|Year : 2013 | Volume
| Issue : 3 | Page : 188-193
Trabeculectomy assisted by collagen matrix implant (Ologen) in primary congenital glaucoma
Momen M Hamdi
Department of Ophthalmology, Ain Shams University, Cairo, Egypt
|Date of Submission||15-May-2013|
|Date of Acceptance||16-Jun-2013|
|Date of Web Publication||28-Feb-2014|
Momen M Hamdi
Ophthalmology Department, Ain Shams University, 11566 Cairo
Source of Support: None, Conflict of Interest: None
The primary objective of the study was to evaluate the efficacy and safety of collagen matrix (CM) Ologen in subscleral trabeculectomy (SST) for the treatment of primary congenital glaucoma (PCG).
Patients and methods
Three children with PCG were operated upon with SST assisted by Ologen. The CM was inserted over the scleral flap under the fornix-based conjunctival flap. Tight closure of the conjunctiva was performed. The first child was a 3-year-old boy with left PCG not operated upon, with intraocular pressure (IOP) of 45 mmHg. The second infant was 7 months old with left recurrent PCG after failed SST with antifibrotic agent mitomycin-C followed by needling performed twice; IOP was 30 mmHg under medications. The third child was a 7-year-old girl with right recurrent PCG after SST at the age of 25 days; IOP was 28 mmHg under medications.
Follow-up was planned under general anesthesia at 1 week, 1, 3, and 6 months. Parameters used were IOP measurement, corneal diameter, corneal clarity, cup-disc ratio, and state of the bleb. Photographs were taken at different visits to assess the shape, extent, and vascularity of the bleb.
The definition of success was as follows:
(1) Full success: IOP less than 15 mmHg without medications; clear cornea.
(2) Satisfactory success: IOP less than 21 mmHg without medications; clear cornea.
(3) Poor success: IOP less than 21 mmHg with medications.
(4) Failure: IOP more than 21 mmHg.
SST with Ologen in the first two children was successful, with an IOP of 17 mmHg in the first child (satisfactory success) after 8 months and 11 mmHg in the second child (full success) after 6 months. Corneal clarity improved and its diameter decreased in both cases.
In the third child, the result was 'poor success' with an IOP of 15 mmHg under one medication at 6-months follow-up.
Biodegradable CM (Ologen) can be used in PCG to reduce the surgical risks and complications of SST with mitomycin-C in infants. It is also an easier and safer alternative compared with glaucoma valve implants.
Keywords: Collagen matrix; congenital glaucoma; trabeculectomy
|How to cite this article:|
Hamdi MM. Trabeculectomy assisted by collagen matrix implant (Ologen) in primary congenital glaucoma. J Egypt Ophthalmol Soc 2013;106:188-93
|How to cite this URL:|
Hamdi MM. Trabeculectomy assisted by collagen matrix implant (Ologen) in primary congenital glaucoma. J Egypt Ophthalmol Soc [serial online] 2013 [cited 2018 Dec 15];106:188-93. Available from: http://www.jeos.eg.net/text.asp?2013/106/3/188/127398
| Introduction|| |
Congenital glaucoma is a global problem and poses a diagnostic and therapeutic challenge to the ophthalmologist. Detailed evaluation under general anesthesia (GA) is advisable to establish the diagnosis and plan for its management. Medical therapy has a limited role, and surgery remains the primary therapeutic modality. Although goniotomy or trabeculotomy ab externo is valuable in the management of congenital glaucoma, primary combined trabeculotomy-trabeculectomy offers the best hope for success in advanced cases. Trabeculectomy with antifibrotic agents and using glaucoma drainage devices has a role in the management of refractory cases, and cyclodestructive procedures should be reserved for patients in whom these procedures have failed .
Ologen is an artificial porcine extracellular matrix, which is made of atelocollagen cross-linked with glycosaminoglycan. It is a biodegradable scaffolding matrix that induces a regenerative wound-healing process in the absence of antifibrotic agents. It is designed to prevent episcleral fibrosis and subconjunctival scarring and minimize the random growth of fibroblasts, instead promoting their growth through the pores in the matrix. This implant is found to be biodegradable within 90-180 days . After degradation, the implant leaves behind a loose alignment of collagen fibers inside the bleb, which are remarkably similar to normal tissues .
Two types of Ologen are used in glaucoma surgery, as per the manufacturer's design: the first is a disc of 6 mm diameter × 2 mm thickness [Figure 1]a and the second is a disc of 12 mm diameter × 1 mm thickness [Figure 1]b.
