Year : 1994 | Volume
: 42 | Issue : 4 | Page : 193--197
Single-plate Molteno implants in complicated glaucomas : Results, survival rates, and complications
Arvind Neelakantan, B Sridhar Rao, L Vijaya, N Krishnan, V Sita Priya
Smt. Jadhavbai Nathmal Singhvee Glaucoma Service, Medical Research Foundation, Madras 600 006, India
B Sridhar Rao
Vision Research Foundation, 18 College Road, Madras 600 006
Sixty-two single-plate single-stage Molteno implantations for complicated glaucomas were performed between March 1991 and November 1992. The charts of all these patients were reviewed to determine the intraocular pressure (IOP) control success rate (< 21 mm Hg with or without medications), visual success rate (retention or improvement of visual acuity from preoperative level) and the rate of complications encountered. A Kaplan-Meier life-table (survival) analysis was also performed. IOP control was obtained in 74.2% of cases. Mean postoperative IOP was 16.97 +/- 8.07 mm Hg (Mean +/- SD). Visual success was obtained in 51.6% of the eyes. Eyes with aphakia/pseudophakic glaucomas showed the best response with 80% of them achieving IOP control and 60% achieving visual success. The survival plot for IOP control revealed 75.81% and 74.19% success rates at 48 and 72 weeks, respectively. Complications encountered were either due to the early postoperative hypotony or were tube-related. These results were gratifying considering the severity of the glaucoma in these cases and they reaffirm the usefulness of the Molteno implant in the management of difficult glaucomas.
|How to cite this article:|
Neelakantan A, Rao B S, Vijaya L, Krishnan N, Priya V S. Single-plate Molteno implants in complicated glaucomas : Results, survival rates, and complications.Indian J Ophthalmol 1994;42:193-197
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Neelakantan A, Rao B S, Vijaya L, Krishnan N, Priya V S. Single-plate Molteno implants in complicated glaucomas : Results, survival rates, and complications. Indian J Ophthalmol [serial online] 1994 [cited 2020 Jun 3 ];42:193-197
Available from: http://www.ijo.in/text.asp?1994/42/4/193/25565
Implantation of setons has become a popular alternative to standard filtration procedures for the control of intraocular pressure (IOP), in glaucomatous eyes refractory to conventional techniques. Various types of foreign materials and devices have been implanted to facilitate the drainage of aqueous humour at the time of filtration surgery.  Molteno  has been responsible for the groundwork that has led to the development of the current generation of long-tube drainage devices. The single-plate Molteno implant consists of a polymethylmethacrylate (PMMA) episcleral plate 13 mm in diameter connected to the anterior chamber via a silicone rubber tube, and embodies the principles of an adequate drainage field, a permeable bleb over the field and a patent limbal fistula. A single plate or double plate may be used and the implantation may be a single-stage or a double-stage procedure.
We retrospectively analyzed the results of 62 single-plate Molteno implantations in 60 eyes for refractory glaucomas done at our centre from March 1991 to November 1992.
MATERIALS AND METHODS
Sixty-two eyes of 60 patients underwent a singlestage single-plate Molteno implantation at the Medical Research Foundation, Madras, from March 1991 to November 1992. All patients underwent a similar surgical procedure. A fornix-based conjunctival flap was raised in the superotemporal quadrant. A 3-0 prolene was used as a temporary stent to occlude the lumen of the Molteno tube in all eyes. The implant was sutured to the episcleral tissue 8 to 10 mm from the limbus by means of two 8-0 nylon sutures passing through the anterior holes in the plate. The tube was trimmed with the bevel facing forwards such that 1 to 2 mm of the tube entered the anterior chamber. A paracentesis was then performed with a 22-gauge needle and the Molteno tube was fed into the needle tract. A donor scleral patch graft (alcohol preserved) was used in all eyes to cover the exposed portion of the tube. The conjunctiva was then meticulously pulled over the implant and sutured back. The 3-0 prolene stent was tacked down to the inferior fornicial conjunctiva using a single 8-0 nylon suture. All patients had topical steroids and atropine postoperatively. No pharmacologic modulation of the bleb was used. The 3-0 prolene stent was removed 7 to 10 days postoperatively.
The charts of all the 60 patients were reviewed retrospectively. The results of the surgery were judged based on the last available information regarding their IOP levels and best-corrected visual acuity. Visual acuity success was defined as retention or improvement of vision from the preoperative level, whereas failure was a decrease of at least one line of visual acuity in the Snellen's chart, or a decrease in the visual level (counting fingers to hand motion). The IOP control was determined a success if the postoperative IOP was less than or equal to 21 mm Hg (with or without medications), irrespective of the preoperative IOP level. Kaplan-Meier life-table (survival) analysis for IOP success was performed due to the unequal lengths and frequencies of follow-up.
Of the 60 patients, 42 (70%) were males and 18 (30%) were females. The age of the patients ranged from 2 to 78 years (41.18 ± 21.64). The follow-up period varied from 5 to 75 weeks (21.76 ± 17.65) with 35.5% of patients having completed at least a six-month follow-up. Furthermore, 53.2% of the patients had undergone at least 2 or more previous surgical procedures [Table 1]. The various diagnostic categories included in this study are shown in [Table 2]. The preoperative IOPs ranged from 12 to 64 mm Hg (34.6 ± 10.3 mm Hg), with or without antiglaucoma medications.
