NON-PENETRATING GLAUCOMA SURGERY

Dr.Jyoti ShettyMedical Director,

Bangalore West Lions Superspeciality Eye Hospital

PRINCIPLE

Intended to facilitate the passage of aqueous humor through the trabeculum and Schlemm's canal bypassing the the juxta-canalicular meshwork which is the site of highest resistance to aqueous outflow without opening the anterior chamber and decompressing the eye.

SCHLEMS CANAL

ROOF OF SCHLEMS CANAL

TRAB MESHWORK

ANTERIOR CHAMBER

INDICATIONS

Patients requiring target IOP at moderate levels between 15-18mmHg with poor compliance for medical therapy to achieve the same.

TECHNIQUES

Ab-externo trabeculectomy- Eduardo Arenas

Viscocanalostomy- Robert StegmannDeep sclerectomy -Mermoud Laser trabecular ablation - Arturo

Maldonado-Bas

Ab-externo trabeculectomy

Involves removal of the diseased endothelial layer of Schlemm’s canal and the Juxtacanalicular Trabecular Meshwork using a diamond microdrill.

Ab-externo trabeculectomy-

Conjunctival Flap A deep scleral flap is

dissected (2.5x1.5mm) such that the roof of the Schlemms Canal is reached and then it is unroofed.

2.5mm

1.5mm

In the floor of the scleral flap, aqueous leak will be seen if the Schlemm’s Canal has been unroofed .

Mitomycin-C(0.08%) is then applied under the scleral flap.

Scleral flap

Unroofed Schlems canal

The diamond microdrill is then used to remove the floor of the Schlemm’s Canal and the juxta-canalicular meshwork

Tight conjunctival closure..

Diamond Microdrill

According to Arenas, an opening of 100µ is sufficient for functional drainage as Aqueous Humour elimination from AC is a very passive and metabolic process-A big fistula is not required to control IOP.

DEEP SCLERECTOMY

Fornix or limbal based conjunctival flap.

Superficial scleral flap - 5 x 5 mm ,1/3 of the scleral thickness (300 microns).

In order to be able to dissect down to Descemet’s membrane later, the scleral flap is dissected 1 to 1.5 mm into clear cornea

5mm

5mmDissection extended 1-1.5mm into clear cornea

A deep scleral flap is then dissected to 95% of remaining thickness of the sclera

.

Superficial Scleral Flap

Deep Scleral Flap

Schlemm’s canal is unroofed at the level of the scleral spur to expose the TM

Descemet’s membrane is carefully dissected away from the corneal stroma using a sponge or a spatula

When the anterior dissection is complete, the deep scleral flap is cut anteriorly

Endothelium of floor of Schlemm’s canal and the juxtacanalicular portion of the trabeculum are peeled off

When the anterior dissection is complete, the deep scleral flap is cut anteriorly

Endothelium of floor of Schlemm’s canal and the juxtacanalicular portion of the trabeculum are peeled off

To avoid a secondary collapse of the superficial flap over the Trabeculo-Descemet’s membrane and the remaining very thin scleral bed, an implant is placed in the scleral bed.

Implants- Porcine collagen, Reticulated hyaluronic acid HEMA

Implant sutured onto the scleral bed

Two interrupted 10-0 nylon sutures are used to suture the the scleral flap.

The conjunctiva is closed with wet field cautery.

VISCOCANALOSTOMY

Fornix or limbal based conjunctival flap.

Superficial scleral flap - 5 x 5 mm ,1/3 of the scleral thickness (300 microns).

In order to be able to dissect down to Descemet’s membrane later, the scleral flap is dissected 1 to 1.5 mm into clear cornea

A deep scleral flap is then dissected to 95% of remaining thickness of the sclera

Schlemm’s canal is unroofed at the level of the scleral spur to expose the TM. Superficial

Scleral Flap

Deep Scleral Flap

A finely polished cannula with an outer diameter of 150 µm is introduced into and a Schlemm's canal, and a high-viscosity viscoelastic (Healon GV) is injected 4.0 to 6.0 mm on each side.

Dilated cut ends of Schlemm’s Canal after Visco injection

The viscoelastic injection increases the diameter of Schlemm's canal from its usual diameter of 25 to 30 µm to about 230 µm and increases the patency of the outflow channels

Aqueous is removed by a paracentesis to prevent rupture of TDM.

Descemet's membrane is separated 1 to 2 mm from the corneoscleral junction by applying gentle pressure on Schwalbe's line using a cellulose sponge.

This creates an intact window in Descemet's membrane through which aqueous humor diffuses from the anterior chamber into the subscleral lake bypassing the inner wall (floor) of Schlemm's canal.

The deep scleral flap is then excised at its base The superficial flap is sutured using five 11-0 nylon

suture in a watertight manner Viscoelastic is subsequently injected into the subscleral

lake. The conjunctival flap is closed with sutures.

LASER TRABECULAR ABLATION

Topical anesthesia fornix based

conjunctival flap A circle straddling the

limbus marked with the help of a 4.25 mm optic zone marker

A corneo scleral incision with a diamond knife calibrated at 350 microns.

The flap is dissected and bent forward over the clear cornea to expose the area that will be treated

Reflected scleral flap

A specially designed mask with a 2 x 4 mm window, is placed to protect the surrounding tissue from the excimer rays

Mask with 2x4mm window

The ablation of the deep scleral wall is made using PTK software that removes successive layers of 0.25 to 2 microns

Ablation proceeds in the following order- Deep sclero- corneal tissue Roof of Schlemms canal Part of its internal wall Adjacent corneal stroma 1 millimeter in front of the

Schlemm’s canal Ablation is continued up to the moment when a

drop of aqueous humor appears

CANALOPLASTY

360 degree viscodilatation of Schlemm’s canal with an illuminated beacon tipped microcatheter.

Diameter of the microcatheter -200µA 10-0 prolene suture is also passed

through the entire Schlemm’s canal and tightened towards the AC-Produces a further 2-3mm fall in IOP.

COMPLICATIONS

1)Moderate transient hypotony in the first post-operative week.

2)High IOP on 1st post op day-Due to insufficient dissection of the TDM.Treated with Nd:YAG goniopuncture.

3)Rupture of the TDM postoperatively-Due to vigorous eye rubbing,valsalva.Due to rupture of the TDM,iris prolapse occurs and blocks the filtration site causing elevation of IOP . Treatment-revision of the filtration site and conversion into a conventional trabeculectomy

4)PAS at filtration site-Treated with YAG iridoplasty

5)Descemets Membrane detachment-Rare complication. More common with Viscocanalostomy.Usually transient.Severe cases, Descemets Membrane reposition maybe necessary.

6)Scleral ectasia-Rare complication

RESULTS

Deep Sclerectomy provides much better results when performed using implants or antimetabolites or both.

Viscocanalostomy shows the same results with or without implants and antimetabolites

When the above were compared with trabeculectomy,72% of patients who underwent trab. With antimetabolite achieved a target IOP of <21mmHg .51% of patients who had deep Sclerectomy with implant and 34% of patients who underwent Viscocanalosiomy with antimetabolite achieved a target IOP <21mmHg .