DETAILS OF THE RESEARCH PROJECT

1.      TITLE OF THE RESEARCH PROJECT: Outcome of Gonioscopy-Assisted Transluminal Trabeculotomy (GATT) across the spectrum of childhood glaucoma

2.      BACKGROUND:

The treatment of childhood glaucoma is mainly surgical. Trabeculotomy alone or a combination of trabeculectomy has been practiced for decades. Historically, it has shown high rates of success for pediatric Glaucoma. It lowers IOP by increasing the outflow through Schlemm’s canal and the collector channels. Traditionally, the ab externo approach is practiced for trabeculotomy; however, the advent of technology and the need for new surgical methods have gradually shifted attention from ab externo to ab interno procedures. The success of ab externo trabeculotomy is well documented in the literature, but few reports on the efficacy and safety of ab interno trabeculotomy.

GATT is a newly-developed ab interno trabeculotomy approach introduced by Grover and colleagues.³ It has shown success in decreasing both IOP and the number of antiglaucoma medications in adult glaucoma patients.⁴ Few Case series have also shown that GATT is effective and safe surgery for treating childhood glaucomas also, especially in PCG patients.⁵

The present study aims to study the efficacy and safety of Gonioscopy-Assisted Transluminal Trabeculotomy (GATT) in patients with childhood glaucoma.

3.      RESEARCH QUERY: Will GATT be able to reliably control IOP and progression of Glaucoma in children with Glaucoma?

4.      AIMS AND OBJECTIVES:

·         Primary objective: To evaluate the efficacy and safety of Gonioscopy-Assisted Transluminal Trabeculotomy (GATT) across the spectrum of childhood glaucoma.

·         Secondary Objective: Which entity of childhood glaucoma is most amenable to GATT.

5.      REVIEW OF LITERATURE:

Gonioscopy-assisted transluminal trabeculotomy (GATT) is a sutureless, blebless ab interno trabeculotomy approach introduced at the Glaucoma Associates of Texas (Dallas, TX) by Grover and colleagues.³ The technique described by Grover and colleagues involves the creation of nasal goniotomy of 1-2 clock hours with a 25G microvitreoretinal (MVR) blade via the temporal side port. The trabecular meshwork (TM) is bisected. Either suture or the microcatheter (iTRACK, Ellex iScience Inc., Fremont, CA) is directed behind the TM into Schlemm’s canal using intraocular micro forceps through a 1.2mm nasal paracentesis. This is followed by careful advancement of the microcatheter or suture by the surgeon along the Schlemm’s canal via a pushing forward technique. Once the microcatheter or suture goes 360 degrees, it is pulled out, allowing a cutting motion to bisect the trabecular meshwork.

Trabeculotomy with McPherson or Harms trabeculotomy probes generally yields suboptimal long-term results.⁶ This is because one can treat only superior 120 -150 degrees using Harms trabeculotome. However, over the past decade, progress in technique and technology has led to the introduction of circumferential trabeculotomy. Studies in the adult population have shown increased success and efficacy; for example, Chin et al. found that 360 suture trabeculotomy ab externo was significantly more effective in lowering IOP in adult primary and secondary glaucomas than metal trabeculotomy.⁶ The higher success rate with 360 modern-day circumferential trabeculotomy is likely because of greater access to more collector channels and improved cleavage of the trabecular meshwork.

Previous studies have shown better success rates with 360-degree ab externo circumferential trabeculotomy than goniotomy^{7, 8} or metal trabeculotomy.⁹ Several authors have highlighted the advantages of treating the entire 360 degrees of TM in one procedure, thereby maximizing IOP reduction and minimizing the risks of multiple anesthesias.^7,8  Mendicino et al.⁷ compared 360-degree trabeculotomy to goniotomy in a six-year study. They found better visual outcomes and IOP reduction in the 360-degree treatment group. Grover et al., in 2015, reported greater success with gonioscopy assisted transluminal trabeculotomy (GATT) when performed by four surgeons at four sites in 14 eyes of 10 patients with PCG or juvenile open-angle Glaucoma (JOAG).¹⁰ They reported that mean intraocular pressure (IOP) decreased from 27.3 to 14.8 mm Hg, and the mean number of medications decreased from 2.6 to 0.86.  There have been no studies evaluating the efficacy of the technique as an isolated procedure in pediatric glaucoma. As this ab interno procedure is still novel, this study aims to assess its efficacy and safety and review factors that might affect the outcome of GATT in children with Glaucoma 

