Ординатура / Офтальмология / Английские материалы / Step by Step Minimally Invasive Glaucoma Surgery_Garg, Melamed, Bovet, Pajic, Carassa, Dada_2006

24 Step by Step Minimally Invasive Glaucoma Surgery

INTRODUCTION

Lasers have been in use for the treatment of glaucoma for the last few decades. A bloodless sutureless technique of using the Nd:Yag laser has been started by the authors (SA) to treat glaucoma. This is called laser sclerotomy. If the patient has a cataract then one can do the cataract removal with the Laser Phakonit technique followed by either a Rollable or Foldable IOL implantation.

HISTORY

The author first performed this technique on a diabetic patient who was already undergoing hemodialysis as a result of renal failure. His renal failure made the use of acetazolamide an absolute contraindication. Using the ND:Yag laser of the Paradigm machine which is also used for cataract surgeries by the author, the author performed the laser sclerotomy. In this, the idea was to create a hole via the clear corneal incision in the trabecular meshwork. The hole passes through and through to exit the sclera forming a filtering channel into the subconjunctival space.

ND:YAG LASER

It is a solid state laser having an ionizing effect causing photodisruption, thermal effect causing photovaporization, photocoagulation and photocarbonization. The laser fiberoptic (Fig. 3.1) has a Helium Neon aiming beam with the diameter of the optic end being 380 μ. This fiberoptic is encased within a silicon sleeve. The ‘male socket’ connects the fiberoptic to the laser machine. The laser machine the author advocates is the Paradigm Photon machine which works at 3 Watts.

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Fig. 3.1: Nd:YAG laser fiberoptic (1) laser fiberoptic (2) male socket

(3) diameter of ocular end of laser fiberoptic is 380 (4) helium neon aiming beam

LASER SCLEROTOMY WITH ND:YAG –

INSTRUMENTATION

•0.9 mm diamond blade: Custom made diamond blade similar to the one used in laser Phakonit.

•Viscoelastic: Hydroxy methyl cellulose used for maintenance of anterior chamber with protection of corneal endothelium.

•Nd:Yag laser fiberoptic.

•Paradigm laser machine.

SURGICAL TECHNIQUE

Paracentesis

The anterior chamber is filled initially with viscoelastics to facilitate a smooth incision (Fig. 3.2). Hydroxymethyl propyl cellulose (viscon) is the preferred viscoelastic. The site of paracentesis is preferably 45 degrees away from the main incision so that a repository may be used later on for control of the eye ball during the procedure.

26 Step by Step Minimally Invasive Glaucoma Surgery

Fig. 3.2: Paracentesis with viscoelastic injection

Clear Corneal Incision

A keratome/diamond blade of 0.9 mm size (Fig. 3.3) is used to make a clear corneal incision superiorly depending on the site planned for sclerotomy. The entry point may be directly opposite the planned site of sclerotomy or juxtaposed to the planned site of sclerotomy. Depending on the surgeon’s preferences the director of the blade may be adjusted accordingly with the initial entry point parallel to the limbus and the tunnel incision varying according to the planned site of sclerotomy. Recently the author has opted for a variation in the conventional corneal tunnel with the initial entry point parallel but about 2 mm away from the limbus and the tunnel directed towards the limbus. The sclerotomy is then performed in the same area.

Laser Sclerotomy

After the corneal incision is made the anterior chamber is filled with more viscoelastic (Fig. 3.4) and then the laser

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Fig. 3.3: 0.9 mm diamond blade for clear corneal incision

Fig. 3.4: Anterior chamber filled with viscoelastic

fiberoptic (Fig. 3.5) is introduced through the clear corneal incision. A short burst of laser is given directly opposite the intended site of sclerotomy (Fig. 3.6). The procedure is

Laser Sclerotomy 29

performed without the need of an operative goniolens using just the aiming beam as a guide. When the aiming beam is seen about 1.5 mm (Fig. 3.7) from the limbus a short burst of laser brings the laser fiberoptic out of the scleral bed and under the conjunctiva. Following this the fiberoptic is removed and the anterior chamber washed with BSS to remove traces of viscoelastic. BSS is injected near the sclerotomy site and sub-conjunctival bleb formation (Fig. 3.8) is looked for to assess the patency of the sclerotomy.

Peripheral Iridectomy

Depending on whether a PBI was done before or not a peripheral iridotomy (Fig. 3.9) may be done near the area of sclerotomy using the laser itself but preferably only in pseudophakic or aphakic patients lest the crystalline lens gets damaged inadvertently.

Fig. 3.7: Laser ablation carried through the sclera 1.5 mm from corneal limbus

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Closure of Incision

The clear corneal incision is closed by stromal hydration (Fig. 3.10).

Laser Phakonit and IOL Implantation

If the patient has a cataract then one can perform the cataract extraction with the Laser Phakonit technique followed by an IOL implantation. This concludes a triple procedure which is less traumatic than performing a triple procedure with trabeculectomy.

Phakic Laser Sclerotomy

Laser sclerotomy has been performed safely in phakic individuals. Care has to be exercised when the laser is used, to prevent inadvertent damage of the crystalline lens with

Fig. 3.10: Anterior chamber is reformed and incision sealed with stromal hydration