|Year : 2015 | Volume
| Issue : 1 | Page : 22-26
Decapsulation versus valve reimplantation in cases with an encysted Ahmed valve in refractory glaucoma
Salah M Al-Mosallamy
Department of Ophthalmology, Zagazig University, Zagazig, Egypt
|Date of Submission||02-Jul-2014|
|Date of Acceptance||15-Oct-2014|
|Date of Web Publication||29-May-2015|
MD Salah M Al-Mosallamy
Ophthalmology Department, Zagazig University, Zagazig 44519
Source of Support: None, Conflict of Interest: None
The aim of the study was to evaluate the efficacy and safety of decapsulation of the fibrous capsule around the valve body versus valve reimplantation in another site in refractory glaucoma cases.
Patients and methods
We studied 25 cases with refractory glaucoma that had been implanted with an Ahmed glaucoma valve; their intraocular pressure (IOP) was greater than 21 mmHg and had undergone additional maximum topical antiglaucoma therapy. Patients were divided into two groups according to the surgical treatment that had been performed: group I included 12 eyes that had been treated by surgical decapsulation of the cyst around the valve body without removal of the valve and group II included 13 eyes treated by removal of the valve and reimplantation in another quadrant of the eye.
Of the 25 patients included in the study, 15 were male and 10 were female, with a mean age of 19.2 ± 9.2 years in group I and 22.1 ± 10.3 years in group II. Recurrent congenital glaucoma was the most common preoperative diagnosis in both groups (50 and 53.8% in groups I and II, respectively). There was no statistically significant difference between the two groups regarding preoperative patient demographic characteristics (P < 0.05). The surgical results revealed that the mean operation time was significantly lower in group I than in group II (30 ± 12 and 45 ± 13.5 min, respectively; P = 0.023). However, there were no statistically significant differences in the success (complete and partial) and failure rates between the two groups (P < 0.05). There was marked reduction in IOP from preoperative values in both groups but there were no significant differences in IOP levels between the two groups over the follow-up visits. Tube-related complications occurred in group II only and included corneal tube touch in one (7.7%) case and erosion of the tube covering in two (15.4%) cases. One of them developed endophthalmitis and then lost the perception of light (PL) and ended in phthisis bulbi. Recurrence of encapsulation occurred more in group I (three cases, 25%) than in group II (two cases, 15.4%), after a mean postoperative time of 23 ± 2 weeks. The incidence of valve re-encapsulation was statistically insignificant between the two groups (P = 0.09).
Both surgical techniques were effective in controlling IOP in cases with encapsulated Ahmed valve; however, the decapsulation technique was simpler with shorter operation time and no probability for tube-related complications. Although the other technique of valve reimplantation had a longer operation time and more tube-related complications, it was associated with less incidence of re-encapsulation. However, larger multicenter studies with longer follow-up are needed for validation of these treatment strategies.
Keywords: ahmed glaucoma valve, decapsulation, refractory glaucoma
|How to cite this article:|
Al-Mosallamy SM. Decapsulation versus valve reimplantation in cases with an encysted Ahmed valve in refractory glaucoma. Delta J Ophthalmol 2015;16:22-6
|How to cite this URL:|
Al-Mosallamy SM. Decapsulation versus valve reimplantation in cases with an encysted Ahmed valve in refractory glaucoma. Delta J Ophthalmol [serial online] 2015 [cited 2018 Dec 9];16:22-6. Available from: http://www.djo.eg.net/text.asp?2015/16/1/22/157784
| Introduction|| |
Surgical treatment of glaucoma - namely, filtering surgery such as trabeculectomy - is performed as a standard procedure. However, in cases of refractory glaucoma, including neovascular glaucoma, uveitic glaucoma, aphakic or pseudophakic glaucoma, and glaucoma after penetrating keratoplasty, the success rate of trabeculectomy is reported to be low , . Glaucoma drainage devices provide an alternative mode of treatment in complicated and refractory glaucoma cases , . This surgical option is being used with increasing frequency, especially valved devices such as the Ahmed glaucoma valve (AGV). The clinical success of such devices is often limited by excessive wound healing and scar formation around the base plate of the implant. In severe cases, which seem to occur most frequently in pediatric patients, the rapid formation of a thick, water-impervious fibrotic capsule within months after initial implantation leads to diminished aqueous resorption and an increase in intraocular pressure (IOP) to presurgical values. Often, additional surgical interventions become necessary  .
