|Year : 2016 | Volume
| Issue : 1 | Page : 24-28
A comparative study between trabeculotomy with deroofing of Schlemm's canal augmented with Ologen implant and conventional trabeculotomy in primary congenital glaucoma
Mohamed A.H. Elmallah MSc., MD., PhD. 1, Thanaa H Mohamed2, Ahmed G Elmahdy1
1 Department of Ophthalmology, Faculty of Medicine, Al-Azhar University, Cairo, Egypt
2 Department of Ophthalmology, Faculty of Medicine, Ain Shams University, Cairo, Egypt
|Date of Submission||30-May-2015|
|Date of Acceptance||12-Aug-2015|
|Date of Web Publication||16-Mar-2016|
Mohamed A.H. Elmallah
Prof of Ophthalmology, Al-Azhar Univesity, Cairo, Egypt, Fellow of Regensburg University Hospital Germany Eye Consultant at International Eye Hospital, Roxy, Cairo Member of ESCRS, EOS, IGS and EGS, 11326 Cairo
Source of Support: None, Conflict of Interest: None
The aim of the study was to evaluate the efficacy and safety of Schlemm's canal deroofing augmented by Ologen to enhance the success of trabeculotomy for primary congenital glaucoma (PCG).
Patients and methods
Thirty-two eyes of 21 patients were included in this prospective study, classified into two equal groups: the study group and the control group. The study group underwent trabeculotomy with Schlemm's canal deroofing and subconjunctival Ologen implantation, and the control group underwent trabeculotomy alone for infants affected by PCG. The participants were followed up for 6 months.
According to the definitions for success, qualified success, and failure, the study group had 13/16 (81.25%) cases of success and 3/16 (18.75%) cases of qualified success. The control group reported 10/16 cases (62.50%) of success, 2/16 cases (12.50%) of qualified success, and 4/16 cases (25%) of failure.
Success and qualified success were higher in the study group (trabeculotomy augmented with deroofing of Schlemm's canal and Ologen implant) than in the control group after 6 months of follow-up for cases of PCG.
Keywords: Ologen, primary congenital glaucoma, Schlemm′s canal, trabeculotomy
|How to cite this article:|
Elmallah MA, Mohamed TH, Elmahdy AG. A comparative study between trabeculotomy with deroofing of Schlemm's canal augmented with Ologen implant and conventional trabeculotomy in primary congenital glaucoma. Delta J Ophthalmol 2016;17:24-8
|How to cite this URL:|
Elmallah MA, Mohamed TH, Elmahdy AG. A comparative study between trabeculotomy with deroofing of Schlemm's canal augmented with Ologen implant and conventional trabeculotomy in primary congenital glaucoma. Delta J Ophthalmol [serial online] 2016 [cited 2020 May 31];17:24-8. Available from: http://www.djo.eg.net/text.asp?2016/17/1/24/178764
| Introduction|| |
Primary congenital glaucoma (PCG) refers to a specific form of developmental glaucoma characterized by an isolated maldevelopment of the trabecular meshwork 'isolated trabeculodysgenesis' not associated with other developmental ocular anomalies or ocular disease that can raise the intraocular pressure (IOP). It is also called primary infantile glaucoma and is mostly bilateral, but 25% of cases may be unilateral .
A detailed evaluation of congenital glaucoma under general anesthesia is advisable to diagnose and plan the management. Medical therapy has a limited role, and surgery remains the primary therapeutic modality .
Several studies have reported that trabeculotomy as an initial procedure has a higher success rate compared with goniotomy, but some other studies have shown that they are equally effective ,,.
The reported success rates of goniotomy and trabeculotomy ab externo are similar, ranging from 78 to 93.4% ,,.
The procedure entails 'deroofing' Schlemm's canal to facilitate the drainage of aqueous without penetrating the eye. This is done by exposing the canal after partial-thickness sclerectomy and keratotomy along a 5-mm arc .
Ologen is a biodegradable, bioengineered, porous collagen-glycosaminoglycan matrix made up of 1% collagen/C-6-S copolymer (OculusGen Biomedical Inc., Taipei, Taiwan). Its implantation in the subconjunctival space offers an alternative method for controlling the wound-healing process following glaucoma filtration surgery. Ologen helps in avoiding the complications of antimetabolites and offers the potential for maintaining long-term IOP control ,,.
| Patients and methods|| |
Informed consent was taken from parents after explanation of the procedure. Ethical committee approval from the Faculty of Medicine, Al-Azhar University, was obtained.
