Figure 1. Profile and scaled views of the double-plate Molteno implant (surface area, 274 mm2) (A), and the Molteno3 implant (surface area, 175 mm2) (B).
Figure 2. Scattergrams of individual intraocular pressure (IOP) results for the double-plate Molteno implant (n = 89) and the Molteno3 implant (n = 52) at 3 years. Dashed lines indicate no change between preoperative and postoperative IOP.
Figure 3. Kaplan-Meier analysis showing the probability of failure for the double-plate Molteno and Molteno3 implants.
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Thompson AM, Molteno ACB, Bevin TH, Herbison P. Otago Glaucoma Surgery Outcome Study: Comparative Results for the 175-mm2 Molteno3 and Double-Plate Molteno Implants. JAMA Ophthalmol. 2013;131(2):155–159. doi:10.1001/2013.jamaophthalmol.165
Author Affiliations: Departments of Medicine (Drs Thompson and Molteno and Ms Bevin) and Preventive and Social Medicine (Dr Herbison), Dunedin School of Medicine, University of Otago, Dunedin, New Zealand.
Objective To evaluate the efficacy of the 175-mm2 Molteno3 implant in patients with nonneovascular glaucoma.
Methods A hospital-based, retrospective historical control comparative case series comparing results in the first 87 eyes to receive the 175-mm2 Molteno3 implant with those in a control group of 115 eyes receiving the 274-mm2 double-plate Molteno implant.
Results Success was defined as an intraocular pressure (IOP) of at least 6 mm Hg but not more than 21 mm Hg with or without hypotensive medication. The mean postoperative follow-up was 3.0 years (range, 13 days to 5.6 years) in the Molteno3 implant group and 6.2 years (range, 1 day to 13.9 years) in the double-plate Molteno implant group. The mean (SD) preoperative IOP was 25.6 (7.1) mm Hg in the Molteno3 implant group in eyes treated with a mean of 2.3 ocular hypotensive medications, and 25.7 (8.0) mm Hg in the double-plate Molteno implant group in eyes treated with a mean of 2.2 medications. The mean (SD) postoperative IOP at 36 months was 13.9 (3.2) mm Hg in the Molteno3 implant group in eyes treated with a mean of 0.9 ocular hypotensive medications, and 14.5 (3.4) mm Hg in the double-plate group in eyes treated with a mean of 0.7 medications. The probability of IOP control at 3 years was 0.79 in both groups. There was significantly more postoperative hypotony in eyes without a polyglactin 910 tie in the Molteno3 implant group (P = .04); however, significantly more eyes with flat anterior chambers in the double-plate group required anterior chamber reformation (P = .03).
Conclusion The 175-mm2 Molteno3 implant provided intermediate-term successful treatment of nonneovascular glaucoma comparable to that provided by the double-plate Molteno implant.
Molteno implants (Molteno Ophthalmic) are surgical devices used to treat severe and complex cases of glaucoma.1 The indications for use have been well described,2-9 and implants are shown to offer intraocular pressure (IOP) control superior to trabeculectomy for the long term.10,11
A consistent histological pattern has been observed in bleb capsules around Molteno implants and has led the authors to hypothesize that 2 opposing processes occur, which have been described elsewhere.12-17 These observations have led to modification of the standard single- and double-plate Molteno implants (surface area, 137 and 274 mm2, respectively) in recent years, resulting in 2 single-plate Molteno3 implants (surface areas, 175 and 230 mm2) (Figure 1). Although made from the same materials, the Molteno3 implants differ from earlier models in that they have a thinner, more flexible episcleral plate, the height of the outer ridge has been reduced, and the pressure ridge outline has been modified from triangular to elliptical. The pressure ridge divides the plate's episcleral surface into small primary and large secondary drainage areas. These modifications were designed to restrict aqueous humor to the primary drainage area until apoptosis was established in the inner capsule layers, accumulating a high concentration of proapoptotic death messengers. Subsequent IOP elevation after 2 weeks to approximately 15 mm Hg lifts tissue off the pressure ridge, allowing aqueous humor to flow into the secondary drainage area, rapidly establishing the apoptotic fibrodegenerative response that ultimately results in a thinner, more permeable capsule.
