Ординатура / Офтальмология / Английские материалы / Step by Step Minimally Invasive Glaucoma Surgery_Garg, Melamed, Bovet, Pajic, Carassa, Dada_2006
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102 Step by Step Minimally Invasive Glaucoma Surgery
surgery as the primary approach.14 To date, 3 years followup data of a small pilot group that underwent combined erbium:YAG goniotomy and cataract surgery are available; and the IOP-lowering effect has not diminished over this follow-up period.15
EXCIMER-LASER-TRABECULOTOMY (ELT)
Background
In the meantime, the CE-certified AIDA excimer laser (TuiLaser AG, Germering, Germany) has become commercially available (Fig. 7.1). We therefore switched from the erbium:YAG system prototype to the certified laser, assuming that it should have a comparable effect. Like the erbium:YAG laser, the AIDA excimer laser reestablishes the outflow of aqueous humor through conventional drainage pathways. By excising a defined
Fig. 7.1: The AIDA excimer laser (TuiLaser AG, Germering, Germany)
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area of trabecular meshwork, juxtacanalicular tissue, and the inner wall of Schlemm’s canal via a fiberoptic probe delivering 308 nm XeCL excimer laser energy, aqueous outflow is re-established.16 The creation of the openings through the trabecular meshwork and the inner wall of Schlemm’s canal is accomplished by using the fiberoptic delivery system LAGO 200 or LAGO 200 ENDO. In detail, the fiberoptic system is positioned across the anterior chamber to contact the trabecular meshwork. Laser pulses remove tissue to create a fistula into Schlemm’s canal. Direct viewing for positioning of the fiber is performed with either a goniolens or an endoscope. The small size of the delivery system (external diameter 0.5 mm for the LAGO 200, 1.3 × 0.95 mm for the LAGO 200 ENDO, coaxial endoscope) ensures access through a self sealing clear cornea incision (Figs 7.2 and 7.3). Twenty laser pulses are adequate to create a permanent opening into Schlemm’s canal. Once the corneal incision is prepared, the actual
Fig. 7.2: Photomontage of the fiberoptic system contacting the opposite trabecular meshwork
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Fig. 7.3: Operative setting: The ELT probe has been inserted via a clear cornea incision and approaches the opposite trabecular meshwork
procedure requires about three minutes. The procedure can easily be combined with cataract surgery. The wavelength of the AIDA laser - 308 nm has been found to ablate the trabecular meshwork without inducing thermal damage, thereby minimizing fibrous tissue healing reactions17-19 (Fig. 7.4).
Surgical Procedure
ELT can easily be performed through a clear cornea tunnel incision as used for cataract surgery. We constrict the pupil with topical pilocarpine 2 percent or intracameral injection of acetyline chloride (i.e. Miochol®), then inject a viscoelastic gel (i.e. Healon) into the anterior chamber and insert the laser probe. We then advance the probe to the
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Fig. 7.4: Histology demonstrated that the wavelength of the AIDA laser ablates the trabecular meshwork without inducing thermal damage, thereby minimizing fibrous tissue healing reactions
opposing chamber angle under gonioscopic or endoscopic visualization. The application of the laser pulses can be controlled when the probe tip is in contact with the trabecular meshwork (Figs 7.5 and 7.6). The probe tip is then repositioned such that ten trabecular meshwork perforations are created to the inferior 180°. Following removal of the probe (and endoscope), the viscoelastic is exchanged by BSS. Postoperatively, all eyes are treated with topical steroids 4x/d tapered over 3 weeks. In case of a persistent fibrin reaction, atropine 1 percent eye drops 2x/d can be added. In case of combined cataract + ELT procedure, we first perform cataract surgery followed by the ELT procedure, which takes about three minutes longer than cataract surgery alone.
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Fig. 7.5: ELT: Endoscopic view showing the fiberoptic delivery approaching the trabecular meshwork
Fig. 7.6: ELT: Two trabeculotomies are already created. Note: The retrograde bleeding from Schlemm’s canal which we take as a sign of successful perforation
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Study Results
Pooled data from a number of study groups have demonstrated that ELT is a safe and sufficient IOP-lowering procedure that can easily be combined with cataract surgery.20
In our own clinic, we have retrospectively studied a group of 135 patients with open-angle glaucoma (n = 128) and ocular hypertension (n = 7) that were divided into two groups: (a) ELT as a stand-alone procedure (n=75), (b) combined cataract and ELT procedure (n= 60). Both groups were further divided into 2 subgroups: (1) Preoperative IOP > 22 mmHg, (2) Preoperative IOP • 22 mmHg. KaplanMeier survival curves were calculated. Success criterion was 20 percent decrease of IOP in combinaton with IOP
•21 mmHg and postoperative IOP-lowering medication
•preoperative IOP-lowering medication. Follow-up time was 1 year. For group a) ELT, 1. Preoperative IOP > 22 mmHg, 2. Preoperative IOP • 22 mmHg: Kaplan-Meier survival curves showed a success rate of 57 percent in subgroup 1 and of 41 percent in subgroup 2 (Figs 7.7 and 7.8) For group b) Combined cataract and ELT procedure, 1. Preoperative IOP > 22 mmHg, 2. Preoperative IOP • 22 mmHg: Success rate was 91 percent in subgroup 1 and 52 percent in subgroup 2 (Figs 7.9 and 7.10).
Side effects of the ELT were rare: In two cases, an iris adhesion at the tunnel occurred, in 3 cases there was a fibroid reaction that responded very well to topical steroids. One patient developed an occlusion of the central retinal vein 5 months after surgery. IOP however was wellcontrolled at that time, indicating that there was no connection between the CRVO and the ELT procedure.
Our data indicate that ELT is not only a safe and efficient IOP-lowering procedure, but also that it is most effective
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Fig. 7.7: ELT: Kaplan-Meier-survival curve, preoperative IOP > 22 mmHg
Fig. 7.8: ELT: Kaplan-Meier-survival curve, preoperative IOP • 22 mmHg
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Fig. 7.9: ELT+Phako: Kaplan-Meier-survival curve, preoperative > 22 mmHg
Fig. 7.10: ELT+Phako: Kaplan-Meier-survival curve, preoperative • 22 mmHg
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in patients with a high preoperative IOP. The 2-year-follow- up data are now available for many patients, and it seems obvious that the IOP-lowering effect of ELT is conserved also after this longer period of time. We have a prospective multicenter study ongoing in this field and are looking forward to its result.
Due to its sufficient IOP-lowering effect and the minimal invasiveness of the procedure, ELT has become the therapy of choice for patients who suffer from cataract and glaucoma. We recommend the combined procedure in all cataract patients with an IOP of more than 22 mmHg without therapy. ELT as a stand-alone procedure is performed in patients whose IOP is above 22 mmHg despite maximally tolerated therapy. In patients with low preoperative IOP, such as patients with normal-tension glaucoma, ELT has proven to be less powerful. We assume that in such cases, the episcleral venous pressure limits the chances of success and prefer a trabeculectomy instead.
CONCLUSION
Excimer-Laser-Trabeculotomy is a promising IOPlowering technique both as a stand-alone procedure and in combination with cataract surgery. It is especially suitable for patients with high preoperative IOP levels and can easily be combined with cataract surgery.
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