Ординатура / Офтальмология / Английские материалы / Glaucoma Surgery_Trope_2005
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Increasing the surface area of treatment results in a much more diffuse noncystic area clinically. A large area prevents the development of a ring of scar tissue (the “ring of Steel”), which restricts flow and promotes the development of a raised cystic avascular bleb.
4.1.5.Antimetabolite Treatment Duration and Washout
Dr. Khaw treats for 3 min. If he needs to vary the effect of MMC, he varies the concentration. He uses only two concentrations (0.2 and 0.5 mg/mL). For intraoperative 5FU he always uses 50 mg/mL. He washes out with 20 mL of balanced salt solution.
Explanation. Pharmacokinetic experiments we have done show a rapid uptake over 3 min after which there is a plateau when relatively little drug is added for extra minutes. In the period from 1 to 3 min there is considerable variation in the dose delivered (16).
4.1.6. Scleral Flap Sutures New Adjustable, Releasable, and Fixed
The sclerostomy is created and secured with a mixture of fixed and releasable sutures. Dr. Khaw has developed a new type of adjustable suture which he has evolved for about 2 years. These allow the tension to be adjusted postoperatively through the conjunctiva. Specially designed forceps with very smooth edges are used for this adjustment of pressure (Duckworth and Kent 2-502) (Fig. 4.5).
Explanation. If strong antimetabolites such as MMC are used, complete suture removal can lead to a sudden drop in intraocular pressure even many months after surgery. An adjustable suture system allows a gradual titration of the intraocular pressure more gradual than that seen with suture removal or massage (17).
4.1.7.Conjunctival Closure
The main reason fornix-based flaps are not popular despite the increased speed, much better exposure, and absence of a scar in the line of aqueous flow leading to more cystic blebs is the inconvenience of aqueous leakage at the limbus in the postoperative period. To get rid of this problem and take advantage of a fornix-based bleb
Figure 4.5 (See color insert) New adjustable sutures being adjusted through the conjunctiva using special finely machined forceps. For video, see http://www.ucl.ac.uk/ioo/research/khaw.htm
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Dr. Khaw has used several strategies |
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. No side cut in the conjunctiva |
this minimizes manipulation and side leakage. |
. Ensure Tenons is engaged in every stitch rather than just conjunctiva.
. Minimize any contact with antimetabolites, for example, with clamp.
. Side purse string sutures and deep attachment sutures buried in corneal grooves; 10/0 nylon is used throughout.
4.2.Postoperative Application of Antimetabolites
Postoperative injections of 5FU can be used postoperatively on their own, or even after intraoperative MMC or 5FU have been used. Subconjunctival injections of MMC have been given, but occasionally significant complications have been reported, so we do not use MMC injections routinely. 5FU was originally used as a planned regimen following surgery, but with the advent of intraoperative metabolites, the 5FU injections are now usually used according to the clinical situation at each post operative visit.
4.2.1.Indications
1.As part of a planned regimen in a patient with a significant risk of scarring or requiring a low postoperative intraocular pressure.
2.In a patient showing signs of scarring and imminent bleb failure.
3.Following a needling or re-exploration procedure.
4.To prevent failure of an existing bleb after a healing stimulus (e.g., cataract extraction surgery).
5.Injections may be given up to several months after surgery, if there is a persistent healing response and the intraocular pressure is rising.
4.2.2.Technique for Postoperative 5FU Injection
The technique of postoperative injection is important. Laboratory experiments show that the degree of effect of antimetabolites on fibroblasts depends on either concentration or duration of exposure, hence the logic for using a very high concentration of 5FU intraoperatively in the surgical area (7,8).
1.The eye is anaesthetized with several drops of topical amethocaine. It may also be useful to blanch the conjunctiva with a drop of adrenaline 0.01% or pheneylephrine 2.5% if there is no contraindication, as this may reduce the incidence of postinjection subconjunctival hemorrhage.
2.Quantity and concentration. The original regime involved injections of 5 mg of 5FU diluted with 0.5 mL of saline. 5FU is now generally given in a concen-
tration directly from the bottle, which is either 0.1 mL of a 50 mg/mL solution or 0.2 mL of a 25 mg/mL solution (i.e., injection dose 5 mg).
3.A thin needle is advantageous as it reduces the reflux of 5FU into the tear film. For convenience we use a presterilized insulin syringe with an integral 27-gauge needle.
4.A lid speculum is inserted to improve access.
