Abstract

SO.14.01

Pathophysiology of new glaucoma operations

Franz Grehn
Universitäts-Augenklinik Würzburg

The increase of outflow resistance is the cause of elevated intraocular pressure in glaucoma. In primary open angle glaucoma, the larger part of outflow resistance is located in the trabecular meshwork. Therefore surgical methods have been developed which decrease the resistance of the trabecular meshwork (I-stent, trabectome, trabeculotomy). Other surgical procedures preserve the corneoscleral meshwork but remove the cribriform layer where most of the resistance is located (deep sclerectomy and other non-penetrating procedures). However, an important part of the resistance is probably located beyond the trabecular meshwork. This applies to Schlemm´s canal collapse in primary open angle glaucoma over some part of the circumference as well as to the resistance of the collector channels and the scleral venes. These resistances can be addressed by viscocanalostomy (increasing the width of Schlemm´s canal and collector channels) and by viscocanalosplasty (increasing the width of Schlemm´s canal and the tension of the trabecular meshwork by using a suture).
Filtration surgery is the only procedure that removes all resistances between anterior chamber and the sclera and conjunctiva. All other operations remove only parts of the resistance. This may explain why IOP reduction is less pronounced in non-penetrating procedures without filtration as compared to trabeculectomy, but the complication rate seems more favourable in non penetrating surgery.

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