Ultrasonographic Study of Glaucoma Implant

ABSTRACT

The fibrovascular tissues surrounding a glaucoma implant have been found to play a major role for the orbital absorption of aqueous humor following a glaucoma implant surgery. An ultrasonographic study was performed to investigate the ultrasonographic, characteristics of the tissues and its relationship with the postoperative intraocular pressure(IOP) control. Twenty-three eyes of 23 patients had undergone the e-PTFE membrane-silicone tube implantation and had been followed up for at least 6-month(mean +/- SD, 17 +/- 8.8 months). An ultrasonographic study for these eyes included such paramneters as presence of an aqueous reservoir surrounding the implant, size(height) of the aqueous reservoir and echoreHectivity from the reservoir wall tissues. The aqueous reservoir was identified in 22(96%) of 23 eyes and had a height varying from 1.0 mm to 5.5 mm. In eyes with an aqueons reservoir. 3 mm high or more, the IOPs were all 21 mmHg or less without further glaucoma medications(p=0.040, chi-square). In one eye with an obliterated reservoir on ultrasonography, the opening of the silicone tube was found to be occluded toward the extrascleral portion of the implant when reoperation was performed. The echo reflections from reservoir wall tissues were denser and higher comparing with those from the sclera of the respective eye in 7 eyes with a complete failure of postoperative lOP control(>or=30 mmHg on maximum medical theraph). These eyes also had and irregular echoreflections within the aqueous reservoir, which reflect an invasion of proliferating tissues into the reservoir.