Efficacy and Safety of ab Interno Trabeculectomy With the Kahook Dual Blade
Condition: Glaucoma, Open-Angle; Ocular Hypertension; Eye Diseases; Hypertension; Intraocular Pressure; Cataract
MeSH terms: Glaucoma; Cataract; Eye Diseases; Ocular Hypertension; Glaucoma, Open-Angle; Hypertension
Study type: Interventional

Summary: 
      The Kahook Dual Blade is a single-use device specially designed to create a clean cut in the
      trabecular meshwork. This ablation in the trabecular meshwork allows a better outflow of the
      aqueous humor, thus reducing the intraocular pressure (IOP), theoretically beyond the IOP
      reduction achieved by other minimally invasive glaucoma surgery (MIGS) devices.

      Studies already published showed good results in terms of the reduction of the number of
      glaucoma medications and the reduction in the IOP, but not a single study has been performed
      prospectively comparing the efficacy of the technique, not even with the cataract surgery.
    

Detailed description: 
      This new device, the Kahook Dual Blade, has been specially designed to create a gentle cut
      compared to other cutting-devices that also remove the trabecular meshwork. Preclinical
      investigation showed no harm in the surrounding tissues. Only two prospective studies have
      been published, showing good results in terms of IOP reduction and a significant cut-off in
      the glaucoma medications. However, to better assess the real effect, a prospective comparison
      with cataract surgery or any other trabecular technique should be performed. We also aimed to
      determine the safety of the procedure.

      Study design A prospective, randomized controlled, interventional study was conducted to
      determine the efficacy and safety of the Kahook Dual Blade. Patients with cataract and
      open-angle glaucoma or ocular hypertension (OHT) were included.

      Subjects Patients were consecutively recruited from the Department of Glaucoma. Eligible
      patients were asked to participate if cataract surgery was indicated due to best-corrected
      visual acuity (BCVA) bellow 0.5 (in decimal scale), and moderate IOP reduction and a cut-off
      of the glaucoma medications was also aimed. Patients included in the study had been
      previously diagnosed with primary open-angle (POAG), pseudoexfoliative glaucoma (PSX) or OHT,
      and mild-to-moderate glaucoma according to the Hodapp-Parrish-Anderson classification,
      preoperative IOP ≤ 24 mmHg on at least one hypotensive medication, and coexistence of
      cataract without narrowing the angle (visible scleral spur at least in 2 quadrants). Both
      eyes from the same patient could be eligible if they both met the inclusion criteria.

      Subjects who did not fulfill the inclusion criteria were excluded: patients with other
      glaucoma subtypes (elevated episcleral venous pressure, orbital occupancy, Sturge-Weber
      syndrome or any type of angle-closure glaucoma). Patients who underwent any intraocular
      surgery in the previous six months, including any laser or surgical intervention for
      glaucoma, or patients with any ophthalmic diseases that may interfere with tests were
      excluded. Severe or end-stage glaucoma or those with an indication of filtering or glaucoma
      drainage implant surgeries due to a high IOP with the maximum tolerated medication or
      glaucoma progression were also exclude.

      All subjects were thoroughly examined before clinical intervention. This included a medical
      history review, slit-lamp examination, IOP determination with hand-held applanation
      tonometer, gonioscopy, dilated fundus examination, endothelial cell count (ECC) including
      cell and size automated detection with specular microscopy (EM-3000, Tomey Corporation,
      Nagoya, Japan), simulated keratometry (simK) determined by topography (Pentacam®, Oculus,
      Wetzlar, Germany), and standard automated perimetry (VF) (G1-Tendency Oriented Perimeter,
      Octopus® 1-2-3, Haag-Streit, USA).

      Assignation and surgical technique For safety reasons, patients did not discontinue any
      topical hypotensive medications before surgery.

      A randomized, controlled study was designed. Eyes were randomly assigned to each treatment
      group (www.random.org). If both eyes of the same patient were eligible to participate in the
      study, they could be allocated in different treatment groups due to randomization. All
      surgeries were performed by two experienced glaucoma surgeons. Standard cataract surgery with
      phacoemulsification using a 1.8 mm clear corneal incision (CCI) and intraocular lens (IOL)
      capsular bag placement was performed under topical anesthesia and 1% intracameral lidocaine.
      The surgeons were blinded to randomization until the end of the cataract surgery. At this
      point, if the patient was assigned to the treatment group the surgeon instilled acetylcholine
      1% to reduce the pupillary size and facilitate visualization of the angle structures. To help
      maintain width, the anterior chamber was filled with a viscoelastic agent. Since the ab
      interno trabeculectomy is performed in the nasal quadrant, the surgeons then situated
      temporal, the patient's head was rotated 45 degrees in the opposite direction of the surgical
      site, and the microscope was tilted 30 to 45 degrees towards the surgeon. To guarantee better
      access to the nasal area of the angle, a 1.8 mm keratome was employed to widen the
      paracentesis. Further details of the surgical technique are described elsewhere.

      Postoperative medications and follow-up Hypotensive medication was not administered intra- or
      post-operatively unless an IOP spike was detected. Postoperative topical treatment included a
      fixed combination of antibiotic plus steroid (tobramycin 0.3% and dexamethasone 0.1%) six
      times a day for seven days; this was tapered over the next four weeks.

      Visits were undertaken at 1 day, 1 week, 1 month, 2 months, 3 months, 6 months, and 12
      months. During follow-up, results of the slit-lamp examination, applanation tonometer IOP,
      and the number of medications were recorded at all visits. The VF and the ECC were also
      re-tested at 6 and 12 months. All the postoperative visits were conducted by the same
      examiner (NVA). Topical glaucoma medication was re-introduced if the target IOP according to
      the severity of the visual field was not achieved, o a higher than preoperative IOP was
      found.

      Outcome measures - Data analysis Data obtained from each group were evaluated to determine
      the efficacy and safety of both interventions. The primary study outcomes were IOP and the
      number of glaucoma treatments. VF, ECC, BCVA and simK were secondary outcomes used to define
      the safety of both procedures. Success was defined as an IOP reduction of ≥ 20% from
      baseline; this cut-off was based on that reported in other glaucoma surgeries and is used for
      evaluation of this trabecular technique. The Saphiro-Wilk test was used to assess the sample
      distribution. Independent and dependent sample t-tests, when possible, were used to compare
      the results between groups and over time for each group. As both eyes of the same patient
      could be included in any of the treatment groups, generalized estimating equations (GEE) for
      repeated measures (IOP and number of medications) were also performed. A random-effect
      logistic regression was employed to analyse baseline characteristics associated with the
      success endpoint (IOP reduction of ≥20% from baseline). Statistical significance was set at a
      two-sided p-value ≤ 0.05. Statistical analyses were performed using Stata® version 14.1
      (StataCorp, College Station, Texas, USA).
    

Intervention name(s): Ab interno trabeculectomy; Cataract
Intervention type(s): Procedure; Procedure
Intervention description(s): Ab interno trabeculectomy performed after pupil contraction and 90 degrees ablation of the nasal trabecular meshwork; Cataract surgery with minimal clear cornea incision and phacoemulsification
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: One group received combined surgery, while the other cataract surgery alone
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Glaucoma; Ocular hypertension; Glaucoma, Open-Angle; Ab interno trabeculectomy; Phacoemulsification; Combined surgery; Minimally Invasive Glaucoma Surgery