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ORIGINAL ARTICLE
Year : 2015  |  Volume : 22  |  Issue : 1  |  Page : 64-68  

Outcomes of Ahmed valve implant following a failed initial trabeculotomy and trabeculectomy in refractory primary congenital glaucoma


1 VST Glaucoma Centre, Kallam Anji Reddy Campus, Hyderabad, Andhra Pradesh; Department of Glaucoma, Dr. TV Patel Eye Institute, Salatwada, Vadodara, Gujarat, India
2 VST Glaucoma Centre, Kallam Anji Reddy Campus, Hyderabad, Andhra Pradesh, India

Date of Web Publication1-Jan-2015

Correspondence Address:
Paaraj Dave
Dr. TV Patel Eye Institute, Vinoba Bhave Road, Salatwada, Vadodara 390 001, Gujarat
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0974-9233.148351

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   Abstract 

Purpose: The aim was to report the outcome of Ahmed glaucoma valve (AGV) (New World Medical, Inc., Rancho Cucamonga, CA, USA) implantation as a surgical intervention following an initial failed combined trabeculotomy + trabeculectomy (trab + trab) in refractory primary congenital glaucoma (RPCG).
Materials and Methods: Retrospective chart review of 11 eyes of 8 patients who underwent implantation of AGV (model FP8) for RPCG between 2009 and 2011. Prior trab + trab had failed in all the eyes. Success was defined as an intraocular pressure (IOP) >5 and ≤ 18 mmHg during examination under anesthesia with or without medications and without serious complications or additional glaucoma surgery.
Results: The mean age at AGV implantation was 15.4 ± 4.9 months. The mean preoperative IOP was 28 ± 5.7 mmHg which reduced to 13.6 ± 3.4 mmHg postoperatively at the last follow-up (P < 0.0001). The number of topical antiglaucoma medications reduced from a mean of 2.6 ± 0.5 to 1.6 ± 0.9 postoperatively (P = 0.009). The definition of qualified success was met in 10 (90%) eyes. One eye developed a shallow anterior chamber with choroidal detachment at 1-week, which resolved spontaneously with medications. None of the eyes developed a hypertensive phase. One eye had a long tube resulting in tube corneal touch that required trimming of the tube. One eye developed tube retraction, which was treated with a tube extender. The mean follow-up was 17.9 ± 9.3 (6.2-35.4) months.
Conclusion: Managing RPCG remains a challenge. AGV implant was successful in a significant proportion of cases.

Keywords: Ahmed Valve Implant, Failed Trabeculotomy and Trabeculectomy, Refractory Congenital Glaucoma


How to cite this article:
Dave P, Senthil S, Choudhari N, Sekhar GC. Outcomes of Ahmed valve implant following a failed initial trabeculotomy and trabeculectomy in refractory primary congenital glaucoma. Middle East Afr J Ophthalmol 2015;22:64-8

How to cite this URL:
Dave P, Senthil S, Choudhari N, Sekhar GC. Outcomes of Ahmed valve implant following a failed initial trabeculotomy and trabeculectomy in refractory primary congenital glaucoma. Middle East Afr J Ophthalmol [serial online] 2015 [cited 2019 Nov 22];22:64-8. Available from: http://www.meajo.org/text.asp?2015/22/1/64/148351


   Introduction Top


The treatment of pediatric glaucoma is quite taxing due to the poor response to medical therapy and the inability of the child to cooperate fully for a comprehensive examination. Surgery is the mainstay of treatment whereas medical therapy is primarily utilized as an adjunct to lower the intraocular pressure (IOP) temporarily. [1],[2]

Combined trabeculotomy + trabeculectomy (trab + trab) has been shown to have good results and has become the procedure of choice especially in India where severe corneal clouding at birth in patients of primary congenital glaucoma precludes a goniotomy. [3],[4],[5] Even in the best of hands, trab + trab for primary congenital glaucoma has a failure rate of up to 20% at 1-year and additional surgery is often required to control the IOP in the long-term. [6] The management options after a failed trab + trab are trabeculectomy augmented with antimetabolite, aqueous drainage implant and trans-scleral cyclophotocoagulation (TSCPC). [6]-[8]

