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Editors Selection IGR 17-4
Intraoperative Evidence of Outflow
Comment by Murray Johnstone on:
52019 Episcleral Venous Fluid Wave: Intraoperative Evidence for Patency of the Conventional Outflow System, Fellman RL; Grover DS, Journal of Glaucoma, 2014; 23: 347-350
Fellman and Grover report the results of an observational case series. The series provides evidence that following trabectome surgery an aqueous fluid wave is elicited in the episcleral veins by using the infusion port to induce a pressure rise during phacoemulsification. The authors conclude that the aqueous fluid wave signifies patency of the outflow system distal to the Schlemm's canal, further suggesting the fluid wave provides a prognostic indicator for successful surgery.
Currently, there are no reliable prognostic indicators for the success of minimally invasive glaucoma surgery (MIGS). These author's careful clinical observations have led to the proposal of a new tool to explore the effects of such procedures. Extension of their intraoperative observations to long-term follow-up in a larger series of patients could determine whether the technique in fact has prognostic value.
There are no reliable prognostic indicators for the success of minimally invasive glaucoma surgery
In addition to intraoperative evaluation of outflow system function and surgical outcomes assessed by long-term pressure control, it would be of considerable interest to continue to monitor flow in the aqueous and episcleral veins postoperatively. Correlations could be made between such aqueous vein flow and gonioscopic evidence of cleft closure or postoperative pressure elevation.
Ideally, prognostic tools would be office, rather than operating room based, selectively eliminating poor surgical candidates before going to the OR. For example, office gonioscopy with large or flanged goniolenses can raise local episcleral venous pressure. Rapidity and completeness of blood reflux into Schlemm's canal provides evidence of the patency of the distal outflow system. Aqueous vein presence, pulsatility and the aqueous influx phenomenon with episcleral vein compression offer additional office-based prognostic tools. The authors' findings represent a valuable clinical contribution, particularly because they raise the possibility of a renaissance in the use of long-forgotten prognostic tools that rely on the art of direct clinical observation of outflow system behavior.
References
- Ascher KW. Backflow Phenomena in aqueous veins of normal and of glaucomatous eyes. Am J Ophthalmol 1944; 27: 1074-1089.
- Ascher KW. Glaucoma and the aqueous veins. Am J Ophthalmol 1942; 25: 1309-1315.
- Ascher KW. Aqueous veins and their significance for pathogenesis of glaucoma. Arch Ophthalmol 1949; 42: 66-76.
- Ascher KW. The aqueous veins. Springfield: Charles C. Thomas, 1961.
- Thomassen TL. The glass-rod test in glaucomatous eyes. Br J Ophthalmol 1949; 35:773.
- Kleinert H. The compensation maximum: a new glaucoma sign in aqueous veins. Arch Ophthalmol 1951; 46:618.
- Kronfeld PC. Further gonioscopic studies on the canal of Schlemm. AMA Arch Ophthalmol 1949; 1: 393.
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