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 Table of Contents  
Year : 2022  |  Volume : 2  |  Issue : 4  |  Page : 891-893

Gonioscopy-assisted transluminal trabeculotomy (GATT) in Indian eyes – A description of 1-year follow-up results of the GATT procedure in a series of patients with open-angle glaucoma in South India

Department of Glaucoma, Aravind Eye Hospital, Coimbatore, Tamil Nadu, India

Date of Submission16-Apr-2022
Date of Acceptance24-Jun-2022
Date of Web Publication11-Oct-2022

Correspondence Address:
Dr. Ganesh Venkataraman
Glaucoma Clinic, Aravind Eye Hospital, Avinashi Road, Coimbatore - 641 014, Tamil Nadu
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijo.IJO_947_22

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Trabeculectomy is considered as the gold standard for surgical treatment of glaucoma. The use of conjunctiva to create a filtering bleb limits future surgical options. Gonioscopy-assisted transluminal trabeculotomy (GATT) is an ab interno trabeculotomy technique that has the advantage of reducing the intra-ocular pressure (IOP) in a conjunctiva sparing manner. Ten eyes of eight patients underwent GATT and were followed up for a minimum period of 6 months. Eight eyes were not on any glaucoma medication till the end of their last follow-up, which ranged from 6 months to 1 year. Two eyes were advised to undergo additional glaucoma surgery. All eyes except one retained their visual acuity in the post-operative follow-up period. GATT is a promising technique for the treatment of mild to advanced open-angle glaucoma with an added benefit of sparing the conjunctiva for future interventions.

Keywords: GATT, juvenile open-angle glaucoma, secondary open-angle glaucoma

How to cite this article:
Venkataraman G, Manju M, Chandran P, Dhavalikar M, Vimalanathan M, Sahu A. Gonioscopy-assisted transluminal trabeculotomy (GATT) in Indian eyes – A description of 1-year follow-up results of the GATT procedure in a series of patients with open-angle glaucoma in South India. Indian J Ophthalmol Case Rep 2022;2:891-3

How to cite this URL:
Venkataraman G, Manju M, Chandran P, Dhavalikar M, Vimalanathan M, Sahu A. Gonioscopy-assisted transluminal trabeculotomy (GATT) in Indian eyes – A description of 1-year follow-up results of the GATT procedure in a series of patients with open-angle glaucoma in South India. Indian J Ophthalmol Case Rep [serial online] 2022 [cited 2022 Nov 27];2:891-3. Available from: https://www.ijoreports.in/text.asp?2022/2/4/891/358197

Glaucoma can be devastating for young patients because of its asymptomatic nature, and a significant proportion of them may present with monocular vision. Conventionally, partial-thickness procedures such as trabeculectomy have been the first procedure of choice for glaucoma in young patients. Any primary glaucoma surgery which spares the conjunctiva is a great boon to the patient as it offers more options for future interventions. The gonioscopy-assisted transluminal trabeculotomy (GATT) procedure was described by Feldman and Grover in 2014,[1] whereby an ab interno trabeculotomy is performed using a surgical goniolens and a micro-catheter. The same technique can also be performed using a 5-0 prolene suture (Aurolab, Madurai). The micro-catheter is an expensive device, and the easy availability of the prolene suture has made the adoption of the latter procedure very convenient and economical. This is a description of 1-year results of the GATT procedure in a series of patients with open-angle glaucoma from a tertiary care center in South India.

  Case Series Top

Written informed consent was obtained from every patient, and the study adhered to the tenets of the Declaration of Helsinki. Patients who only require glaucoma surgery were included, and patients requiring combined cataract and glaucoma surgery were excluded.

Surgical technique

All surgeries were performed by a single surgeon (GVR) under subtenon's anesthesia. After taking due asceptic precaution and using 1 mm keratome (1 mm straight blade, Aurolab Madurai), two side ports were placed at supero-nasal and infero-nasal quadrants. A 5-0 prolene suture was introduced into the anterior chamber (AC). Then the patient's head was tilted 35 degrees away from the surgeon, and the microscope was tilted 35 degrees toward the surgeon to view the nasal angle. The length of the suture is 10 cm with both ends cauterized and made mushroom-shaped. Using a surgical goniolens, the nasal trabecular meshwork (TM) was identified by the pigmentation. In eyes where there is no pigmented TM, blood in Schlemm's Canal (SC) was identified in the adjacent region to identify TM [Figure 1], as mentioned by Cubuk et al.[2]
Figure 1: (a) Identifying the trabecular meshwork. (b) Making a nick in the trabecular meshwork using a 26G needle. (c) Using grasping micro-forceps, the blunt tip of the suture is inserted into the Schlemm's canal. (d) The Schlemm's canal is canulated 360 degrees, and the leading edge of the tip is seen as it comes out of the opposite end of the Schlemm's canal

