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Possible outflow mechanisms for deep sclerectomieK. E. Kotliar, M. Mertz, I. M. Lanzl
Introduction: The positive results of treatment of abnormalities of aqueous outflow with the help of deep sclerectomy as well as some other surgeries (for example the Viscocanalostomy) need theoretical explanation. Such theoretical explanation would lead to better understanding of the clinical data. Some recomendations may be than given in order to improve surgical treatment. The worked out earlier mathematical and biomechanical model of the aqueous drainage system helped us to calculate the probable amount of aqueous, which flows through the possible postoperative pathways.
Methods: A biomechanical model was developed to calculate and evaluate possible outflow properties in the postoperative situation.
Results: In our model six possible drainage pathways are evaluated for the produced aqueous (~2.2mm3/min) after the deep sclerectomie: 1) via Schlemm's canal in the most favourable instances (<0.42mm3/min, and in case of viscoelasticum in the clearance of the canal, if the radius of this hindrance is two times smaller than the radius of the clearance: <0.06mm3/min); 2) through the uveoscleral outflow (~0.18mm3/min); 3) through the roof of the newly created flap per diffusionem (~0.03mm3/min); 4) unintended leakage may occur under the conjunctiva; 5) residual drainage through the trabecular meshwork into the Schlemm's canal. 6) through the cutting open of collector channels in the roof of the newly created scleral lake (~0.91mm3/min).
Discussion: According to our calculations the main amount of the aqueous after the operation could not flow only through the operative open ends of
Schlemms canal and further in the episcleral veins. The major pathway seems to be through shortened collector channels in the scleral roof of the newly created intrascleral reservoir. This should be considered in the future changes in surgery techniques.
Ophthalmological hospital, Klinikum rechts der Isar, Technical University of Munich, Ismaningerstr., 22, D-81675 Munich