Intraluminal Stenting Versus External Ligation of Ahmed Glaucoma Valve
Condition: Glaucoma
MeSH terms: Glaucoma
Study type: Interventional

Summary: 
      Objectives: To compare the intraluminal stenting and external ligation of Ahmed Glaucoma
      Valve (AGV) regarding refractory glaucoma management and postoperative hypotony prevention.

      Patients and Methods: This randomized clinical trial included 30 eyes of 25 patients (age
      range: 44-56 y) with refractory glaucoma. This study was conducted during the period from
      September 2018 to January 2020. The study included two groups, AGV with intraluminal stenting
      group (n=15) and AGV with external ligation group (n=15). Follow up continued to a year post
      operation. The primary outcome was Intraocular pressure (IOP) and its association with the
      number of postoperative glaucoma medications. IOP ≤ 21 mmHg without medications announced
      complete success while IOP ≤ 21 mmHg with medications indicated qualified success. IOP of <6
      mmHg defined hypotony.

      Key Words: Stenting- ligation- Ahmed valve- Hypotony
    

Detailed description: 
      Introduction: Refractory glaucoma is a complicated type of glaucoma difficult to be treated.
      This type is characterized by high IOP with a high resistance to be reduced by traditional
      medical or surgical therapy. Shunt surgery improve trabeculectomy poor long term outcomes in
      refractory glaucoma.1 AGV, a shunt device, is used either from the start or after
      conventional procedures failure in refractory glaucoma. It helps the aqueous humour flow
      direct in the silicone tube.2 AGV is effective in reducing the postoperative hypotony
      commonly seen in non valved implants however the presence of persistent hypotony is still a
      problem after AGV.3 Persistent hypotony after AGV is caused by over-priming the tube and
      excessive manipulation of the valve housing that may damage the valve mechanism, the outflow
      of aqueous humour around the silicone tube immediately post-operatorive after the utilization
      of a 22 or 23G needle in creation of the sclerostomy and ciliary body function failure
      post-surgery in complicated eyes in which AGV is used. 4-5 closure of the tube by ligation or
      stenting may be needed when postoperative ocular hypotony occurs. 6 Enough and expected
      outflow control may not be induced by ligation of the tube at a focal area. 7 postoperative
      ocular hypotony could be managed effectively by Ab interno tube stenting. 8-10 Patients and
      Methods: Thirty eyes with refractory glaucoma were included in randomized controlled clinical
      trial. Patients aged from 44 to 56 years old. Despite of tolerated medication after previous
      trabeculectomy surgery, those patients had high intraocular pressure (IOP). Approval of
      institutional research board committee was taken. Two groups were studied; AGV with
      intraluminal stenting group (n=15 eyes) and AGV with external ligation group (n=15 eyes).
      Follow- up to one year after the surgery was done. The primary outcome was Intraocular
      pressure (IOP) and its association with the number of postoperative glaucoma medications. IOP
      ≤ 21 mmHg without medications announced complete success while IOP ≤ 21 mmHg with medications
      indicated qualified success. IOP of <6 mmHg defined hypotony. All patients preoperatively
      were subjected to IOP measurement using Goldman applanation tonometer, visual acuity
      assessment (VA) using Snellen E chart, visual field analysis (VF) by Humphrey visual field
      analyzer, Angle examination by goniolens, optic disc examination by Volk+90 lens, sit lamp
      examination for assessment of corneal clarity and any corneal touch with the tube and
      anterior chamber depth. All patients had peribulbar anaesthesia. Operative technique: in
      group I, incision of superior-temporal conjunctiva was carried out, appropriate cauterization
      and approximately at 10 mm posterior to the corneal limbus, the valve body plate was placed.
      Forceps was used to insert A 7-0 prolene thread into the tube lumen; the prolene 7-0 thread
      was cut with scissors making it along the tube length to remove it when needed. (Figure 2) In
      group II, the same as in group I but 8-0 vicryl was used to ligate the tube with the
      underlying sclera in addition to usage of two interrupted prolene 7-0 sutures applied 2mm
      apart over the tube itself to make partial occlusion and then entered into the anterior
      chamber. (Figure 3) Postoperative treatment with combined antibiotic and steroid eye drops
      every four hours in the first week followed by 2 weeks gradual tapering. IOP, VA, VF, optic
      disc examination by Volk+90 lens, slit lamp examination were the follow-up parameters.
      Failure was considered if the patient needed to implant removal, added glaucoma surgery, or
      developed phthisis bulbi.

      Statistical analysis: Data were statistically analyzed by SPSS version 22(SPSS Inc., Chicago,
      IL, USA). Non-paired t test and Mann-Whitney were applied to quantitative variables. Fisher's
      exact test was applied to qualitative variables. Correlation was used to assess strength and
      direction of association. Less than 0.05 P value was set to be significant.

      Data Availability Statement:The data used to support the findings of this study are included
      within the article.

      Compliance with Ethical Standards Funding Statement: None Conflicts of Interest: The author
      declares that there he has no conflict of interest regarding the publication of this paper.

      Ethical approval: All procedures performed in studies involving human participants were in
      accordance with the ethical standards of the institutional committee and with the 1964
      Helsinki declaration and its later amendments or comparable ethical standards.

      Informed consent: Informed consent was obtained from all individual participants included in
      the study.
    

Intervention name(s): Ahmed Glaucoma Valve
Intervention type(s): Device
Intervention description(s): To compare the prevalence of postoperative hypotony between the 2 arms
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: : This randomized clinical trial included 30 eyes of 25 patients (age range: 44-56 y) with refractory glaucoma. This study was conducted during the period from September 2018 to January 2020. The study included two groups, AGV with intraluminal stenting group (n=15) and AGV with external ligation group (n=15). Follow up continued to a year post operation. The primary outcome was Intraocular pressure (IOP) and its association with the number of postoperative glaucoma medications. IOP ≤ 21 mmHg without medications announced complete success while IOP ≤ 21 mmHg with medications indicated qualified success. IOP of <6 mmHg defined hypotony.
Masking: None (Open Label)
Primary purpose: Treatment