In this prospective study, 21 patients (32 eyes), nine male and 12 female patients, who presented with PCG were included. The ages of the children in the study group ranged between 2 and 9 months (mean age = 5 ± 1.75 months) and the age of the control children ranged between 2 and 10 months (mean age = 6 ± 2.05 months). IOP was measured in all eyes preoperatively; it ranged from 22 to 34 mmHg. The mean IOP was 28.5 ± 3.2 mmHg in the study group and 27 ± 3.16 mmHg in the control group [Table 1].
All patients underwent clinical assessment under light general anesthesia in the form of corneal diameters (vertical and horizontal), clarity of the cornea, anterior segment examination, IOP, gonioscopy, indirect fundus examination, and ultrasound biomicroscopy to exclude secondary buphthalmos [Figure 1].
Under general anesthesia and before intubation, IOP was measured using a Perkins tonometer. Vertical and horizontal corneal diameters were measured. Gonioscopy was performed using Swan-Jacob handled lens for assessment of the angle and to exclude any congenital syndromes. Then a corneal traction suture at 12 o'clock was applied to explore a wide view.
The procedure of trabeculotomy with deroofing of Schlemm's canal essentially involves creation of a fornix-based conjunctival flap, creation of a 3 × 3.5 mm rectangular superficial scleral flap. Deroofing the Schlemm's canal was done by incising at the junction of the bluish-gray zone anteriorly and the white scleral zone posteriorly. A small vertical incision on one side of the area under the created scleral flap was made to identify Schlemm's canal. Then using forceps or colibri we removed the thin membrane (outer wall roof) of Schlemm's canal [Figure 2].
After that, the metal trabeculotome was introduced on each side and entered into the anterior chamber, followed by suturing the scleral flap with 10/0 nylon and the conjunctiva with 8/0 vicryl. In the study group an Ologen implant that was 1/2 of the original disc [Figure 3] was applied under the conjunctiva, near the edge of the scleral flap, to suck out any aqueous oozing from the Schlemm's canal. In the control group the same procedure was carried out without deroofing the Schlemm's canal or applying Ologen implant. All surgeries were conducted by one surgeon, with the same technique for each group.
|Figure 3: Half disc of Ologen during implantation in the subconjunctival space at the end of the trabeculotomy.|
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The success of surgery depends mainly on identification of the Schlemm's canal and passage of the metal probe through the canal correctly.
A primary outcome measure was success as defined by the following criteria: complete success was defined as IOP less than 18 mmHg under general anesthesia, no progression of corneal diameter, improvement of corneal edema, and reversibility of cupping. Qualified success was defined as maintenance of such pressure with a single topical antiglaucoma medication. Failure was defined as IOP greater than 18 mmHg under general anesthesia despite topical medications or if the patient required additional surgery.
At the end of the follow-up visits, data of all eyes were analyzed, as seen in [Table 2].
|Table 2: Comparison between both groups regarding the preoperative and postoperative intraocular pressure (mmHg)|
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Data were collected and analyzed using the Statistical Package for Social Sciences (SPSS) for Windows, version 20.0 (IBM Corp., Armonk, New York, USA). The following tests were carried out: the Student t-test was used to search for any significant difference between the two groups and the paired sample t-test of significance was used when comparing between related samples included in this study.
Follow-up was done for all eyes for 6 months as follows: on the first postoperative day, at 2 weeks, and at 1, 3, and 6 months. IOP measurements under light general anesthesia were taken at 1, 3, and 6 months' follow-up visits, but the corneal diameter was assessed in the last follow-up visit only.
| Results|| |
In this study, 32 eyes of 21 patients were operated upon by trabeculotomy, which was modified by deroofing of Schlemm's canal and subconjunctival implantation of Ologen in 16 eyes (study group) and compared with a control group that was treated with conventional trabeculotomy.
No statistically significant difference was found between the study group and the control group regarding age and sex, but there was a statistically significant difference (P = 0.037) in corneal diameter between the two groups [Table 1].
No major complications were seen, except transient hyphema in nearly 50% of cases (8/16 eyes) in the study group and 37.5% (6/16) in the control group, which disappeared after 3–5 days and false passage in one eye (6.25%) in the nasal side only in the control group.
No significant difference was found between the two groups as regards the IOP in the first month postoperatively. There was a highly statistically significant difference (P < 0.001) between the two groups as regards the IOP at the third and sixth month postoperatively [Table 2].