As fibrosis in children is more extensive than in adults, and keeping in mind the complications of antimetabolites in subscleral trabeculectomy (SST) for congenital glaucoma as well as the complications of glaucoma drainage devices, the idea of using collagen matrix (CM) (Ologen) in SST for primary congenital glaucoma (PCG) was considered, with the objective of a more functional bleb postoperatively. This study may be one of the earliest studies to use Ologen in this age group.
| Patients and methods|| |
This study was conducted from January 2012 to December 2012. The primary objective was to evaluate the efficacy and safety of CM (Ologen, Aeon Astron Europe B.V., Leiden, The Netherlands) in PCG surgery, which has a high incidence of failure because of massive subconjunctival bleb fibrosis.
All patients were operated upon after taking informed consent from their parents.
SST was performed with a scleral flap measuring 3 mm × 4 mm, and CM was placed over it. A watertight closure of the conjunctiva with three buried 10.0 nylon stitches was performed. A combination of steroid-antibiotics (dexamethasone-tobramycin) eye drops q.i.d. was prescribed for 6 weeks, tapering over the following 2 weeks.
The parameters evaluated in each patient were: intraocular pressure (IOP), corneal diameter (horizontal), corneal clarity, cup-disc ratio (C/D) if visible, and state of the bleb. The plan was based on evaluation at four follow-up visits under GA at 1 week, 1, 3, and 6 months. GA could be replaced in older cooperative children by performing a slit lamp examination.
IOP was measured using a Schiotz indentation tonometer under GA or a Goldmann applanation tonometer mounted on a slit lamp for older cooperative children. Corneal diameter was measured using a surgical caliper. A photograph was taken to assess the shape, extent, and vascularity of the bleb.
Ultrasound biomicroscopy was planned to be performed during 6 months' follow-up after full absorption of CM to assess the bleb. However, this was not possible because of the difficulty in performing this investigation in such an age group, necessitating GA in the patient.
The definition of success was as follows:
- Full success: IOP less than 15 mmHg without medications; clear cornea.
- Satisfactory success: IOP less than 21 mmHg without medications; clear cornea.
- Poor success: IOP less than 21 mmHg with medications.
- Failure: IOP more than 21 mmHg.
The first case was a 3-year-old child with left PCG.
IOP was 45 mmHg, corneal diameter was 16 mm, corneal clarity was impaired, and fundus was seen with difficulty with a C/D of 0.7. SST with Ologen was performed; the site of the trabeculectomy was direct superiorly and two loose 10.0 nylon stitches were applied for the scleral flap. The Ologen used in this surgery was a disc of 6 mm diameter × 2 mm thickness inserted over the scleral flap under a fornix-based conjunctival flap. The conjunctiva was tightly closed as previously described, and postoperative treatment was prescribed.
At the first-week follow-up visit, IOP was seen to be very soft (4 mmHg), the bleb was elevated and vascularized [Figure 2] and [Figure 3], and conjunctival sutures were removed.
At the 1-month follow-up visit, IOP was seen to be 9 mmHg, corneal diameter was reduced to 13.5 mm, the cornea was clear, C/D was 0.6, and the bleb was still elevated and less vascularized.
The 3-month follow-up was missed, as the child was living far away from Cairo and contact with his parents could not be established.
During the 6-month follow-up visit, 'satisfactory success' was obtained with IOP of 17 mmHg without medications, clear cornea with a diameter of 13 mm, and C/D of 0.5. A diffuse shallow elevated bleb with almost normal vascularization of the conjunctiva was detected [Figure 4].
The second case was a 7-month-old infant with left recurrent PCG. A trabeculotomy-trabeculectomy with mitomycin-C (MMC) was performed at the age of 2 months but failed. Then, a needling was performed twice but failed. Before the second SST was performed in our study, IOP was 30 mmHg on medications (combined dorzolamide-timolol eye drops), epithelial edema of the cornea was observed with impaired clarity, corneal diameter was 13 mm, and C/D was difficult to assess because of poor fundus view.
The scleral flap was temporal in position (away from the first failed bleb). Ologen of the same dimension as in the first case was used and was inserted in the same manner under the conjunctiva. Two loose 10.0 nylon stitches for the scleral flap were applied. The conjunctiva was tightly closed as previously described, and postoperative treatment was prescribed.