The cystic wall of these encapsulated blebs (EBs) had an overall thickness of 1.5-2 mm. Histopathologically, the smooth inner surface (facing the base plate of the AGV) consisted of tightly packed collagen fibers with signs of elastoid degeneration, and formation of a pseudoendothelium toward the base plate. There was pronounced transformation of fibroblasts into myofibroblasts in this inner layer. The outer area was highly vascularized. In these vessels electron microscopy revealed thrombosis  . The incidence of bleb encapsulation has ranged from 2.5 to 29% in various surgical techniques performed in different types of glaucoma, being higher in drainage devices and much lower in trabeculectomy, with no histopathological difference between them ,, . The treatment options in these cases include needling and mitomycin C usage but with limited success  , surgical excision of the cystic wall with application of mitomycin C, or valve removal and reimplantation in another site  . This study was designed to evaluate the results of decapsulation versus reimplantation of AGV in refractory glaucoma.
| Patients and methods|| |
A retrospective study that included a total of 25 eyes of 25 patients were reviewed from those operated upon in the Ophthalmology Department of Zagazig University Hospital during the period October 2012 to April 2013. Fifteen patients were male and 10 were female, aged between 2 and 65 years with a mean ± SD age of 47.6 ± 3.1 years.
All patients diagnosed with refractory glaucoma who had implanted AGV and IOP greater than 21 mmHg and had undergone additional maximum topical antiglaucoma therapy were included in the study. Before enrollment, patients (or their parents in cases of children) were informed of the procedures and the aim of the study and they signed informed consent forms to participate in the study according to the Declaration of Helsinki (1983).
Patients with no PL or who had undergone previous cyclodestructive procedures or recurrent cystic AGV were excluded.
Patients were divided into two groups according to the surgical treatment that had been performed: group I included 12 eyes that had been treated by surgical decapsulation of the cyst around the valve body without removal of the valve; group II included 13 eyes that had been treated by removal of the valve and reimplantation in another quadrant of the eye.
Preoperative evaluation of the patients included demographic data that included age, sex, surgical histories including preoperative diagnosis, details of the surgical technique, especially the type and size of AGV used, follow-up duration, and operative and postoperative complications of the previous surgeries. Thorough ophthalmic examinations were performed. IOP was measured using Goldman applanation tonometry; anterior and posterior segments were evaluated with special attention to the cystic valve plate, and the anterior chamber (AC) AGV tube was noted. Children were examined under general anesthesia before surgery. These included measurement of IOP using a Perkins tonometer and corneal diameter using a caliper. The AC depth and corneal clarity were also recorded. Fundus examination by direct and indirect ophthalmoscopy was performed depending on clarity of the media. Patients were divided into two groups: group I included the patients treated by decapsulation of AGV with mitomycin C and group II included patients treated with valve removal and reimplantation at another site using mitomycin C.
All patients were operated upon under general anesthesia. An EB was noted as an elevated, smooth-surfaced, tense, thickened, dome-shaped fibrotic membrane over the valve plate. EB removal was carried out as follows: after traction sutures using 8/0 silk sutures, the eye was rolled downward exposing the cyst. The conjunctiva and Tenon were then dissected and the EB was directly opened. A gush of aqueous humor was noted on opening the cyst and the IOP became soft. The fibrotic capsule was carefully removed from all around the valve plate, along with as much tissue as possible. A sponge soaked with mitomycin C (0.4 mg/ml) was then applied on the exposed surface of the valve plate and covered with conjunctiva and kept in place for 3 min. The sponge was then removed and the area was irrigated with 50 ml of balanced saline solution. The wound was then closed using 8/0 silk sutures. Subconjunctival administration of dexamethasone and gentamicin, together with topical steroid antibiotic, was performed postoperatively [Figure 1].
