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This study is a 10-year consecutive case series of 34 patients with insertion of graft-free Molteno glaucoma drainage devices (GDDs) using our previously described technique.1 No grafts were used over this period on any patient having Molteno GDD insertion. Following quadrant conjunctival peritomy, a bent microvitreoretinal blade is guided through a small partial-thickness scleral incision 5–6 mm from the limbus, thence through the superficial scleral lamellae into the anterior chamber, creating a tunnel for the tube following removal of the blade, obviating the need for an overlying graft and thus eliminating the risk of variant Creutzfeldt–Jacob disease (vCJD) transmission. Although there are no reported cases of vCJD from donated eye tissue, its incubation period is unknown, and vCJD is thought to be a greater transmission threat than other prion diseases, as it is more resistant to conventional sterilisation and more widely distributed in body tissues.2 This study was approved by the relevant ethics committees.
Complete success was defined as a postoperative intraocular pressure (IOP) between 6 mm Hg and 21 mm Hg. Qualified success was defined as an IOP between 6 mm Hg and 21 mm Hg using antiglaucoma medications. Figure 1 shows Kaplan–Meier survival curves for the probability of successful IOP control. Complete success rates were 45% at 1 year, 40% at 2 years and 32% at 5 years. Qualified success rates at 1, 2 and 5 years were 70%, 60% and 54%. At 10 years, the complete and qualified success rates were 15% and 40%. IOP decreased from a preoperative mean (SD) of 41.2 (13.0) mm Hg to 13.75 mm Hg at the end of the postoperative follow-up period. The generalised estimating equations (GEE) analysis shows an average reduction from baseline and postoperative IOP (over the initial follow-up period) of 23.5 mm Hg (95% CI 19.4 to 27.5 mm Hg, p=0.01). There were no intraoperative complications, and no complications related to the absence of a graft. In the first postoperative month, complications included two cases of flat anterior chamber (AC), two cases of hyphaema and one case of hypotony requiring reformation of the AC and tying off the tube. Longer-term complications included corneal decompensation, four cases requiring penetrating keratoplasty. No cases of corneal endothelium-tube touch were noted. Erosion of the conjunctiva over the plate occurred in one patient 1 year postoperatively. There was no erosion of the conjunctiva overlying the tube, or tube migration in any patient.
Criticism has been made of our technique by Molteno due to the corneal decompensation rate.3 Other studies report corneal decompensation rates ranging from 1.5% to 20%. Examination of these studies reveals a heterogenous population of patients having GDD insertion for a variety of diagnoses, utilising a variety of techniques (scleral flaps, scleral grafts, with or without combined cataract extraction) and it is not clear in some of these studies whether patients with corneal decompensation prior to GDD insertion (eg, pseudophakic bullous keratopathy) were included.4 5 Another study included only those corneas requiring penetrating keratoplasty, which may have led to under-reporting of corneal decompensation rates.6 In our study, if only corneas requiring penetrating keratoplasty were included in rates of postoperative corneal decompensation, the rate would have been 11.7%. Further studies are required to adequately compare corneal decompensation rates between our surgical technique and others, including Molteno's scleral flap technique.
This study is a consecutive case series of an alternative surgical technique for the insertion of Molteno GDDs. Long-term follow-up shows that this technique is not associated with additional complications, and the GDD continues to provide equivalent IOP control in the first 10 postoperative years in comparison with other series in the literature. This technique also has the advantage of eliminating the need for a donor scleral graft, thus eliminating the potential risk of prion transmission.
Competing interests None.
Ethics approval Ethics approval was provided by the Sydney South West Area Health Service.
Provenance and peer review Not commissioned; externally peer reviewed.
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