6. Preliminary work - Preliminary has already been done by the Investigator on this project where they did restrospective study of the glaucoma patients who underwent GATT in last one year. Total 20 eyes underwent GATT, 17 were from the pediatric age group, and three were adults. Only three patients who had a minimum of one year of follow-up had surgical failure. There was also significant reduction in IOP and the number of anti-glaucoma medications in the post-operative period. Hyphema was the most common post-operative complication which was self-resolving in all cases. Choroidal detachment, retinal detachment, and corneal infiltrates were a few other complications. So, GATT appears to be a safe and effective surgical tool to control IOP and reduce anti-glaucoma medications.

7 DETAILED RESEARCH METHODOLOGY:

Study type: Ambispective (prospective and retrospective), non-randomized, interventional study

Study setting: Advanced Eye Centre, PGIMER, Chandigarh

Participants -

All patients diagnosed with childhood glaucoma, according to CGRN classification, with eyes amenable to glaucoma surgery with cornea clear enough to visualize angle structures of either sex will be included. Patients who underwent GATT from January 2021 to June 2022 will be included. Outcomes will be analyzed at 6-months and one-year post-surgery.

Inclusion criteria:

1. A diagnosed case of childhood glaucoma according to CGRN classification requiring glaucoma surgery

2. Cornea clear enough to visualize angle structures

Exclusion criteria:

1. Patients who have undergone previous surgery for Glaucoma.

Preoperative assessment

Basic demographic information such as age, and gender will be documented and the number and types of glaucoma medications. Details of the preoperative ophthalmic examination will be noted, including best-corrected visual acuity (BCVA) testing using Logmar scale, intraocular pressure (IOP) measured by Goldmann applanation tonometer or Perkins tonometer or iCare tonometer, slit-lamp bio-microscopy, gonioscopy, stereoscopic fundus evaluation on the slit lamp using a 90.0-D lens or with indirect ophthalmoscope using a 20.0 D lens or with gonioscopy lens under an operating microscope, axial length using ultrasound A-scan or optical biometry, cornea clarity grading, and central corneal thickness measurement. 

Surgical procedure

All surgery will be performed by a single surgeon. All surgery will be performed using a temporal approach to treat 360-degree angles using a 5-0 prolene suture.

Postoperative assessment

Postoperative data will be collected from 1 day, 1 week, 1 month, 3 months, and 6 months, if available, to assess the results of the GATT surgery. Intraocular pressure (IOP) will be measured by Perkins tonometer or iCare tonometer, slit-lamp bio-microscopy, gonioscopy, stereoscopic fundus evaluation on the slit lamp using a 90.0-D lens or with indirect ophthalmoscope using a 20.0 D lens or with gonioscopy lens under an operating microscope, axial length using ultrasound A-scan or optical biometry, cornea clarity grading, and central corneal thickness will be measured. The number of glaucoma medications, if any, required for IOP control will be noted.

Outcome measures:

Primary:

·         The decrease in intraocular pressure

·         The decrease in antiglaucoma medications

Secondary:

·         Improvement in visual acuity

·         Complications of surgery

·         Secondary interventions required

·         Improvement in cornea clarity

·         Decrease in corneal thickness

Success criteria:

Complete success- IOP ≤ 18 mmHg after surgery without any antiglaucoma medicines.

Qualified success- IOP ≤ 18 mmHg with up to 2 antiglaucoma medicines

Failure- IOP was >18 mmHg on two topical drugs or need for systemic drugs for IOP control or requirement of re-surgery.

 8 STATISTICAL ANALYSIS:

Statistical analysis will be performed using SPSS software. The continuous variable will be presented in mean + standard deviation (SD) and categorical variables will be presented as frequencies, and percentages. We will use paired t-test to evaluate the differences between continuous variables. Notably, a p value ≤0.05 will be considered statistically significant. A p-value <0.05 will be considered statistically significant.