Ординатура / Офтальмология / Английские материалы / Glaucoma Surgery_Trope_2005
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5.TECHNIQUES
Combined cataract with filtration surgery can be performed with varying techniques. The more commonly utilized techniques are
1.phacotrabeculectomy, one site,
2.phacotrabeculectomy, two sites,
3.scleral tunnel phacotrabeculectomy,
4.scleral tunnel ECCE (Blumenthal technique) with trabeculectomy,
5.combined nonpenetrating surgery, for example, phacoviscocanulostomy.
Other variations in technique include limbal vs. fornix based flaps; variations in suturing techniques such as suture-less and releasable suture technique; incision variations with scleral tunnels, smile incisions, large vs. small incisions; and the use of antimetabolites. In terms of IOP lowering, there is modest evidence to suggest that two-site phacotrabeculectomy achieves lower IOP than one-site surgery and combined surgery augmented with mitomycin-C (MMC) and not with 5-fluorouracil results in lower IOP (26). There is no evidence to suggest that fornixor limbal-based flaps influence the final IOP in phacotrabeculectomies (27 29). Presently, there is insufficient scientific evidence to recommend newer alternatives such as phacoemulsification combined with trabecular aspiration, viscocanalostomy, deep sclerectomy, endoscopic laser cycloablation, or trabeculectomy in the surgical management of coexisting cataract and glaucoma.
We will describe a standard one-site combined phacotrabeculectomy technique with releasable sutures, which we have used with good success for more than a decade, and a two-site procedure, which evidence-based analysis has shown to have some advantages in terms of long-term management of glaucoma over the one-site procedure (17).
6.OPERATIVE TECHNIQUE: ONE-SITE PHACOTRABECULECTOMY
1.Neurolept anesthesia is administered by an accompanying anesthesiologist. Topical 0.5% tetracaine is instilled.
2.A 0.5 cc of xylocaine 1% with epinephrine is injected in the sub-Tenon space of in upper right quadrant, as far superiorly as possible (for a right-handed surgeon).
3.Skin prep with 10% povidone iodine.
4.Lashes are draped.
5.The speculum is inserted.
6.A 8/0 silk corneal bridle suture is placed at the 11:30 o’clock position partial thickness through peripheral cornea.
7.A 158 blade is used to create a paracentesis at the 2 o’clock position.
8.At 11:30 o’clock, a fornix-based peritomy is performed, using a crescent blade and a nontoothed forceps, at the posterior limbus with the knife edge following the contor of the globe. Dissection under the conjunctiva and Tenon’s capsule is done with a Wescott scissors. The dissection is carried posteriorly into the upper right-handed quadrant in the space between the superior and medial (or lateral in the right eye) rectus muscle (Fig. 12.1).
9.If the Tenon capsule is very dense or fibrotic, a tenonectomy is performed, by excision with Wescott scissors. If MMC use is planned, the tenonectomy is usually omitted. Hemostasis of the vessels in the area of the planned scleral flap is done, using wet-field cautery. Vessels should be coagulated without
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Figure 12.1 Peritomy with the crescent blade at the limbus, following the contor of the globe.
charring of the underlying tissues. By applying cautery through a wet methylcellulose sponge, hemostasis without charring can usually be achieved. This technique decreases the amount of cautery energy applied directly to the tissues.
10.A Weck-cell soaked in 0.4 mg/mL of MMC is then applied. MMC is applied for 1 3 min, on the sclera where the scleral flap is planned and posteriorly under the conjunctiva and Tenon’s capsule. A narrow long pledget 2 4 mm is useful to direct the application posteriorly.
11.The scleral surface exposed to MMC is irrigated with 40 cc of BSS. This can be done by inserting the phacoemulsification probe under the conjunctiva and applying irrigation only.
12.Dissection of the scleral flap: A half-thickness rectangular flap of 3.5 4 mm is dissected, using a 0.12 forceps and a crescent-shaped knife held with the blade at 908 to the sclera to outline the flap. Take care to keep the same plane for the whole flap (Fig. 12.2).
Figure 12.2 Formation of the scleral flap.
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13.A standard scleral type dissection is done with the blade parallel to the surface directed anteriorly into clear cornea.
14.Enter the anterior chamber at the limbal base of the scleral flap with a 3.0 mm keratome.
15.Intra-ocular nonpreserved xylocaine 1% is injected, this being particularly important if iris manipulation is required.
16.Fill the anterior chamber with viscoelastic through the paracentesis.
17.In cases of small nondilating pupils, a pupil-widening procedure is performed, either with the use of iris hooks, or with flexible Grieshaber hooks. A bimanual maneuver with a cyclodialysis spatula in the left hand through the paracentesis incision and a Kuglin hook through the incision at 12 o’clock works well by dilating the pupil horizontally and vertically and is sufficient to increase lens exposure in most cases. In cases where the iris is floppy, thin, or iridoschisis is present, it is preferred to use flexible iris hooks to keep the iris dilated and away from the aspiration of the phacoemulsification handpiece.
18.Perform a circular curvilinear capsulorrhexis with a cystotome, and an Uttrata forceps. Vision blue enhancement of the anterior capsule can be used if needed. In patients with pseudoexfoliation, this maneuver should be done with extreme caution because of the weakened nature of the zonules in these patients.
