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PubMed · 523069

Shell tamponade in filtering surgery for glaucoma.

Abstract

The glaucoma shell tamponade technique in filtering surgery for glaucoma is a technique for (1) decreasing the incidence of flat anterior chamber and choroidal separation postoperatively, (2) promoting the development of a low diffuse filtration area, and (3) increasing the possibility of achieving very low resulting postoperative pressure. The glaucoma shell technique is applicable to all types of filtration procedures, including conventional filtering procedures utilizing no scleral flap and those utilizing a scleral flap, such as trabeculectomy. It can be used at surgery or can be applied in the postoperative period to deal with flat or shallow anterior chambers immediately at the time of onset. The shell tamponade technique can be utilized to aid in the management of some cases of leaking bleb in the early postoperative period or in the late postoperative period. The technique for operative and postoperative use of the glaucoma shell tamponade technique and its closely related pressure dressing is a demanding and exacting art. Because the technique increases the possibility of very low resulting tensions, its use should be considered especially for cases in which very low pressures are desired, such as some cases of extremely advanced cupping and field loss and low-tension glaucoma.

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BibTeXRIS

R J Simmons, R L Kimbrough. 1979. Shell tamponade in filtering surgery for glaucoma.. https://pubmed.ncbi.nlm.nih.gov/523069/

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Model of pulsatile-flow of aqueous humor through the iris-lens canal.

PURPOSE: To present a model of pulsatile-flow of aqueous humor from posterior (PC) to anterior chamber (AC) and to analyze the sensitivity of this novel model in detecting typical high risk conditions predisposing to pupillary block. METHODS: The model assumes noncontinuous flow of aqueous through the iris-lens canal. Aqueous that fills the canal will be ejected toward the AC-side of the canal at certain time intervals, and between 2 events of aqueous ejection there is no actual flow through this canal. Pupillary pumping rate (PPR) was calculated from the aqueous flow rate and the calculated volume of iris-lens canal. RESULTS: PPR values were generated by incorporating pupillary diameter (1 to 8 mm), aqueous flow rate (1 to 2.5 microL/min), and iris-lens canal width (0.5 to 2 mm) and height (3-9 microm) in numerical experimentation with the present model. PPR showed inverse dependence on iris-lens canal height and pupillary diameter and was directly proportional to aqueous flow rate, in agreement with the steady-flow model. However, contrary to the steady-flow model, PPR showed inverse dependence on iris-lens canal width and predicted the anticipated PC-AC pressure gradient changes at simulated light-dark transition in eyes of patients with clinically narrow angles and ultrasound biomicroscopy evidenced pupillary block. CONCLUSIONS: Upon the incorporation of real ultrasound biomicroscopy measurements in numerical experimentations with both models, the present pulsatile-flow model, contrary to the steady-flow model, showed good predictability of PC-AC pressure gradient changes in a typical condition predisposing to pupillary block.

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