The technique of reimplantation of Ahmed glaucoma valve
After opening the cyst as described earlier, the valve was removed and the conjunctiva was closed using 8/0 silk sutures. The valve was reimplanted in another eye quadrant using a standard technique. The superotemporal or superonasal quadrant was used for implant fixation in all eyes. A fornix-based conjunctival flap and Tenon's capsule were dissected to allow insertion of the plate of the implant into the sub-Tenon space 8 mm behind the corneal limbus. Before insertion of the plate, a sponge soaked with mitomycin C (0.4 mg/ml) was applied to the exposed surface of the sclera and covered with conjunctiva and kept in place for 3 min. Thereafter, the sponge was removed and the area was irrigated with 50 ml of balanced salt solution. The valve was primed by irrigating the lumen of the tube with balanced salt solution. The plate was fixed to the sclera with two 8/0 virgin silk sutures (Ethilon; Ethicon US, LLC). The tube was shortened to the desired length (allowing 1-2 mm in the AC) with its sharp bevel facing anteriorly. An AC paracentesis wound was created at the peripheral cornea using a keratome (no. 15) to allow AC reformation if needed. A long scleral flap was then fashioned to cover as much as possible of the valve tube. The tube of the implant entered the AC parallel to the iris plane and under the scleral flap through the sclerostomy created with a 23-G syringe needle. The flap was fixed to the sclera using two 8/0 virgin silk sutures. The patients received postoperative treatment similar to group I patients [Figure 2].
The patients were followed up at 1 day, 1 week, and 1 month and every 2 months for 12 months postoperatively; at each visit a thorough ophthalmic examination was conducted. Children were examined under general anesthesia.
Absolute success was defined as IOP equal to or less than 21 mmHg and equal to or greater than 5 mmHg without antiglaucoma medications or additional glaucoma surgery and without visually devastating complications such as endophthalmitis or phthisis bulbi and no loss of light perception. Partial success was considered when the above criteria were fulfilled but with the administration of antiglaucoma topical treatment.
Data were collected, tabulated, and statistically analyzed for the detection of significant values. This was done using Microsoft Excel 2007 (USA) to calculate the mean ± SD. The Student t-test was used to compare means and the Kruskal-Wallis test was used to compare the percentage values. P values greater than 0.05 were considered nonsignificant, values less than 0.05 were considered significant, and values less than 0.01 were considered highly significant.
| Results|| |
Of the 25 cases included in the study, 15 were male and 10 were female, with a mean age of 19.2 ± 9.2 years in group I and 22.1 ± 10.3 years in group II. Congenital glaucoma was the most common preoperative diagnosis in both groups: 50 and 53.8% in groups I and II, respectively. There were no statistically significant differences between the two groups with respect to preoperative demographic characteristics of patients (P < 0.05).
The surgical results revealed that the mean operation time was significantly lower in group I than in group II (30 ± 12 and 45 ± 13.5 min, respectively; P = 0.023). In addition, there were no statistically significant differences in the success - whether complete or partial - and failure rates between the two groups (P < 0.05) [Table 1].
[Table 2] shows marked reduction in IOP from preoperative values in both groups, but there was no significant difference in IOP levels between the two groups over the follow-up visits.
|Table 2: Mean intraocular pressure of the two studied groups over follow-up visits|
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Tube-related complications occurred in group II only, which were corneal tube touch in one (7.7%) case and erosion of the tube covering in two (15.4%) cases [Table 2]. In case of corneal tube touch, a small localized corneal opacity overlying the tube occurred; this did not progress to corneal decompensation. Tube erosion required reoperation, in which a donor scleral graft was used with Tenon and conjunctival advancement to cover the graft over the tube. Erosion did not recur, but one case developed endophthalmitis 3 days after the reoperation of tube coverage, which was managed by systemic and topical fortified antibiotic eye drops according to culture and sensitivity tests of the aqueous and vitreous samples. Intravitreal and subconjunctival injections were also given. The inflammation of the eye subsided but unfortunately it lost the PL and ended in phthisis bulbi and was considered a failure. Recurrence of encapsulation occurred more in group I (three cases, 25%) than in group II (two cases, 15.4%) after a mean time of 23 ± 2 weeks postoperatively. It manifested as large dome-shaped elevation of the conjunctiva and Tenon's capsule over the valve body, together with high IOP, and was managed with eye drops. Two cases in group I and one case in group II maintained adequate IOP until the end of follow-up and were considered as partial success. One case in each group required reoperation to control IOP in which decapsulation with mitomycin C was used. IOP was controlled in each but they were considered as failure because they required additional surgery to control the IOP. The incidence of valve re-encapsulation was statistically insignificant between the two groups (P = 0.09) [Figure 3] and [Table 3] and [Table 4].
