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Purpose: The purpose of this study was to assess the effects of intraoperative mitomycin-C (MMC) on the function of Baerveldt glaucoma implants in rabbits., Methods: Bilateral implantations of 200 mm2 Baerveldt drainage devices were performed in 30 normal albino rabbits. One eye, randomly selected, received intraoperative application of MMC at the site of the implant plate for 5 min, via a 6 x 4 x 2 mm cellulose sponge saturated with 0.5 mg/ml of MMC. The opposite eye served as a control. MMC-treated and control eyes (five animals each group) were compared for intraocular pressure (IOP), resistance to flow, flow rates through the implant and histopathological findings at 2, 4, 6, 12, and 24 weeks postoperatively. Resistance to flow and flow rates through the implants were studied after opening the cornea and connecting the drain tube to a micromanometric system., Results: Preoperative IOP did not differ between groups. MMC-treated eyes had lower levels of IOP than did controls at all postoperative times. The differences in IOP were statistically significant up to 8 weeks postoperatively. Resistance to flow was lower in MMC-treated eyes at all times studied, but the differences were statistically significant only at the time points of 2, 4, and 6 weeks. Flow rates through the implant bleb were always higher in MMC-treated eyes, and statistically significant differences were seen at 2, 4, 6, and 24 weeks. Histopathologically, MMC-treated eyes had thinner implant capsules with delayed maturation and less inflammatory infiltrate., Conclusion: MMC causes lower IOP and higher perfusion rates through the implant capsule at 2, 4, and 6 weeks postoperatively. Wound dehiscence, bleb leaks, and extraocular muscle injury were observed only in MMC-treated eyes. more...

Purpose: To determine pressure-flow characteristics at physiologic flow rates in vitro and in vivo in rabbits for Ahmed, Baerveldt, Krupin disk, and OptiMed glaucoma implants. The Molteno dual-chamber implant also was evaluated in vivo only., Methods: Five samples of each glaucoma implant were studied. Baerveldt implants were ligated partially for in vitro testing. Opening and closing pressures in air or after immersion in balanced salt solution or plasma were evaluated for the valved devices (Ahmed and Krupin). Pressures were measured in vitro and in vivo in normal rabbits at flow rates preset at between 2 and 25 microliters/minute after the tubes were connected to a closed manometric system. In vivo measurements were made 24 hours after implantation. Resistance to flow was calculated using Poiseuille's equation after at least three separate flow rate readings., Results: In air, the Ahmed and Krupin valves had opening pressures of 9.2 +/- 3.4 and 7.2 +/- 0.6 mmHg and closing pressures of 5.2 +/- 0.9 and 3.9 +/- 1 mmHg, respectively. Neither opening nor closing pressures could be determined when Ahmed and Krupin valves were immersed. In vitro, the Ahmed and OptiMed devices had higher pressures than did other devices at a 2-microliters/minute flow rate of balanced salt solution. During perfusion with plasma, only the OptiMed device maintained higher pressures than with balanced salt. With all devices, pressures fell rapidly to zero after flow was stopped. The OptiMed device demonstrated the highest resistance values. In vivo, the Ahmed device provided pressures of 7.5 +/- 0.8 mmHg and the OptiMed device gave pressures of 19.6 +/- 5.6 mmHg at a 2-microliters/minute flow rate. After 15 minutes of flow shutdown, the OptiMed implant maintained pressures of 7.1 +/- 1.1 mmHg. The Baerveldt (nonligatured), Krupin, and Molteno dual-chamber implants had similar resistances and pressures in vivo. Pressures with all devices in vivo fell rapidly to zero after conjunctival wound disruption., Conclusion: Neither the Ahmed nor Krupin devices had demonstrable opening or closing pressures when tested in vitro immersed in balanced salt solution or plasma. With all devices, pressures were higher in vivo than in vitro due to tissue-induced resistance around the explant. Both Ahmed and Krupin valves functioned as flow-restricting devices at the flow rates studied, but did not close after initial perfusion with fluid. more...

Background: The Krupin Eye Valve with Disk (Krupin disk) is a glaucoma shunt that incorporates a slit valve intended to minimize early postoperative hypotony., Methods: The medical records of all patients who have undergone Krupin disk implantation at the Doheny Eye Institute between July 1990 and December 1992 (25 eyes of 25 patients) were reviewed., Results: Intraocular pressure (IOP) was reduced from a mean of 36.1 +/- 11.5 mmHg to 15.3 +/- 7.5 mmHg at follow-up intervals of 4 to 19 months (mean, 13.2 months). On the first postoperative day, IOPs ranged from 0 to 40 mmHg. In two eyes (8%), the IOP was less than 6 mmHg, and in five eyes (20%) the IOP was more than 21 mmHg. Serous choroidal effusion and/or choroidal hemorrhage occurred in seven patients (28%). Six- and 12-month life-table success rates (6 < or = IOP < or = 21 mmHg) were 84% and 66%, respectively., Conclusion: The Krupin disk lowers IOP in most patients; however, the presence of a slit valve does not eliminate either early postoperative hypotony with its attendant complications or early IOP spikes. more...