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A horizontal incision was made in the pigmented TM. The 5-0 prolene suture was introduced into the SC, and approximately 25 strokes were needed for complete cannulation. The leading edge is grasped using Grieshaber forceps, and with McPherson's forceps, the trailing edge of the suture is pulled, causing tension along the length of the suture that tears the inner wall of the SC resulting in the trabeculotomy, ab interno [Figure 2]. AC was washed off the visco-elastic material, and the eye was patched. Post-operatively, patients received steroid eye drops (1% prednisolone acetate) in tapering doses as well as antibiotic eye drops for 1 month.
Figure 2: (a) The leading edge of the suture is grasped with grasping forceps, and tension is created on the external suture length. (b) The Schlemm's canal is torn by pulling the external suture, whereas the leading tip is held in the anterior chamber. The suture free from the Schlemm's canal is removed from the eye. (c) The anterior chamber is washed off visco-elastic

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The mean age of the patients was 29.5 years (range 15–38 years). There were four male and four female patinets. The mean and median pre-operative IOP were 30.2 mmHg and 31 mmHg (range 18–44 mmHg), respectively. The mean and median post-operative IOP were 18.5 mmHg and 15.5 mmHg (range 12–40 mmHg), respectively. Six eyes had juvenile open-angle glaucoma (JOAG), pigmentary glaucoma (PDG), trabeculitis with open-angle glaucoma, anterior uveitis with open-angle glaucoma, and open-angle glaucoma with nevus of Ota, seen in one eye each. Two patients with JOAG underwent the procedure in both eyes [Table 1].
Table 1: Details of the patients

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All patients had self-limiting hyphema which resolved in 5–7 days. One patient had a 2 clock or iridodialysis. There were no other complications such as Descemet's membrane detachment and lens touch. All the patients were phakic. Two patients with secondary open-angle glaucoma (SOAG) had raised intra-ocular pressure (IOP) following the surgery.

  Discussion Top

The present case series describes the intermediate-term benefits of the GATT procedure in young glaucoma patients. Conventional trabeculectomy carries the risk of wipeout syndrome because of the prolonged hypotony during the procedure. In GATT, the risk of prolonged hypotony is minimal as all steps of the procedures require a well-pressurized globe.

The learning curve for the procedure was of relative ease because intra-operative gonioscopy is being practised for other procedures such as goniotomy, goniosynechiolysis, and anterior chamber foreign body removal. None of our patients had Descemet's membrane detachment or lens touch. One patient had 2 clock hours of iridodialysis. None of the patients had damage to the lens capsule; all of them were phakic, and this could be attributed to the deep anterior chamber available in these eyes.

Two patients with SOAG did not respond to the procedure.

  1. A patient with nevus of Ota – her IOP on the 15th post-operative day was 44 mm Hg. The patient finally underwent micro-pulse laser cyclophotocogaulation therapy after 11 months.
  2. A patient with viral uveitis failed at the end of the first-month follow-up, and she was managed conservatively. At the end of her second-month visit, she was also advised a glaucoma filtering procedure.

Eight eyes did not require glaucoma medication after the initial 2-month visit. All patients maintained their pre-operative visual acuity, and none of them developed cataracts during the follow-up period.

Aktas et al.[3] included 36 eyes of primary open-angle glaucoma (POAG) and 22 eyes of SOAG which had undergone only GATT. Their pre-GATT IOP was 24.36 mmHg and at 18 months showed an IOP reduction of 40.1%. The current study was of early exploratory nature, and we had a mean IOP of 30.2 mmHg at baseline and at the end of the last follow-up obtained an IOP reduction of 37.7%.

Our incidence of complications included hyphema, which was resolved within 5–10 days. One patient had a small iridodialysis. Our results are comparable to that of Baykara et al.,[4] wherein all patients did develop self-limiting hyphema, which was transient and did not prolong beyond the initial 10 days.

  Conclusion Top

To conclude, we could demonstrate the effectiveness of the GATT procedure to reduce IOP in the eyes of patients with open-angle glaucoma in South Indian patients. Ideal candidates are those with no systemic illness and not on any anti-coagulants or anti-hypertensive agents and with a normal open angle.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Grover DS, Godfrey DG, Smith O, Feuer WJ, De Oca IM, Fellman RL. Gonioscopy-assisted transluminal trabeculotomy, ab interno trabeculotomy: Technique report and preliminary results. Ophthalmology 2014;121:855-61.  Back to cited text no. 1
Cubuk MO, Unsal E. One-year results of gonioscopy-assisted transluminal trabeculotomy: Evaluation of prognostic factors. Eur J Ophthalmol 2021;31:460-8.  Back to cited text no. 2
Aktas Z, Ucgul AY, Bektas C, Sahin Karamert S. Surgical outcomes of prolene gonioscopy-assisted transluminal trabeculotomy in patients with moderate to advanced open-angle glaucoma. J Glaucoma 2019;28:884-8.  Back to cited text no. 3
Baykara M, Poroy C, Erseven C. Surgical outcomes of combined gonioscopy-assisted transluminal trabeculotomy and cataract surgery. Indian J Ophthalmol 2019;67:505-8.  Back to cited text no. 4
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