Trabeculectomy with mitomycin-C in refractory pediatric glaucoma has shown promise, with studies reporting 52-95% success rates. [9],[10],[11] However, the increased success with the addition of antimetabolites has also resulted in well recognized long-term complications such as bleb failure, bleb leak, and bleb related endophthalmitis. [11],[12],[13]

Cycloablative therapy can be considered for refractory cases, but success rates are limited with difficult titration, re-treatments and serious complications like retinal detachment and phthisis bulbi. [14],[15],[16] Hence, it is reserved for eyes with low or nil visual potential or for those eyes where implant surgery is not possible. Glaucoma drainage devices (GDD) offer the potential advantage over trabeculectomy by being technically feasible in the presence of conjunctival scarring or in buphthalmic eyes with very thin sclera. Because the "bleb" of the GDD is formed far posterior to the limbus, the long-term risk of devastating bleb or intra-ocular infection is theoretically lower than with trabeculectomy. Ahmed glaucoma valve (AGV) implant (New World Medical, Inc., Rancho Cucamonga, CA, USA) has a unidirectional protective valve that is designed to open at a pressure of 8 mmHg, potentially decreasing the risk of postoperative hypotony. Ahmed valve implantation in childhood glaucomahas probabilities of success ranging from 70% to 93% at 12 months and 58 to 86% at 24 months. [17],[18],[19],[20] These reports include children with congenital glaucoma as well as children with secondary diagnoses including aphakia or pseudophakia, Sturge-Weber syndrome, uveitic glaucoma, aniridia and anterior segment dysgenesis. Earlier, only Ou et al. [21] has reported on the outcome of Ahmed valve implantation in children with primary congenital glaucoma who underwent prior glaucoma surgery. Chen et al. [22] evaluated the outcome of AGV in refractory pediatric glaucoma. They reported a higher incidence of failure in children with primary congenital glaucoma (55%). However, there is no study reporting the outcome of Ahmed valve implantation in children with primary congenital glaucoma following an initial combined trab + trab procedure.


   Materials and Methods Top


This is a retrospective noncomparative case series of eyes with a diagnosis of primary congenital glaucoma that underwent implantation of AGV (model FP8) following a failed primary trab + trab from 2009 to 2011 at a tertiary care ophthalmic center. An institutional review board approval was obtained.

The records of 53 patients with an initial diagnosis of congenital glaucoma that underwent primary trab + trab were reviewed. Repeat procedures were required in 15 eyes. Four eyes had secondary glaucoma's and were excluded. AGV implant without additional procedures was done in 8 eyes. Two eyes underwent TSCPC prior to the AGV implant. One eye had an AGV implant after a repeat trabeculectomy. Hence, 11 eyes of 8 patients were included in the final analysis.

The preoperative clinical data included the patient's age at surgery, gender, diagnosis, history of prior ocular surgeries and details of antiglaucoma medication. All patients had an examination under anesthesia (EUA) prior to the surgery. The details noted included findings on slit lamp examination, corneal diameter, retinoscopy, IOP measurement and direct and indirect ophthalmoscopy. All patients with a hazy view of the fundus had a B-scan done. IOP was measured as soon as possible under Sevoflurane anesthesia with a Perkins tonometer wherever possible or a tonopen in cases with scarred cornea. All surgeries were done by a single experienced glaucoma surgeon (SIR) under general anesthesia. Postoperatively, the patient was seen on day 1 in the OPD. EUA was done at 1 st week, 1-month, and 2-3 monthly thereafter. Follow-up examination included portable slit lamp examination for corneal clarity, retinoscopy, measurement of corneal diameter and IOP, disc and retinal evaluation, implant tube position, scleral patch coverage and bleb appearance. Visual acuity (Teller acuity charts) was assessed wherever possible. Postoperative regimen included topical steroids, antibiotics and cycloplegic eye drops. Topical steroids were gradually tapered over a period of 6 weeks. Topical glaucoma medications were added on the discretion of the treating surgeon.