Purpose: The treatment of glaucoma after scleral buckling surgery is often problematic. The authors investigated a series of patients in whom a silicone tube was implanted to shunt aqueous from the anterior segment to the fibrous capsule surrounding a previously placed silicone episcleral encircling element., Methods: Thirteen patients were retrospectively reviewed. In each patient, a silicone tube was inserted through a small incision into the fibrous capsule overlying the scleral explant. In most patients, no attempt was made to secure the distal end of the tube to the silicone band. The proximal end of the tube was inserted into the eye via a needle track., Results: Successful control of intraocular pressure (IOP) (6 mm Hg < or = final IOP or < 21 mmHg with or without medication) was ultimately achieved in 11 (85%) of 13 patients (3 of the successful patients underwent one or more surgical revisions to relieve obstruction of the proximal and/or distal tube opening). Follow-up in these patients ranged from 8 to 49 months (mean +/- standard deviation, 21.7 +/- 14.1 months). The final postoperative visual acuities were within one line of the preoperative visual acuities or had improved in 11 (85%) patients. Complications included serous choroidal detachment (3 patients; 23%), conjunctival wound leak (2 patients; 15%), hyphema (1 patient; 8%), and tube obstruction by lens, iris, vitreous, or episcleral fibrous tissue (4 patients; 31%)., Conclusion: Aqueous tube shunt to a pre-existing episcleral encircling element is useful in treating complicated glaucomas after scleral buckling surgery. Fibrous obstruction of the external tube opening is a frequent complication in the early postoperative period, but it may be relieved by surgical revision. more...

Background: The authors report four cases of conjunctival epithelial invasion into the fibrous capsule surrounding a Baerveldt glaucoma implant. All cases were associated with concurrent or recent prior scleral buckling surgery., Methods: Three patients had postoperative conjunctival wound leaks, one in the immediate postoperative period and the other two at 9 and 17 days postoperatively after release of the tube ligature. In the fourth patient, a fistulous tract developed over the implant after a first-stage insertion. Histopathologic confirmation of subconjunctival epithelialization was obtained in two of these patients., Results: Surgical revision was performed in all patients. Excision and debridement of all epithelium-lined subconjunctival tissues and extensive bipolar cautery were used in the three patients with wound leaks. Implant removal also was performed in one of these. Fistulectomy and bipolar cautery were used in the fourth patient. No recurrent wound leaks or other adverse sequelae were noted., Conclusions: Epithelial invasion of the subconjunctival space and inner bleb wall after implantation of glaucoma drainage devices can lead to breakdown of the conjunctival wound and persistent aqueous leak. Prior or concurrent scleral buckling surgery may predispose to this occurrence. Surgical revision involving epithelial debridement, cautery, and meticulous wound closure, with or without implant removal, has been used successfully in the management of this complication. more...

Two cases of pseudo-Brown's syndrome occurring after superior nasal implantation of glaucoma filtering devices are described. We hypothesize that this restriction in ocular motility was due to the mechanical effects of large filtering blebs or increased inflammation and scar formation in the superior nasal quadrant. Serial ultrasound examinations of our patients demonstrated development of a large bleb, coincidental with the disturbance in motility. Because of the risk of strabismus, we no longer recommend placing large implant devices in the superior nasal quadrant in eyes that have good vision. more...

Ninety-six patients who had undergone single-plate Molteno implantation for glaucomas with poor surgical prognoses were re-evaluated for long-term results. Control of intraocular pressure was achieved with one single-plate implant to a level less than 22 mmHg (but greater than 5 mmHg) without reoperation or devastating complications in 46% of the aphakic/pseudophakic eyes, 25% of eyes after failed filters, 25% of eyes with neovascular glaucomas, and 26% of eyes in patients younger than 13 years of age (life-table analysis at 5 years). Five-year success rates improved to 53%, 71%, 40%, and 56%, respectively, when data from second plates were included. Visual acuities improved or remained the same after one or two plates were implanted in 47% of aphakic/pseudophakic eyes, 17% of eyes after failed filters, 65% of eyes with neovascular glaucomas, and 63% of eyes in patients younger than 13 years of age on whom Snellen acuity was available. The most frequent overall complications after implantation of one or two plates included: corneal edema (19%), corneal graft decompensation (13%), and cornea-tube touch, retinal detachment, and cataract (8% each). more...