We report the intermediate-term results of a retrospective historical control comparative case series including the first 87 consecutive operations to insert the 175-mm2 Molteno3 implant in patients with nonneovascular glaucoma at Dunedin Hospital.
Approval for data collection and analysis was obtained from the Lower South Regional Ethics Committee, Dunedin, New Zealand, and the study adhered to the tenets of the Declaration of Helsinki.
Both the first 87 eyes that received a 175-mm2 Molteno3 implant between April 2, 2004, and November 30, 2006, and the control group of 115 eyes that received a double-plate Molteno implant (surface area, 274 mm2) between January 1, 1995, and April 19, 2004, for any nonneovascular glaucoma at Dunedin Hospital were identified from the Otago Glaucoma Surgery Outcome Study computerized database. Complete clinical information was collected at each visit and entered in the database. Data on ethnicity were retrieved from Dunedin Hospital records. In New Zealand, ethnicity is a measure of self-perceived cultural affiliation.18
The surgical technique used for insertion of both single- and double-plate implants has been described elsewhere.19-22 The same technique was used to insert Molteno3 implants. Particular care was taken to place the anterior edge of the plate in line with the rectus muscle insertions, such that the primary drainage area was covered by the intermuscular thickening of the Tenon fascia, which was stretched slightly over the pressure ridge and sutured to sclera to form the closed primary bleb cavity. A 5-0 polyglactin 910 ligature (Vicryl; Ethicon) was used to occlude the drainage tube in eyes in which IOP could be temporarily controlled with hypotensive medication. This was combined with a Sherwood slit (a venting slit in the extrascleral part of the drainage tube)22 to provide early postoperative IOP control in cases in which a postoperative pressure spike was expected. Surgery was performed by ophthalmologists and supervised residents in training. Anesthesia was local subtenon or general.
Eyes with signs of excessive bleb fibrosis, including marked vascularity during a long period of bleb inflammation with associated IOP elevation, were given anti-inflammatory fibrosis suppression treatment.14,23
The preoperative IOP was taken as the mean IOP in the month before surgery, and the postoperative IOP was taken as the mean IOP for each postoperative month. Successful IOP control was defined as an IOP of at least 6 mm Hg but not more than 21 mm Hg with or without hypotensive medication. Failure was defined as an IOP greater than 21 mm Hg, phthisis, or reoperation. The best corrected Snellen visual acuity (BCVA) was that recorded in the month before surgery and the highest recorded each postoperative year.
A Molteno3 implant was inserted in 87 eyes of 74 patients. The mean age at operation in this group was 73.3years (range, 26-97 years), and the mean follow-up was 3.0 years (range, 13 days to 5.6 years). In the control group, a double-plate Molteno implant was inserted in 115 eyes of 100 patients; the mean age at operation was 70.0 years (range, 14-93 years), and the mean follow-up was 6.2 years (range, 1 day to 13.9 years). Patient characteristics, indication for implant insertion, previous ocular surgery, and preoperative BCVA are given in Table 1. Operative techniques, combined surgery, and use of anti-inflammatory fibrosis suppression therapy are given in Table 2.
Analyzing all cases of nonneovascular glaucoma (Table 3), we found no significant differences in IOP or hypotensive medication use between the 2 groups at any time point. Scattergrams of individual results at 3 years (n = 141) are shown in Figure 2. There were no differences in IOP or hypotensive medication use at any time point in the primary open-angle and other secondary glaucoma subgroups.
The probability of IOP control in the Molteno3 implant group was 0.85 (95% CI, 0.77-0.93) at 1 year, 0.84 (0.75-0.92) at 2 years, and 0.79 (0.69-0.88) at 3 years compared with 0.83 (0.75-0.91), 0.81 (0.73-0.89), and 0.79 (0.71-0.87), respectively, in the double-plate Molteno implant group (Figure 3).
Postoperative complications and surgical reintervention at final follow-up and BCVA at 3 years are summarized in Table 4. There were no significant differences in BCVA at 3 years.