At the 1-week follow-up visit, the cornea was seen to be clear with a diameter of 13 mm and IOP was reduced to 10 mmHg. The bleb was elevated and vascularized [Figure 5]. Conjunctival sutures were removed.
At the 1-month follow-up visit, the cornea was clear (except for limited edema close to the new bleb) with a diameter of 13 mm, IOP was 10 mmHg, and C/D was 0.6.
At the 3-month follow-up visit, the same findings were observed (IOP of 10 mmHg, clear cornea with a diameter of 13 mm) except that the bleb was flattened and normally vascularized [Figure 6].
At the 6-month follow-up visit, 'full success' was obtained with IOP of 11 mmHg, clear cornea with reduced diameter of 12.5 mm, and C/D of 0.5. The bleb was diffuse, shallow, and normally vascularized [Figure 7].
The third case was a 7-year-old girl with right recurrent PCG. A previous SST without antifibrotic agents (MMC) was performed at the age of 25 days. IOP was 28 mmHg under medications, which comprised dorzolamide eye drops and a combination of travoprost and timolol. Corneal diameter was 14 mm with impaired corneal clarity due to epithelial edema. C/D was difficult to assess because of poor fundus view.
SST with Ologen was performed. The scleral flap was temporal in position (away from the first failed bleb), and scleral dissection was extremely difficult because of scleral thinning and degeneration. The Ologen used was a disc of 12 mm diameter × 1 mm thickness. One loose 10.0 nylon stitch for the scleral flap was applied. The conjunctiva was tightly closed as previously described, and postoperative treatment was prescribed. On the first postoperative day, the cornea was clear with soft IOP and deep anterior chamber (AC).
At 1-week follow-up, the conjunctival stitches were torn and the CM was exposed. AC was still formed, but IOP was extremely soft, necessitating stitching of the conjunctiva under GA, which was extremely difficult because of friable edematous tissues.
One week later, the conjunctival stitches were torn again, with exposed implant and firm IOP. Massage was prescribed and it resulted in lowering of the IOP. The implant was left in place, allowing for the conjunctival epithelium to cover it. The use of a Goldmann applanation tonometer was difficult at that stage, as the child was uncooperative.
Three weeks later, IOP was 18 mmHg under the same preoperative medications, and CM was epithelialized.
At the 3-month visit, IOP was 18 mmHg under medications, and the parents were advised to perform a massage for the bleb.
Two months later, the patient visited with clear cornea and relatively less elevated bleb. IOP was 15 mmHg without massage and with only one medication, indicating 'poor success'.
During the 6-month follow-up visit, IOP was the same as in the month before [Table 1].
| Discussion|| |
Pediatric glaucoma surgery is challenging because of the difference in child anatomy from that of the adult, differences in the behavior of the tissues of a child's glaucomatous eye, and difficulties with postoperative management. Goniotomy and trabeculotomy are the preferred initial treatments for PCG. Trabeculectomy with adjunctive MMC is more likely to succeed in older patients with phakic glaucoma but carries the long-term risk for bleb-associated endophthalmitis . In addition to affecting DNA, it also affects RNA and protein synthesis. It thereby inhibits fibroblast proliferation and is toxic to endothelial cells. It introduces new complications of its own, including chronic hypotony with maculopathy, cystic avascular blebs, bleb leakage, bleb failure, bleb infections, and endophthalmitis ,.
Glaucoma drainage devices may be preferred in younger children and in patients with aphakic glaucoma, but these devices can cause tube-related complications . These devices create an alternative aqueous pathway by channeling the aqueous chamber from the AC through a long tube, promoting bleb formation .
However, the tube-shunt surgery complications include excessive aqueous outflow, tube obstruction, corneal damage, strabismus, tube migration, and long-term foreign body reaction .
Considering the previous complications, difficulties associated with both antimetabolites and glaucoma drainage devices in PCG surgery, and with the evolution of Ologen in glaucoma surgeries, the idea of applying it underneath the conjunctiva in SST for PCG arose.
Studies in animal models reported that the use of a bioengineered, biodegradable, porous collagen-glycosaminoglycan matrix implant in the subconjunctival space offers an alternative method for controlling the wound-healing process following filtration surgery, avoiding the complications of the administration of antifibrotic agents and offering the potential for maintaining long-term IOP control ,.