5.Site of injection. 5FU was originally given 1808 from the bleb to minimize the risk of intraocular entry of the 5FU solution which has an alkaline pH of 9. Dr. Khaw now gives the injection about 908 from the bleb to maximize the effect. Occasionally, the injection can be given deep in the upper fornix away from the drainage bleb if there is very good exposure. The conjunctiva is
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Figure 4.6 (See color insert) Injection of 5FU being given through a viscoelastic wall.
gently lifted with a nontoothed forceps and the needle inserted subconjunctivally. If the needle is too deep, there is a danger of scleral bleeding and direct tracking into the eye. The bleb resulting from the injection is slowly raised and watched as it advances towards the drainage bleb area, and injecting should stop just before the injection bleb meets the drainage area. Great care should be taken, particularly in a soft eye, as 5FU may enter the eye much more easily in a soft eye.
6.The needle should be left in place for a few seconds as this helps to seal off the entry site and reduce leakage of 5FU into the tear film.
Figure 4.7 (See color insert) Example of diffuse noncystic bleb with intraocular pressure of 12 mmHg 5 years after surgery using mitomycin 0.5 mg/mL and described techniques. This result may be possible for the majority of patients having filtration surgery with improvements of current techniques, and can lead to a dramatic reduction in complications.
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7.Any remnant 5FU in the tear film should be irrigated out. If amethocaine eyedrops are used after a 5FU injection, a fine white precipitate in the tear film indicates that there is 5FU present. Washing out the fornix may reduce the incidence of corneal complications.
8.Dr. Khaw has developed a new technique of 5FU preceded by subconjunctival Haelon GVTM. This “viscoelastic wall” prevents leakage of 5FU back into the
tear film and enhances the effect of the 5FU (Fig. 4.6).
5.SUMMARY
Simple changes in the method of intraoperative antimetabolite application coupled with changes in surgical technique can very greatly increase the long-term safety of filtration surgery (Fig. 4.7).
ACKNOWLEDGMENTS
Dr. Khaw research has been supported in part by the Medical Research Council (G9330070), the Guide Dogs for the Blind, the Wellcome Trust, Fight for Sight, the RNIB, Eranda Trust, Hayman Trust, Moorfields Trustees, the Healing Fund, and the Michael and Ilse Katz Foundation, who have supported our glaucoma and ocular repair and regeneration research program. Without them newer safer techniques for surgery would not have been developed. Mr. Alan Lacey produced the diagrams. This chapter is dedicated to Ilse Katz who inspired and helped us to help others. The author has no financial interest in any of the products listed in this review including the instruments which he has designed.
REFERENCES
1.The Advanced Glaucoma Intervention Study (AGIS): 7. The relationship between control of intraocular pressure and visual field deterioration.The AGIS Investigators. Am J Ophthalmol 2000; 130(4):429 440.
2.Collaborative Normal Tension Glaucoma Study Group. The effectiveness of intraocular pres sure reduction in the treatment of normal tension glaucoma. Am J Ophthalmol 1998; 126(4):498 505.
3.Higginbotham EJ, Stevens RK, Musch DC, Karp KO, Lichter PR, Bergstrom TJ et al. Bleb related endophthalmitis after trabeculectomy with mitomycin C. 1996; 103(4):650 656.
4.Greenfield DS, Suner IJ, Miller MP, Kangas TA, Palmberg PF, Flynn HW. Endophthalmitis after filtering surgery with mitomycin. Arch Ophthalmol 1996; 114(8):943 949.
5.Khaw PT, Chang LPY. Antifibrotic agents in glaucoma surgery. In: Duker D, Yanoff M, eds.
Ophthalmology A Practical Textbook. London: Churchill Livingston, 2003.
6.Khaw PT, Occleston NL, Schultz GS, Grierson I, Sherwood MB, Larkin G. Activation and sup pression of fibroblast activity. Eye 1994; 8:188 195.
7.Khaw PT, Ward S, Porter A, Grierson I, Hitchings RA, Rice NSC. The long term effects of 5 fluorouracil and sodium butyrate on human Tenon’s fibroblasts. Invest Ophthalmol Vis Sci 1992; 33:2043 2052.
8.Khaw PT, Sherwood MB, MacKay SLD, Rossi MJ, Schultz G. 5 Minute treatments with fluorouracil, floxuridine and mitomycin have long term effects on human Tenon’s capsule fibroblasts. Arch Ophthalmol 1992; 110:1150 1154.
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9.Diestelhorst M, Grisanti S. Photodynamic therapy to control fibrosis in human glaucomatous eyes after trabeculectomy: a clinical pilot study. Arch Ophthalmol 2002; 120(2):130 134.
10.Siriwardena D, Khaw PT, King AJ, Donaldson ML, Overton BM, Migdal C et al. Human anti
transforming growth factor beta(2) monoclonal antibody a new modulator of wound healing in trabeculectomy: a randomized placebo controlled clinical study. Ophthalmology 2002; 109(3):427 431.