Surgical technique

Surgical site was exposed with a corneal traction suture using 8-0 polyglactin sutures (Vicryl; Ethicon, Inc., Somerville, New Jersey, USA). A limbal-based conjunctival flap was created in the supero-temporal or supero-nasal quadrant and conjunctival pocket was dissected between the superior and lateral rectus muscles. Sclera was exposed using blunt dissection. The implant was gently primed using balanced salt solution. The implant plate was secured to the underlying sclera between the rectii muscles using two 10-0 polypropylene sutures (Prolene; Ethicon, Inc., Somerville, New Jersey, USA) making sure the anterior edge of the implant is 8-10 mm posterior to the surgical limbus. A 23-gauge needle was used to enter the anterior chamber 2 mm behind the surgical limbus parallel to the iris. The tube was trimmed bevel up leaving adequate length of the tube so that 2-2.5 mm tube would be in the anterior chamber after insertion. The tube was inserted with a special forceps into the AC and secured to the sclera using a 10-0 nylon suture (Ethilon; Ethicon, Inc., Somerville, New Jersey, USA). A donor scleral flap was used to cover the tube and secured to the sclera either with10-0 nylon sutures or using fibrin glue in eyes with thin sclera. Conjunctiva was re-apposed using 8-0 polyglactin sutures (Vicryl; Ethicon, Inc., Somerville, New Jersey, USA). The eye was patched and shielded after instillation of betadine 2.5% eye drops.

The primary outcome measure was IOP at 1-year. Complete success was defined as an IOP > 5 and ≤ 18 mmHg during EUA without any glaucoma medications. Qualified success was defined as an IOP > 5 and ≤ 18 mmHg during EUA with medications (a maximum of 3 topical antiglaucoma medications). Serious complications (suprachoroidal hemorrhage, retinal detachment or endophthalmitis) or additional glaucoma surgery was considered as failure. Hypertensive phase was defined as an IOP >21 mmHg at anytime with/without medications during first 3 postoperative months after ruling out other causes like tube obstruction.

Statistical analysis

Descriptive and inferential statistics were performed using STATA version 11 for Windows (StataCorp LP, Texas, USA). Paired t-test was used to compare the IOP and the number of glaucoma medications before and after the intervention.


   Results Top


Eleven eyes of eight patients were included in the study. Patient demographics are summarized in [Table 1]. The mean age at surgery was 15.4 ± 4.9 months. There were 4 male and 4 female patients. The mean preoperative IOP was 28 ± 5.7 mmHg, which reduced to 13.6 ± 3.4 mmHg postoperatively at the last follow-up (P < 0.0001). The IOP at 1-week, 1-month, 3 months, 6 months and 1-year was 9.7 ± 1.5, 13.2 ± 3.7, 11.7 ± 2.5, 13 ± 2.5 and 12.6 ± 2.8 mmHg, respectively. This along with the number of patients at each time point is shown in the box plot [Figure 1]. The number of topical antiglaucoma medications reduced from 2.6 ± 0.5 to 1.6 ± 0.9 postoperatively at the last follow-up (P = 0.009). Complete success was achieved in only 3 out of the 11 eyes. Ten out of the 11 eyes achieved qualified surgical success as defined at 1-year. Some eyes had additional glaucoma procedures done after the primary combined trab + trab prior to the AGV implantation. Two eyes had a trans-scleral cyclophotocoagulation done. One eye had a repeat trabeculectomy done after which the AGV was implanted.
Figure 1: Box plot showing the intraocular pressure change at various follow-ups from the preoperative value

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Table 1: Demographics

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One eye had developed choroidal detachment at 1-week postoperative visit which resolved after a week with conservative treatment. None of the eyes developed hypertensive phase. One eye had a long tube resulting in tube corneal touch. In the follow-up period we noticed corneal haze and edema corresponding to the portion of the tube end. Though there was tube malposition, eye rubbing by the child may have been an additional factor resulting in tube corneal touch. Trimming of the tube was done 11 months after implantation of AGV. One eye developed tube retraction after 8 months of AGV implantation which was treated by a tube extender. No sight threatening complications were noted. The mean follow-up was 17.9 ± 9.3 (6.2-35.4) months. The patient data is summarized in [Table 2].
Table 2: Patient summary data


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   Discussion Top


Primary congenital glaucoma is distinct from other secondary pediatric glaucomas. It is primarily managed surgically, medications are not effective and 20% of the primary surgeries fail at the end of 1-year. The choice of second procedure in these eyes is debatable and range from trabeculectomy with MMC, tube implants to TSCPC. When failure of the primary surgery is detected and treated promptly, majority of these eyes can be prevented from going blind. Owing to the rarity of the disease, there are no randomized control trials evaluating the efficacy of the various modalities of treatment for PCG. In PCG, it is a bigger challenge since there is evidence in literature reporting higher incidence of failure of AGV in PCG compared to other secondary glaucomas. [22] The advance nature and increased severity of the disease in patients undergoing AGV implantation could be responsible for the higher failure rate.

