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PubMed · 2258088

[Aqueous drainage implants in glaucoma].

Abstract

The use of implants to drain aqueous from the anterior chamber to a posterior collecting reservoir is an important additional option in the treatment of advanced refractory glaucoma. In the past decade, many problems and complications associated with drainage implants have been solved by modifications in implant design and surgical technique. These include: entry of the tube into an equatorial collecting device, increased surface area of the collecting reservoir, use of a needle track to insert the tube into the anterior chamber, suturing a donor scleral patch to cover the tube, intracameral injection of hyaluronic acid (Healon), ligation of the tube with a temporary suture, and antifibrotic medical therapy. The adoption of some or all of these modifications in recent years has clearly resulted in fewer complications and better long-term control of intraocular pressure.

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BibTeXRIS

I Ashkenazi, S Melamed, M Blumenthal. 1990. [Aqueous drainage implants in glaucoma].. https://pubmed.ncbi.nlm.nih.gov/2258088/

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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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