11.Wells AP, Cordeiro MF, Bunce C, Khaw PT. Cystic bleb formation and related complications in limbus versus fornix based conjunctival flaps in paediatric and young adult trabeculectomy with mitomycin C. Ophthalmology 2003; 110:2192 2197.
12.Khaw PT, Doyle JW, Sherwood MB, Grierson I, Schultz G, McGorray S. Prolonged localized tissue effects from 5 minute exposures to fluorouracil and mitomycin C. Arch Ophthalmol 1993; 111(2):263 267.
13.Occleston NL, Daniels JT, Tarnuzzer RW, Sethi KK, Alexander RA, Bhattacharya SS et al. Single exposures to antiproliferatives: long term effects on ocular fibroblast wound healing behavior. Invest Ophthalmol Vis Sci 1997; 38(10):1998 2007.
14.Daniels JT, Occleston NL, Crowston JG, Khaw PT. Effects of antimetabolite induced cellular growth arrest on fibroblast fibroblast interactions. Exp Eye Res 1999; 69(1):117 127.
15.El Sayyad F, Belmekki M, Helal M, Khalil M, El Hamzawey H, Hisham M. Simultaneous subconjunctival and subscleral mitomycin C application in trabeculectomy. Ophthalmology 2000; 107(2):298 301.
16.Wilkins MR, Occleston NL, Kotecha A, Waters L, Khaw PT. Sponge delivery variables and tissue levels of 5 fluorouracil. Br J Ophthalmol 2000; 84(1):92 97.
17.Wells AP, Bunce C, Khaw PT. Flap and suture manipulation after trabeculectomy with adjus table sutures: titration of flow intraocular pressure in guarded filtration surgery. J Glaucoma 2004; 13:400 406.
5
How to Do a Trabeculectomy
Clive Migdal
Western Eye Hospital, London, UK
Graham E. Trope
University of Toronto, Toronto Western Hospital, Toronto, Ontario, Canada
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Trabeculectomy is currently the most frequently performed surgical procedure for glaucoma. The modern trabeculectomy is a safe and effective procedure, with a high success rate. The chief aim is to allow aqueous to bypass the trabecular meshwork into the subconjunctival space, but at the same time, ensuring an optimum intraocular pressure (IOP) (i.e., not too high or too low) as well as maintaining the anatomy of the globe (i.e., preventing shallowing of the anterior chamber) (1,2).
It is important to assess each patient individually before undertaking trabeculectomy. Aiming for a target pressure specific for each individual eye should be an important consideration.
There are many different modifications of the trabeculectomy technique (3). To obtain optimum results, however, careful attention to detail at every step of the procedure is essential. In this way, outcomes can be improved and complications minimized. In general, everything possible to minimize fibroblast proliferation should be done, with as little tissue manipulation as possible.
1.TECHNIQUE
1.Selecting the site: All trabeculectomies should be sited superiorly (either centrally or superonasal or superotemporal). A superonasal or superotemporal quadrant site allows preservation of the adjacent superior quadrant for
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subsequent filtering or cataract surgery. Avoid the interpalpebral area as this predisposes to infection.
If the patient has had previous surgery that has involved the conjunctiva, choose a site where the conjunctiva is mobile, if possible.
2.Anesthesia: We prefer doing trabeculectomy surgery utilizing topical 2% xylocaine jelly (4); however, the procedure can be performed with subtenons/ subconjunctival anesthesia. We do not recommend retrobulbar, peribulbar, or general anesthesia unless there are specific indications for these. (See chapter on anesthesia for glaucoma surgery.)
3.Positioning the globe: A corneal traction suture allows the best positioning of the globe (Fig. 5.1). A superior rectus traction suture can also be used, but care must be taken not to put unnecessary traction on the muscle, which might cause damage, leaving the patient with a slight ptosis. Any hemorrhage in the area might also promote postoperative fibrosis, which is undesirable.
4.Conjunctival flap: The conjunctival flap can either be fornixor limbal-based (5,6). It is suggested that the success and safety of these two surgical approaches are similar.
A fornix-based flap is currently the most popular. Advantages include better exposure (allowing better visualization and easier forward dissection of the scleral flap), technically easier (less time and less bleeding, thus reducing fibrosis), a more diffuse bleb (as there is no posterior scar line to limit the bleb), less manipulation of the conjunctiva, easier wound closure, and less chance of buttonholing the conjunctiva. The main disadvantage of the fornix-based flap is the risk of postoperative wound leak at the limbus. This can be minimized with careful closure of the conjunctiva at the end of the operation.
