Outcome of Gonioscopy-Assisted Transluminal Trabeculotomy (GATT) across the spectrum of childhood glaucoma.

DETAILS OF THE RESEARCH PROJECT

1.      TITLEOF THE RESEARCH PROJECT: Outcome ofGonioscopy-Assisted Transluminal Trabeculotomy (GATT) acrossthe spectrum of childhood glaucoma

2. BACKGROUND:

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

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

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

3. RESEARCHQUERY: Will GATT beable to reliably control IOP and progression of Glaucoma in children with Glaucoma?

4.      AIMSAND OBJECTIVES:

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

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

 5.      REVIEWOF LITERATURE:

Gonioscopy-assistedtransluminal trabeculotomy (GATT) is a sutureless, blebless ab interno trabeculotomyapproach introduced at the Glaucoma Associates of Texas (Dallas, TX) by Groverand colleagues.3 Thetechnique described by Grover and colleagues involves the creation of nasalgoniotomy of 1-2 clock hours with a 25G microvitreoretinal (MVR) blade via the temporalside port. The trabecular meshwork (TM) is bisected. Either suture or themicrocatheter (iTRACK, Ellex iScience Inc., Fremont, CA) is directed behind theTM 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 thesurgeon along the Schlemm’s canal via a pushing forward technique. Once the microcatheteror suture goes 360 degrees, it is pulled out, allowing a cutting motion to bisectthe trabecular meshwork.

Trabeculotomy with McPhersonor Harms trabeculotomy probes generally yields suboptimal long-term results.6 This is because one cantreat only superior 120 -150 degrees using Harms trabeculotome. However, overthe past decade, progress in technique and technology has led to theintroduction of circumferential trabeculotomy. Studies in the adult populationhave shown increased success and efficacy; for example, Chin et al. found that360 suture trabeculotomy ab externo was significantly more effective inlowering IOP in adult primary and secondary glaucomas than metal trabeculotomy.6 The higher success ratewith 360 modern-day circumferential trabeculotomy is likely because of greateraccess to more collector channels and improved cleavage of the trabecularmeshwork.

Previous studies have shownbetter success rates with 360-degree ab externo circumferential trabeculotomy thangoniotomy7, 8 or metaltrabeculotomy.9 Severalauthors have highlighted the advantages of treating the entire 360 degrees ofTM in one procedure, thereby maximizing IOP reduction and minimizing the risksof multiple anesthesias.7,8  Mendicino et al.7 compared 360-degree trabeculotomy to goniotomy in asix-year study. They found better visual outcomes and IOP reduction in the360-degree treatment group. Grover et al., in 2015, reported greater successwith gonioscopy assisted transluminal trabeculotomy (GATT) when performed by foursurgeons at four sites in 14 eyes of 10 patients with PCG or juvenile open-angleGlaucoma (JOAG).10 Theyreported 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 theefficacy of the technique as an isolated procedure in pediatric glaucoma. Asthis ab interno procedure is still novel, this study aims to assess itsefficacy and safety and review factors that might affect the outcome of GATT inchildren with Glaucoma

6. Preliminarywork - Preliminary hasalready been done by the Investigator on this project where they didrestrospective study of the glaucoma patients who underwent GATT in last oneyear. Total 20 eyes underwent GATT, 17 were from the pediatric age group, andthree were adults. Only three patients who had a minimum of one year of follow-uphad surgical failure. There was also significant reduction in IOP and the numberof anti-glaucoma medications in the post-operative period. Hyphema was the mostcommon post-operative complication which was self-resolving in all cases.Choroidal detachment, retinal detachment, and corneal infiltrates were a fewother complications. So, GATT appears to be a safe and effective surgical toolto control IOP and reduce anti-glaucoma medications.

7 DETAILEDRESEARCH METHODOLOGY**:**

**Study type:**Ambispective (prospective and retrospective), non-randomized, interventionalstudy

Studysetting: Advanced Eye Centre, PGIMER, Chandigarh

Participants-

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

Inclusion criteria:

1. A diagnosedcase of childhood glaucoma according to CGRN classification requiring glaucomasurgery

2. Cornea clearenough to visualize angle structures

Exclusion criteria:

1. Patients who have undergone previoussurgery for Glaucoma.

Preoperativeassessment

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

Surgicalprocedure

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

Postoperativeassessment

Postoperative datawill be collected from 1 day, 1 week, 1 month, 3 months, and 6 months, ifavailable, to assess the results of the GATT surgery. Intraocular pressure(IOP) will be measured by Perkins tonometer or iCare tonometer, slit-lampbio-microscopy, gonioscopy, stereoscopic fundus evaluation on the slit lampusing a 90.0-D lens or with indirect ophthalmoscope using a 20.0 D lens or withgonioscopy lens under an operating microscope, axial length using ultrasoundA-scan or optical biometry, cornea clarity grading, and central cornealthickness will be measured. The number of glaucoma medications, if any, requiredfor IOP control will be noted.

Outcome measures:

Primary:

·        The decrease inintraocular pressure

·        The decrease inantiglaucoma medications

Secondary:

·        Improvement in visualacuity

·        Complications of surgery

·        Secondary interventionsrequired

·        Improvement in corneaclarity

·        Decrease in cornealthickness

Successcriteria:

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

Qualifiedsuccess- IOP≤ 18 mmHg with up to 2 antiglaucoma medicines

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

8STATISTICAL ANALYSIS:

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