, preparation must be performed moving away from the apex "flying at zero alitude" with only a thin semi-transparent scleral layers left under the knife. Following this advice you will most certainly get into the lumen of Schlemm's channel as soon as the scleral spur has been passed.

The following step is the crucial part of the whole operation: preparation of the internal wall of Schlemm's channel. The corneoscleral and juxtacanalicular trabecular layers are removed while the uveal layer is left in place. Failure to achieve this will jeopardize the success of the operation. As a rule, if the lumen of Schlemm's channel has been entered at once and the deep flap has been separated well far into the cornea, the trabecular tissue becomes visible and can easily be separated with a microsponge.

Certain difficulties may appear during removal of the two superficial terbecular layers. Usually experienced surgeons use a microforceps, but even in the hands of a surgeon advanced in NPDS perforation of uveal trabecular layer and Descement's membrane may occur. As the forceps moves from outside to inside and frome above downwards in relation to the three trabecular layers, perforation of the uveal layer cannot be excluded. On the other hand, the surgeon something fails to grasp the complete layer that needs to be removed by the forceps.

In order to remove the two superficial trabecular layers entirely and to prevent microperforation of the uveal layer and Descemet's membrane it is suggested to separate the superficial layers with a special atraumatik spatula. This spatula is inserted along the tangent to the surface of Descemet's membrane between the trabecular layers. Then the superficial layers are separated from the uveal layer with a motion from below upwards. Finally, the preparated layers are easily removed with a forceps. Any contact with the uveal layer and Descemet's membrane is avoided. The deep scleral layer is exised.

Subsequently, an implant may be inserted into the scleral cavity, depending on the surgeon's decision. If no implant is used, it is not necessary to place sutures onto the superficial scleral flap.

These additions are the result of the author's personal observations during NPDS applying to the treatment of patients with glaucoma within a period of several years.