Figure 5.1 Conjunctival flap.
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The limbal incision can either be linear, or with a relieving incision [Fig. 5.1(A) and (B)]. It is usually about 2’O clock hours in length. The incision is made through both the conjunctiva and the Tenon’s capsule, entering into the plane just above the sclera, and allowing separation of the conjunctiva and Tenon’s from the sclera. A small amount of oozing from the episcleral blood vessels usually stops spontaneously. Persistent bleeders should be individually cauterized using bipolar cautery.
If a limbal-based incision is used, make sure that the incision is sufficiently posterior to avoid overlying the scleral flap, as this may cause scarring/ walling off of the bleb. In addition, care must be taken not to damage the underlying superior rectus muscle.
5.Application of antimetabolites: This subject is covered in a separate chapter and therefore will not be discussed here.
6.Scleral flap: This can be either square, rectangular, or triangular in shape (1 in Fig. 5.2).
The size of the flap can vary. Most square flaps are 4 mm 4 mm, and rectangular 4 mm 2 mm. The flap is usually half scleral thickness.
After delineating the flap and performing the linear posterior incision, the flap is carefully dissected forwards, using an angled crescent blade. This is less sharp than a diamond knife, and thus avoids inadvertent perforation. It is necessary to follow a pathway parallel to the wall of the globe, thus maintaining a scleral flap of uniform thickness. As the flap is retracted, the underlying bed should have a white color similar to the surrounding sclera, although slightly grayer due to the underlying ciliary body. If it is very gray, the flap is too deep and the bed too thin. As the flap is dissected forward, a
Figure 5.2 Scleral flap, sclerostomy, and iridectomy.
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definitive white line is encountered, marking the anterior extent of the sclera. This lies approximately over the scleral spur, or the posterior extent of the trabecular meshwork. The grayish blue zone anterior to the white line is the oblique junction between the cornea and the sclera and overlies the trabecular meshwork. About 1 mm further forward, the bluish gray area gives way to the more translucent clear cornea. This junction corresponds approximately to Schwalbe’s line. The dissection is stopped when clear cornea is encountered.
Cautery should be kept to a minimum order to avoid promoting postoperative fibrosis.
Tip: Avoid extending the side cuts of the scleral flap too anteriorly. This will prevent excessive leakage immediately postoperatively, which risks causing hypotony and/or a flat anterior chamber.
7.Paracentesis: This is an essential part of the procedure and should be placed in the horizontal meridian.
Tip: Avoid incising into an eye with a very high IOP. The sudden decompression risks choroidal detachment or an expulsive hemorrhage.
If the IOP is .30 mm Hg preoperatively, consider administering mannitol, or other IOP reducing medications in order to reduce the IOP.
8.Sclerostomy: The sclerostomy incision should be at least 1 mm clear of either side of the scleral flap (Fig. 5.2).
After the initial linear incision into the anterior chamber, there are a number of different options for completing the sclerostomy: this can either be fashioned with a scleral punch (e.g., the Kelly Descemet’s membrane punch) (4 in Fig. 5.2), or a second parallel linear incision performed with the diamond knife, and the two then joined, enabling the removal of a block of scleral tissue (3 in Fig. 5.2). A fistula of 0.5 1 mm in height and 1.5 2 mm in width is created.
Tip: Ensure that a full-thickness block of scleral tissue is removed, and that Descemet’s membrane, which is transparent, does not remain.
9.Peripheral iridectomy: This is performed by grasping the peripheral iris through the sclerostomy with a fine-toothed forceps, then using a scissors (e.g., De Wecker’s) to excise a small portion of the iris (5 in Fig. 5.2).
Tip: Ensure that the peripheral and not central iris is gripped.
Holding the scissors blade in the horizontal meridian allows a wide v-shaped iridectomy, rather than a narrow one. The iridectomy should be visible through the clear cornea and the pupil should be round.
Should bleeding from the iris occur, instilling air into the anterior chamber at this point will stop the bleeding immediately and prevent a hyphema forming (this works via a tamponade effect). The air can be withdrawn through the paracentesis at the end of the procedure.
10.Closure of the scleral flap: This is done using various combinations of fixed and/or releasable sutures. Dr. Migdal’s preference is one fixed and one releasable suture using 10/0 monofilament nylon. Other methods include using
three 10/0 nylon sutures, one at each corner of the rectangular flap (or tip of the triangle) and one on each side, 1 2 mm from the limbus.
Tip: Always place the fixed suture first as manipulation of the flap for the second suture may loosen the first suture if this is of the releasable type.
The suture is placed at 458 across the angle of the flap. The suture should be rotated to bury the knot.