As regards corneal diameter there was no statistically significant difference (P = 0.407) between preoperative and postoperative measurements [Table 3].
|Table 3: Paired difference between preoperative and postoperative corneal diameter in the study and control groups|
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Trabeculotomy with deroofing was successful in all 16 eyes by the end of follow-up with complete success in 13/16 eyes (81.25%) and qualified success in 3/16 (18.75%), whereas trabeculotomy alone was successful in 12 out of 16 eyes (75%) with complete success in 10 eyes (62.5%) and qualified success in two eyes (12.5%) and failure in four eyes (25%). Combined trabeculotomy-trabeculectomy was carried out with mitomycin-c for these failed cases.
| Discussion|| |
The deroofing of Schlemm's canal was described previously by Welsh et al. in 1998 , as they had performed it in patients with open-angle glaucoma with implantation of a glaucoma drainage device. The authors of that study, with its high success rate, had indicated their intention to introduce the same technique in PCG with Ologen implantation. In the present study, after follow-up for 6 months, a good success rate was achieved 81.25% complete success and 18.75% qualified success and no failures.
Nonpenetrating procedures are of particular interest in pediatric patients because they are assumed to have a decreased risk for hypotony, infection, lens injury, Descemet's detachment, and other intraocular trauma. Deep sclerectomy involves the unroofing of Schlemm's canal under a scleral flap, with concurrent removal of the juxtacanalicular trabecular tissues without entering the eye. The procedure leaves behind a trabeculodescemetic window that provides resistance to aqueous drainage to prevent hypotony .
Al-Obeidan et al.  prospectively followed up 143 eyes of 120 patients with congenital glaucoma without concurrent anterior segment anomalies (90.9% were diagnosed with PCG). Within the group in which nonpenetrating deep sclerectomy was performed, success (IOP under 21 mmHg) after mean follow-up of 35.8 months was 82.4% (79.9% complete success, 2.7% qualified success). In our study the complete success rate was 81.25% and qualified success was 18.75% in the study group. We did not have any failed case. Combining the deroofing of Schlemm's canal with trabeculotomy may improve our results but follow-up of 6 months is too short a period to deduce any definitive conclusion on this issue.
Trabeculotomy involves disrupting the tissue between Schlemm's canal and the anterior chamber using an ab-externo approach to create a direct communication. Currently, there are at least three different approaches: rigid probe, suture, and illuminated microcatheter. High success rates ranging from 87 to 92% in cases of PCG presenting before 1 year of age make trabeculotomy an excellent procedure . In our study we had complete success in 62.50% and qualified success in 12.50%; failure was detected in four eyes (25%) in the trabeculotomy group. The lower success rate in our study may be due to the smaller number of cases.
Autrata and Lokaj  have reported that 34 (89.1%) of 38 eyes after trabeculotomy had controlled IOP on the last visit. All eyes were treated by a single procedure, and 17 (44.7%) eyes required antiglaucoma medication to maintain pressure control. Successful IOP control was achieved by one operation in 29 (76%) of 38 eyes after trabeculotomy.
Also, Toykuliev et al.  have reported that a good control of IOP was achieved in 80.39% of patients after trabeculotomy 2 years postoperatively.
Debnath et al.  revealed a 1-year success rate of 67% for trabeculotomy.
The IOP last visit postoperatively was lower in the study group than in the control group by nearly 5 mmHg. There was no significant difference between the two groups as regards IOP in the first month postoperatively. IOP was statistically lower in the study group by the third and sixth month postoperatively, compared with the control group.
There were no serious intraoperative or postoperative complications like shallow anterior chamber, retinal detachment, choroidal detachment, or hemorrhage in any patient over the follow-up period.
Hyphema was noted in 37.5-50% of cases, which was comparable to the 50% incidence of hyphema after trabeculotomy reported by McPherson and McFarland . All of the hyphemas were trivial and resolved quickly.
In the study group, Ologen implantation improved the success rate, with no failed cases until the end of the follow-up period. It also reduced the incidence of shallow anterior chamber postoperatively.
| Conclusion|| |
Trabeculotomy augmented with deroofing of Schlemm's canal and Ologen implant has a more favorable outcome in terms of IOP-lowering efficacy and success rate compared with trabeculotomy alone. However large-scale, long-term, and well-designed randomized controlled trials are needed.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3]