The IOP was controlled in 74.2% of cases [Figure 1][Figure 2]. The mean postoperative IOP was 16.97 ± 8.01 mm Hg (Range, 2 to 39 mm Hg). The number of postoperative antiglaucoma medications ranged from 0 to 2 (0.48 ± 0.59 medications) with 36.5% of the patients requiring no medications postoperatively. Life-table (survival) analysis revealed a 75.81% and 74.19% IOP control success rate at 48 and 72 weeks, respectively [Figure 3].
A visual improvement was obtained in 32 of the 62 (51.61%) eyes [Figure 1]. In 2 patients, information on the visual acuity could not be obtained due to the young age of the patients.
[Table 3] analyses the surgical results in the different varieties of refractory glaucomas. The best results were obtained in the aphakic and pseudophakic glaucoma groups, both in terms of IOP control (80%) and vision (60%).
A wide range of postoperative complications were noted [Table 4]. Hypotony in the early postoperative period caused serous choroidal detachments in 14 (22.6%) patients and secondary retinal detachment in 4 (6.4%). Most of these resolved with a short course of systemic steroids. Surgical intervention was required in 2 patients due to their persistence. A choroidal tap with an anterior chamber reformation was done in these cases. One case of secondary retinal detachment progressed to no light perception and phthisis bulbi, despite all treatment measures.
Tube-related complications such as cornea-tube touch, tube occlusion, etc., were noted later in the postoperative period. Of the 5 patients with a corneatube touch, only one patient required a penetrating keratoplasty. The tube was occluded in 3 patients; due to vitreous in one, and iris in the other two. Nd:YAG laser vitreolysis was successful in reopening of the tube lumen in the first case and in another patient the iris was retracted with a combination of Nd:YAG and argon blue-green laser. Erosion of the tube through the scleral graft was seen to occur in one case and it was treated with an emergency scleral patch graft. Tube sliding was seen to occur in only a single case. Interestingly, in this patient, the equatorial bleb eventually ruptured and Molteno plate was exposed. An emergency removal of the implant was performed. Despite a good postoperative IOP control, four patients progressed to no light perception due to the progressive nature of the retinal disease. Most of the complications encountered were managed successfully with the instituted therapy.
When evaluating newer surgical techniques for refractory glaucomas, one must take into consideration the potential for higher incidence of complications and unusual postoperative responses in these eyes than in eyes with less advanced disease. Previously reported surgical success rates with the Molteno implant in complicated glaucomas have varied from 34% to 95%, although comparison amongst them is difficult because of the different types of patients, the lack of uniform success criteria, variable use of postoperative systemic antifibrosis therapy and variable followup periods. 
Molteno  reported a series of 110 patients and showed a success rate of 93% (IOP  Brown and Cairns sub in two studies, one evaluating neovascular glaucomas and the other an assortment, showed a 75% and 50% success rate, respectively (IOP  have reported an 84% success rate (TOP  have reported the results of a 5-year study of single-plate Molteno implants in complicated glaucomas. They report that IOP was controlled in 46% of aphakic and pseudophakic eyes, 25% of eyes with failed filters, 25% in eyes with neovascular glaucoma and a 26% success rate in patients younger than 13 years (6 mm Hg  Heuer et a1  presenting the results of a randomized clinical trial of single-versus double-plate Molteno implants reported a 1-and 2-year survival rate of 55% and 46%, respectively, for the single-plate implant.
Most of the complications reported in our study have been reported earlier. Lloyd et a1  reported the following complications: corneal oedema (19%), graft decompensation (13%), cornea-tube touch (8%), retinal detachment (8%), and cataract (8%). Lotufo  reported a series of 16 cases where early and late postoperative complications were reported in 75% and 50% of cases, respectively. The early onset complications were transient and associated with hypotony. The late onset ones had a poorer visual prognosis and included implant extrusions, vitreous haemorrhage, cystoid macular oedema, and tractional retinal detachment.  Melamed et al  have also reported similar complications. Munoz and Parrish  have reported a case of restrictive hypertropia following a superotemporal single-plate Molteno implantation.  Late infectious endophthalmitis from exposed glaucoma setons has also been reported.  Mermoud et a1  have analyzed the long-term results in neovascular glaucoma, which was found to be poor mainly due to the underlying retinal disease.
In our series most of the postoperative complications could be attributed either to the early postoperative hypotony or were tube-related. We used a 3-0 prolene stent to occlude the tube in the early postoperative period as practised by Egbert and Lieberman  as well as by Hoare Nairne et a1 . A variety of other methods to prevent this early postoperative hypotony seen commonly with this class of implants have been described, which includes a dual chambered Molteno implant. 
A transient ocular hypertension, 4 to 12 weeks following surgery has been reported as a predictable and reversible event in the course of most glaucoma implant surgeries. Most investigators are of the opinion that although, the preoperative glaucoma medications are often resumed during this transient phase, with time the need for these subside and the long-awaited surgical control manifests.  Molteno has also reported a steroid response that can occur after more than 6 weeks of application of steroids following surgery.  In this study, 12 eyes reported as failures with respect to pressure control, are thought to be in this hypertensive phase. Hence, a longer follow-up may possibly help in enhancing the success rate.
Current evidence indicates that two Molteno plates achieve a better IOP control than a single plate, , but the incidence of complications related to hypotony appear to be higher. In single-plate Molteno surgery IOP control has been seen to decline postoperatively over several years and the surgical success rates have been noted to improve somewhat with additional plates, but whether two single plates are as effective as a double-plate implant remains to be seen. 
The future lies in developing shunts that incorporate reliable structure resistance or valves, incorporating bleb modifying pharmacological agents in the polymer matrix of the implants and the concurrent use of antimetabolites along with the implants. 
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