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

292 Step by Step Minimally Invasive Glaucoma Surgery

Table 17.1: Comparison of laser candidates for glaucoma treatment

the fixed fiber core. In contrast, the optic-based system gives a fairly steady output even during prolonged usage (Fig. 17.6).

In Argon laser trabeculoplasty (LTP), focal burns with an argon laser beam of 50 micron spot size and 1000 mW power for 0.1 seconds causes contraction of the meshwork tissues. This causes separation of the adjacent trabecular sheets to increase the outflow of aqueous. Additionally the laser burns induce alteration in phagocytic activity of the trabecular cells.20 LTP does succeed in lowering the IOP in 70–75 percent of patients with open-angle glaucoma.21 Over time the effectiveness decreases so that 5 years after treatment only 30 to 60 percent of patients maintain good intraocular pressure control.22 Basically, the type of filtration channel created by tissue ablation of UV or IR

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Fig. 17.6: Picture of linear radial laser sclerostomy

laser differs little from that created by surgical Trabeculectomy or NPDS. Preliminary studies indicate good initial IOP reduction. The main advantage of CLAFS is that the ablation pattern can be tailor-made to suit the target pressure. There appears to be adequate justification to expect that the long-term results of this minimallyinvasive procedure is likely to be the same or better than that of the more invasive, conventional filtration procedures.

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REFERENCES

1.Krasnov M. Microsurgery of glaucoma: indications and choice of technique. Am J Ophthalmol 1969;67:857-64.

2.Krasnov MM. Current technic of sinusotomy (externalization of Schlemm’s canal) without resection of the sclera. Vestn Oftalmol 1988;104:102-04.

3.Zimmerman TJ, Kooner KS, Ford VJ, et al. Trabeculectomy vs nonpenetrating trabeculectomy: a retrospective study of two procedures in phakic patients with glaucoma. Ophthalmic Surg 1984;15:734-40.

4.Zimmerman TJ, Kooner KS, Ford VJ, et al. Effectiveness of nonpenetrating trabeculectomy in aphakic patients with glaucoma. Ophthalmic Surg 1984;15:44-50.

5.Delarive T, Mermoud A, Uffer S, Rossier A. Histological findings of deep sclerectomy with collagen implant in animal model. Proceedings of the First International Congress on Non-penetrating Glaucoma Surgery. Lausanne, February 2001.

6.Sourdille P, Saniago PY, Ducourneau Y. Non-perforating surgery of the trabeculum with reticulated hyaluronicacid implant. J Fr Ophthalmol 1999; 22:794-97

7.Schuman JS, Stinson WG, Hutchinson BT, et al. Holmium laser sclerectomy. Success and complications. Ophthalmology 1993;100:1060-65.

8.March WF, Gherezghiher T, Koss MC, Nordquist RE. Experimental Y AG laser sclerostomy. Arch Ophthalmol 1984;102:1834-36.

9.March WF, Gherezghiher T, Koss MC, et al. Histologic study of a neodymium-YAG laser sclerostomy. Arch Ophthalmol 1985;103:860-63.

10.Wetzel W, Haring G, Brinkmann R, Birngruber R. Laser sclerostomy ab externo using the Erbium:Y AG laser: first results of a clinical study. Ger J Ophthalmol 1994;3:112-25.

11.Wetzel W, Otto R, Falkenstein W, et al. Development of a new Er:YAG laser conception for laser sclerostomy ab

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externo: experimental and first clinical results. Ger J Ophthalmol 1995;4:283-88.

12.Wetzel W, Schmidt ED, Haring G, et al. Laser sclerostomy ab externo using two different infrared lasers: a clinical comparison. Ger J Ophthalmol 1995;4:1-6.

13.Brooks AM, Samuel M, Carroll N, et al. Excimer laser filtration surgery. Am J OphthalmoI1995;119:40-47.

14.Campos M, Lee PP, Trokel SL, et al. Transconjunctival sinusotomy using the 193-nm excimer laser. Acta Ophthalmol Copenh 1994;72:707-11.

15.Traverso CE, Murialdo D, Di LG, et al. Photoablative filtration surgery with the excimer laser for primary openangle glaucoma: a pilot study. Int Ophthalmol 1992;16:36365.

