GONIOSCOPY ASSISTED TRANSLUMINAL TRABECULOTOMY

GUEST AUTHOR

NAWAZISHA

AJMAL KHAN TIBBIYA COLLEGE,

ALIGARH, INDIA

INTRODUCTION

Currently the technique most commonly employed for glaucoma filtration surgery (GFS) is ab externo trabeculectomy of Cairns.

However, this technique is fraught with a large number of complications.

One of the main reasons trabeculectomy tends to fail over time is due to development of sub-conjunctival fibrosis. Known as the “Ring of Steel” and the “Band of Steel”, these changes progressively reduce aqueous outflow through the sclerostomy. In order to reduce the occurrence of fibrosis anti-metabolites such as Mitomycin-C and 5-Flurouracil have been used. Unfortunately, these chemicals have the potential to cause sight-threatening complications, such as endophthalmitis.

Recently a new technique which employs a minimally invasive 360⁰ ab interno trabeculotomy has been described. This is known as “GONIOSCOPY ASSISTED TRANS-LUMINAL TRABECULOTOMY (GATT)”.

PROCEDURE

This article describes the main features of this surgical procedure.

STEP 1: Standard sterile preparation and eye draping with insertion of an open wire nasal lid speculum is done.

STEP 2: A 23-gauge needle paracentesis track oriented tangentially is placed in the supero-nasal or infero-nasal quadrant.

STEP 3: A viscoelastic (Sodium hyaluronate) is injected into the anterior chamber through this site.

STEP 4: A temporal paracentesis is created and a suture (5-0 prolene) or microcatheter into the anterior chamber through this entry site such that the tip rests in the nasal angle.

STEP 5: Position the microscope and patient’s head in order to allow proper visualization of the nasal angle with a Swan-Jacob goniolens.

STEP 6: A 1-2 mm goniotomy is created in the nasal angle with a microsurgical blade through the temporal site.

STEP 7: Microsurgical forceps are introduced through the temporal paracentesis and used to grasp the microcatheter or suture iwithin the anterior chamber.

STEP 8: The distal tip of the microcatheter/suture is inserted into the Schlemm’s Canal.

STEP 9: Within the anterior chamber the microsurgical forceps are used to advance the catheter through the Schlemm’s Canal circumferentially 360⁰. The progress of the microcatheter is noted by observing the illuminated tip.

STEP 10: After retrieving the distal tip once the catheter has passed 360⁰ around the canal, the catheter tip is externalized from the temporal corneal incision creating the first half of the 360⁰ trabeculectomy.

STEP 11: Then traction is placed on the proximal aspect of the catheter creating a 360⁰ ab interno trabeculectomy.

STEP 12: The viscoelastic is removed from the anterior chamber by a 2-handed irrigation-aspiration system to wash the anterior chamber of blood.

STEP 13: Near the end of the procedure the AC was kept filled 25% with viscoelastic to tamponade for any bleeding.

STEP 14: The wound is checked for water-tightness.

POST-OPERATIVE CARE

Subconjunctival or intracameral steroids and antibiotic injections are given (according to surgeon’s discretion).

Follow-up: The topical antibiotics-steroids are stopped at post-operative 1 week.

The IOP is monitored during this period to look for steroid-induced response.

The follow-up took place at: Day 1 - 1 week - 2 to 3 weeks - 1 month - 3 months- 6 months- thereafter every 3 to 6 months.

At each follow-up visit the following data were collected:

• Visual acuity.
• Intra-ocular pressure.
• Number of glaucoma medications.
• Surgery related complications.
• Gonioscopic findings.

COMPLICATIONS

The most common complication was hyphema, seen in 30% patients at 1-week visit.

Others include:

• Choroidal folds.
• Steroid-induced IOP spikes.
• Shallow AC.

RESULTS

At 6 months follow-up, 85 patients who underwent GATT were evaluated. IOP decreased by 7.7 mmHg (Standard deviation [SD]: 6.2 mmHg; 30%), average decrease in glaucoma medications of 0.9. in the secondary glaucoma group IOP decreased by 17.2 mmHg with average of 2.2 fewer glaucoma medications. Treatment was considered failed in 9% because of the need for further glaucoma surgery. Lens status or concurrent cataract surgery did not have a statistically significant effect on IOP in eyes which underwent GATT.

ADVANTAGES

1.      

1.  Much safer and less invasive than ab externo trabeculectomy; it requires making only 2 small paracentesis.
2.  It restores flow through the eye’s natural drainage system.
3.  It takes much less time to perform than ab externo trabeculectomy.
4.  It doesn’t violate the conjunctiva; so it doesn’t limit future surgical options.
5.  It is cost-effective.
6.  It is very safe, with few complications.
7.  It is very effective in lowering IOP.