The implant offers the potential for a new means of providing controlled resistance between the AC and the subconjunctival space during the early postoperative period, as well as maintaining long-term IOP control by avoiding early scar formation and creating a loosely structured filtering bleb ,.
The preliminary results of the studied cases were 'satisfactory success' for the first case, 'full success' for the second case, and 'poor success' for the third case. These may be considered as promising results for the use of CM Ologen in PCG surgery.
The first case with PCG was not previously operated upon and yielded relative success, whereas the second case was previously operated upon with needling performed twice and yielded 'full success'. The latter information shows that there are many factors affecting the degree of success of using Ologen in PCG, including severity of the disease, presence of previous surgery, IOP lowering medications, and age and race of the patient.
In the third case, long-standing degeneration in the diseased eye played a crucial role in leading to poor success; friable tissues of the cornea and conjunctiva led to torn stitches. Furthermore, the dimension of CM (12 mm × 1 mm) might make the implant slightly corrugated under the conjunctiva, with obstruction of the scleral tunnel that was partially relieved by massaging of the bleb. This was in contrast to the other dimension of Ologen (6 mm × 2 mm) used in the first two cases, which was more regular and uniform. However, in the last follow-up visit 6 months after surgery, IOP improved to 15 mmHg and the height of the bleb was reduced, most probably because of more absorption of the CM relieving the back pressure on the fistula. Nevertheless, this case was graded as 'poor success' because of the use of only one medication. Observing the sequence of events, more success and lowering of IOP is expected with further follow-up.
The advantages of this implant are its safety over MMC and its ease of use. CM (Ologen) would prevent multiple interference such as needling after the use of antifibrotic agents and also would avoid tube-related complications. Furthermore, there was no learning curve comparing with glaucoma drainage devices surgery.
It was advised by the manufacturer to secure the scleral flap of trabeculectomy with a single loose 10.0 stitch in the adult group; even some authors recommended no stitches. However, in the first two cases, two loose 10.0 stitches were applied at the posterior corners of the scleral flap; this is much safer for avoiding any possible postoperative shallowing of the AC. This is difficult to be managed during the early postoperative period in this age group because of the need of an additional GA shortly after surgery, which is not appreciated both in terms of the child's health and by the parents. However, in the third case, one stitch was applied to secure the scleral flap, as the difficulty in scleral dissection led to a small flap. Regardless of the number of stitches used to secure the scleral flap, mild leakage on pressure must be present to ensure ample filtration of aqueous outflow.
The expected bleb with Ologen will be superior to that with MMC in that Ologen will guide healing to be more or less regular in contrast to MMC, which inhibits fibrosis and leads to thin cystic blebs with possible leaks, hypotony, and bleb-related infection and endophthalmitis; this has to be confirmed by ultrasound biomicroscopy in further studies. The conjunctiva over the Ologen is more or less normally vascularized within a few months, which is more healthy than an avascular bleb with MMC.
The use of Ologen in PCG, however, does not preclude the possibility of late-onset infections, such as any case of SST, nor does it cancel a possible postoperative shallow AC. Theoretically, the tamponading effect of the CM implant reduces the possibility of a postoperative leak; this should be monitored with a further large number of cases, keeping in mind that many intraoperative steps can lead to a postoperative shallow AC, such as excision of a large portion of the sclera by the surgical punch, prolonged intraoperative hypotony during surgery, and careless closure of the conjunctiva, which may lead to extrusion of the implant minimizing the tamponading effect, resulting in leak and shallow AC.
In the follow-up visits of the first two studied cases (especially the first case), not only are IOP measurement and corneal clarity important detectors of success but also the reduction in horizontal corneal diameter may be one of the parameters for assessing success of the surgery, especially in younger children with more elastic sclera expected to recoil when IOP is reduced. However, the C/D of the optic disc may be difficult for comparison in preoperative and postoperative states because of the poor view of the fundus before surgery.
This study has some limitations. Recruitment of patients was not easy. It was also difficult to schedule the 3-and 6-month follow-up visits on time as children treated in this work live in distantly located rural areas.
| Conclusion|| |
Biodegradable CM (Ologen) can be used in PCG and can reduce the surgical failure of SST with MMC in infants and children. It can also be an easier and safer alternative than glaucoma valve implants. The use of CM in PCG surgery seems - from the preliminary results within the first 6 months after surgery - to be relatively effective and safe. Further, a large number of cases and longer follow-up are needed to confirm its efficacy and safety.
| Acknowledgements|| |
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]