16.Stegmann RC. Viscocanalostomy: a new surgical technique for open-angle glaucoma. An Inst Barraquer Spain 1995;25:229-32.

17.Stegmann R, Pienaar A, Miller D. Viscocanalostomy for open-angle glaucoma in black African patients. J Cataract Refract Surg 1999;25:316-22.

18.Klink T, Lieb W, Grehn F. Erbium: YAG laser-assisted deep sclerectomy. Invest Ophthalmol Vis Sci 1999;40:272.

19.Klink T, Lieb W, Grehn F. Erbium: YAG laser-assisted preparation of deep sclerectomy. Grafes Arch Clin Exp Ophthalmol 2000;238:792-96.

20.Ticho U, Cadet JC, Mahler J, Sekelese, amd Bruchin A. Argon laser trabeculotimies in Primates: evaluation by histological and perfusion studies. Invest Ophthalmol Vis Sci 1978;17:667.

21.Grinich NP, van Buskirk EM, Samples JR. Three-year efficacy of argon laser trabeculoplasty. Ophthalmology 1987;94:858.

22.Shingleton BF, Richter CU, Bellows AR, Hutchinson BT, Glynn RJ. Long-term efficacy of argon laser trabeculoplasty. Ophthalmology 1987;94:1513.

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INTRODUCTION

Increased intraocular pressure (IOP) accompanied by evidence of damage to the optic nerve requires a life-long treatment to maintain the pressure at acceptable levels. The new generations and combinations of medical therapy are indeed highly effective, however, they all require continuous instillation, at least once a day and often more, of eyedrops. Local side effects are significant and compliance is, therefore, a major problem in glaucoma medical therapy. Studies have shown that glaucoma surgery, namely trabeculectomy, is at least as effective as medications, and obviously does not require patients’ compliance. However, surgery may be associated with numerous complications such as hypotony, shallow anterior chamber, endophthalmitis, leaking blebs and many others. Successful procedures are associated with a 3-fold increase in cataract formation, as may occur in any penetrating ocular procedure.

Non-penetrating filtration surgery (NPFS) is, therefore, a very appealing option. Since the anterior chamber is not penetrated, the procedure is actually an extraocular operation. A success rate similar to conventional trabeculectomy without the complications of intraocular surgery seems to offer as an ideal solution. However, dissection of the scleral wall to over 95 percent of its depth until fluids effectively percolates, without penetration into the eye, require very high skills and a long learning curve. Only a few highly experienced surgeons adopted this technique, which in spite of its obvious advantages did not gain a wide popularity. Also, several studies reported clinical results somewhat below the pressure reduction achieved by conventional trabeculectomy. Many modifications, such as placing spacers under the scleral flap, YAG laser goniopuncture and antimetabolites applications

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improved the efficacy of the procedure however not yet to the level of a wide acceptance. Attempts to apply laser technology to NPFS were previously reported, including excimer, holmium, and erbium:YAG lasers, however none was practically accepted.

In the last years we looked for surgical techniques that would make NPFS both a simple procedure, suitable for any anterior segment surgeon, as well as clinically effective. Utilizing some of the unique features of the CO2 laser seemed theoretically optimal for this goal.

The CO2 laser is very effective in ablating dry tissues, and is therefore widely used in general and plastic surgery. However, the far-infrared radiation of this laser is absorbed in water within a very short penetration depth and is thus ineffective when applied over wet tissues. We speculated that application of laser energy on the dried scleral tissue, over the trabecular meshwork, would cause a localized ablation of the sclera until fluid starts percolating through the thinned wall. When the aqueous wets the ablated area further laser applications would be ineffective, and would not cause any further tissue ablation (i.e. perforation). Thus, tissue ablation would cease “automatically” when the desired end-point of the procedure is achieved, i.e. aqueous percolation without perforation into the anterior chamber. The surgical procedure is quite simple and does not require any specific skills other than creation of a scleral flap. Use of a scanning device may further assist surgery by predetermining and accurately controlling the shape of the ablated tissue block and the energy distribution (Figs 18.1A to D).

The CO2 laser that we used in our initial studies was the Kaplan PenduLaser 115® CO2 laser system (Optomedic Medical Technologies Ltd., Or Yehuda, Israel). This is the smallest and the most portable and compact CO2 laser in