| Discussion|| |
Success after AGV implant insertion can be measured by lowering the IOP and reducing the number of antiglaucoma medications needed. An encapsulated cyst (also called Tenon's cyst) develops when Tenon's capsule adheres to the episclera, forming a high, domed, smooth, two-layered bleb. The encapsulated cyst is impermeable to aqueous humor, which results in IOP elevation. With excessive fibrosis and persistent IOP elevation, further intervention may be necessary , . Excision of the fibrotic tissue around the implant may help salvage function and might be an alternative to the more commonly practiced reimplantation of another valve  .
In this study 15 patients were male and 10 were female, with a mean age of 19.2 ± 9.2 years in group I and 22.1 ± 10.3 years in group II. Congenital glaucoma was the most common preoperative diagnosis in both groups: 50 and 53.8% in groups I and II, respectively. There were no statistically significant differences between the two groups regarding preoperative patient demographic characteristics. The surgical results showed that the mean operation time was significantly lower in group I than in group II (30 ± 12 and 45 ± 13.5 min, respectively). This was attributed to the fact that in the decapsulation operation there is no cautarization, fashioning, and resuturing of the scleral flap, nor valve priming and tube introduction into the AC. There was also no statistically significant difference in the success (complete and partial) and failure rates between the two groups. There was marked reduction in IOP from preoperative values in both groups but there were no significant differences in IOP levels between the two groups over the follow-up period. This reflects that both techniques can be used in the management of valve encapsulation.
Tube-related complications occurred in group II only, which included corneal tube touch in one (7.7%) case and erosion of the tube covering in two (15.4%) cases. One of them developed endophthalmitis; this case lost the PL and ended in phthisis bulbi. This tube-related complication did not occur in group I because the tube and valve were kept in place in decapsulation. Moreover, removal of the valve and its reimplantation (in group II) carry the risk of implantation in an area of thin sclera, which predisposes to tube erosion, because most of the cases in the study were operated upon many times. Although the recurrence of encapsulation occurred more in group I (three cases, 25%) than in group II (two cases, 15.4%), the difference was statistically insignificant. All of these cases occurred after a mean time of 23 ± 2 weeks postoperatively and were manifested by a large dome-shaped elevation of the conjunctiva and Tenon's capsule over the valve body, together with high IOP. The higher incidence of re-encapsulation in group I can be explained by the fact that cutting and excision of the capsule and Tenon around the valve may induce low-grade inflammation with fibrovascular in-growth postoperatively, resulting in more fibrous tissue capsule formation; fortunately, mitomycin C application decreased this incidence.
Lai et al.  found that decapsulation succeeded in controlling the IOP in all cases in which it was performed; however, the number of such cases was only six. In a larger study performed by Eibschitz-Tsimhoni et al.  a 73% (8/11 cases) success in decapsulation was reported, and IOP was normalized and maintained for 330 ± 120 days during follow-up, which demonstrated the beneficial effect of surgical cyst excision on lowering IOP when medical therapy or needling are insufficient. To our knowledge, there are no previous studies that have compared the results of surgical decapsulation of encapsulated Ahmed valve against valve reimplantation.
| Conclusion|| |
Both surgical techniques were effective in controlling IOP in cases with an encapsulated Ahmed valve. However, the decapsulation technique was simpler with shorter operation time and no possibility for tube-related complications. Although other techniques of valve reimplantation had longer operation time and more tube-related complications, it is associated with less incidence of re-encapsulation. However, larger multicenter studies with longer follow-up are needed before establishment of these treatment strategies.
| Acknowledgements|| |
Conflicts of interest
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4]