Postoperative hypotony occurred in 31 eyes (36%) in the Molteno3 implant group and 36 (31%) in the double-plate Molteno implant group and lasted a mean of 11 (range, 4-27) and 16 (range, 1-55) days, respectively. Shallow anterior chambers resolved within a mean of 4 (range, 1-6) days in the Molteno3 implant group and 14 (range, 3-56) days in the double-plate Molteno implant group. All hyphemas resolved spontaneously and completely within a mean of 8 (range, 3-14) and 9 (range, 1-60) days, respectively. All choroidal effusions resolved spontaneously within a mean of 14 (range, 7-28) and 21 (range, 6-80) days, respectively.
In the Molteno3 implant group, there was a significantly higher incidence of hypotony and shallow or flat anterior chamber in eyes that did not have a Vicryl tie occluding the drainage tube (3 of 16) than in those that received a Vicryl tie (3 of 71) (P = .04). There were no cases of flat anterior chamber or corneal touch in this group. The double-plate Molteno implant group, however, had significantly more eyes with flat anterior chambers that required anterior chamber reformation (P = .03).
Diplopia spontaneously resolved by 4 years in the Molteno3 implant group and 1.6 years in the double-plate Molteno implant group. Other than 1 case of microvascular sixth nerve palsy in the double-plate Molteno implant group, the diplopia was limited to upgaze only, associated with bleb distension, and independent of quadrant of insertion.
This case series demonstrates the efficacy of the 175-mm2 Molteno3 implant in nonneovascular glaucoma; the IOPs achieved were comparable to those achieved up to 3 years postoperatively with the gold standard,24 the double-plate Molteno implant, in this and other studies.25-30 These results were achieved with a much smaller drainage area. We postulate that the Molteno3 implant design achieves a more favorable balance between the fibroproliferative and fibrodegenerative responses that occur in bleb capsules after implant insertion, resulting in a thinner, more permeable bleb. A recent study found that supratenon placement of a 175-mm2 Molteno3 implant achieved IOP control comparable to that attained with the original single-plate Molteno implant, presumably by avoiding the fibrotic potential of Tenon tissue.31
The single-quadrant procedure used to insert the Molteno3 implant is comparable to that required to insert other single-quadrant glaucoma drainage devices, such as the nonvalved Baerveldt implant (surface area, 250 or 350 mm2), the valved Ahmed S2 and FP7 implants (both 185 mm2), and the Krupin eye valve with disk (184 mm2). The potential benefits of single-quadrant surgery include faster, easier, and less traumatic procedures. The 175-mm2 Molteno3 implant has the smallest surface area of all available adult glaucoma drainage devices yet provides IOP control comparable to that achieved with larger devices.25-28
Significantly more eyes in the Molteno3 than in the double-plate Molteno implant group received the implant without a Vicryl tie. Eyes receiving a Molteno3 implant without a Vicryl tie had a higher likelihood of hypotony; this is not altogether unexpected, given that there is free passage of aqueous humor into the bleb cavity when no tie is used.
Visual acuities in the 2 groups were compared at 3 years rather than at final follow-up to avoid the confounding variable of different durations of follow-up. There were no significant differences in visual acuity between the 2 groups at 3 years.
In our series, patients did not necessarily undergo daily or weekly follow-up and consequently some recorded dates for resolution of postoperative hypotony may be incorrectly late. Although this possible inaccuracy is not ideal in terms of research trial methods, we believe the data provide a realistic approximation of the clinical situation.
In summary, the 175-mm2 Molteno3 implant has been found to be comparable to the double-plate implant in controlling IOP and is an effective alternative to the previous double-plate implant design.
Correspondence: Anthony C. B. Molteno, FRCS, Department of Medicine, University of Otago Dunedin School of Medicine, PO Box 913, Dunedin 9054, New Zealand (firstname.lastname@example.org).
Submitted for Publication: June 3, 2012; final revision received July 19, 2012; accepted July 24, 2012.
Conflict of Interest Disclosures: Dr Molteno declares a financial interest in Molteno implants. The other authors report having no proprietary or commercial interest in any of the materials discussed in this article.
Funding/Support: This work was supported in part by a grant from the Healthcare Otago Charitable Trust (Ms Bevin).
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