Chen et al. [22] evaluated the outcome of AGV in refractory pediatric glaucoma. They reported a higher incidence of failure in children with primary congenital glaucoma (55%) compared with glaucoma in aphakia, Sturge-Weber syndrome, aniridia, uveitis and those with persistent primary hyperplastic vitreous. Coleman et al. [17] also suggested a higher risk of failure in eyes with primary congenital glaucoma than in those with other diagnoses. Englert et al. [19] however, reported success in 13 out of the 14 eyes (92.9%) with refractory primary congenital glaucoma (RPCG) after AGV implantation. In our series, qualified success was achieved in ten out of 11 eyes (90%).

Djodeyre et al. [18] have reported that a diagnosis of congenital glaucoma, number of previous glaucoma procedures and the surgeon's experience were related to the survival of the Ahmed implant. In our series, all the surgeries were performed by a single experienced surgeon and none of the eyes had more than 2 antiglaucoma procedures done. Englert et al. [19] also reported that eyes, which had a previous cycloablation had a lower mean postoperative IOP. A prior TSCPC was done in 2 of our 11 patients. All these could be the reasons for a high qualified success rate, as defined, in our series. The success rates for congenital glaucoma tend to decrease with time. A study by Ou et al. [21] reported a cumulative success rate of 63% in their series at 1-year that reduced to 33% at 5 years. In a series of 32 patients of primary congenital glaucoma, O'Malley Schotthoefer et al. [23] reported a 1-year cumulative success rate of 92% which fell to 42% at 10 years. It would be interesting to note whether the same trend is followed in our series over a period of time. Postoperative hypotony with Ahmed valve in children is reported to be less common, 11-14%. [17],[19] In the larger series reported by Djodeyre et al. [18] the hypotony rate was 25%. In our study, one out of the eleven eyes developed this complication (9.1%).

The study by Chen et al. [22] reported a hypertensive phase in 13 out of the 52 eyes (25%). Due to the advanced nature of optic nerve damage in our series, ten out the eleven eyes were started on topical glaucoma medications from day 1 postoperatively. Early aqueous suppression has been shown to improve outcomes in terms of IOP reduction, success rate and hypertensive phase frequency. [24] This could be the reason why there were no eyes with a hypertensive phase in our series. Three out of the 11 eyes could be weaned off the glaucoma medications completely by the last follow-up.

Tube - related problem, especially tube corneal apposition, was the most common complication reported by Ou et al. [21] Four eyes (13%) in their series necessitated tube trimming. This complication was seen in 1 out the 11 eyes in our series (9.1%). It is postulated that vigorous eye rubbing can move the tube forward toward the cornea. Also, as the child's eye grows, the initially well-positioned tube may rotate more anteriorly over time. In our patient, eye rubbing could have been the cause for tube corneal touch.

Eye growth also results in tube retraction, which was seen in 1 eye (9.1%) in our series and was treated with a tube extender.

To the best of our knowledge, there are no studies reporting the outcome of AGV implantation after a primary combined trab + trab in primary congenital glaucoma. With primary trab + trab fast becoming the initial surgical procedure of choice, this scenario is likely to be faced by more and more surgeons in near future. Our study is limited by its retrospective design; small sample size and variable follow-up. With longer follow-ups, additional aqueous drainage device failures may occur in future. In addition, due to the inability to perform the visual acuity testing in all eyes, nothing can be commented on the visual outcome. The strength of the study lies in its uniform grouping of patients and the type of the GDD used.

Managing RPCG remains a difficult clinical problem. Medical treatment alone often fails. AGV implant is an effective alternative in these cases.

 
   References Top

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