19.Hydrodissection of the lens, with the 27 gage canula on a 2 cc syringe filled with BSS. Elevate the anterior capsule with the canula. Take care to mobilize the nucleus, while avoiding intra-operative capsular block or tears in the posterior capsule, by depressing the posterior lip of the operative wound while injecting steadily. This will allow the excess viscoelastics to be released from the eye, and eliminate pressure build-up which can potentially rupture the posterior capsule.
20.Phacoemulsification of the nucleus and its removal from the bag is performed with the surgeon’s bimanual phaco-chop technique of choice (Fig. 12.3).
Figure 12.3 Nuclear cracking during phacoemulsification. The phacoemulsification probe is inserted through the ostium for the trabeculectomy.
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21.Irrigation and aspiration (I/A) of the cortical remnants is then performed.
22.Polishing of the posterior capsule is performed if needed, with the automated I/A or manually with the hydrodissection needle. Digital pressure on the syringe will regulate the amount of vacuum applied, and allows for the gentle removal of cortical remnants.
23.Inject viscoelastic into the bag via the paracentesis wound, and reform the anterior chamber.
24.Insert a foldable intra-ocular lens with the technique varying with the type of lens and injector-tube used. We prefer an acrylic lens (Acrysof, SA60, Alcon, Fort Worth, TX) as it is nonreactive and has an excellent injector system.
25.Miochol is then injected via the paracentesis to constrict the pupil prior to the iridectomy.
26.With a 158 blade, the trabeculectomy is performed under the scleral flap by excising a rectangular 3 2 mm piece of tissue including trabecular meshwork. Radial incisions are made from posterior to anterior into the anterior chamber, with the trabeculectomy excision between these two radial incisions (Fig. 12.4).
27.A wide peripheral iridectomy is performed by grasping the peripheral iris tissue and exteriorizing it towards the trabeculostomy site, followed by cutting it with a De Wecker scissors parallel to the limbus. The base of the peripheral iridectomy should be slightly wider than the width of the scleral flap incision at the limbus to avoid iris incarceration in the ostium. Avoid excess traction on the iris and the ciliary body as this may cause hemorrhage or an excessively large iridectomy that can be visually disturbing.
28.Evacuate the intra-ocular viscoelastics using I/A through the main incision (Fig. 12.5).
29.Reform the anterior chamber with BSS via the paracentesis, as needed.
30.Suture the scleral flap with 3 4 interrupted buried 10/0 nylon sutures. The length of the bites should be relatively long, to make post-operative laser suture lysis easier to perform. Our preferred technique, however, is to utilize a “U”-shaped releasable suture (30). This technique is described elsewhere in this book. Pressure applied with a dry methyl-cellulose sponge over the scleral flap should not cause a leak. The function of the trabeculectomy
Figure 12.4 Trabeculectomy performed with a 158 blade.
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Figure 12.5 Conjunctival sutures with buried knots. Notice the loop of the releasable suture on the cornea (inverted U).
fistula is assessed by injecting BSS into the anterior chamber via the paracentesis checking for depth of the anterior chamber, the tension of the globe, and leakage of fluid across the scleral flap sutures.
31.The conjunctiva is then repositioned and closed with 10/0 nylon sutures in a water-tight manner. Two-wing sutures with bites through the peripheral cornea and one central horizontal mattress suture work best in our hands. Take extra care to burry all knots for patient comfort. Although closure with a continuous 8/0 vicryl is an option, we believe nylon causes less irritation than a braided absorbable suture with less tendency to suture erosion.
7.TWO-SITE PHACOTRABECULECTOMY TECHNIQUE
The phacoemulsification is performed through a clear corneal incision at the temporal limbus. We describe the technique for surgery on the right eye by a right-handed surgery.
1.The sites of the trabeculectomy and phacoemulsification are determined according to whether the eye operated upon is the right or the left, and on which hand the surgeon is used to holding the phaco-probe. For example, a right-handed surgeon operating on a right eye could make the trabeculectomy in the upper nasal or upper temporal quadrant and the phaco would be done through temporal clear cornea.
2.The trabeculectomy site is prepared to the point prior to entering the anterior chamber as described in the previous chapter or as described in the chapter on trabeculectomy.
3.The phacoemulsification site is prepared as follows: At the 9 o’clock position
(for the right-handed surgeon), a clear corneal incision is made with a 3.0 mm keratome. The tunnel is made in a self-sealing beveled fashion: the first part 908 to the corneal surface, than a section parallel to the corneal surface, till the whole anterior triangular part of the keratome is intra-corneal, then the posterior stroma and Descemet’s membrane are penetrated and the
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anterior chamber is entered. Phacoemulsification and intra-ocular lens implantation are completed. Viscoelastic is left in the anterior chamber.
4.The trabeculectomy is then completed.
5.The viscoelastic is removed from the anterior chamber and the corneal wound closed with one 10/0 nylon suture. At the end of surgery, there should be:
a.No leak from the trabeculectomy site.
b.The anterior chamber should be deep.
c.The eye should not be firm to palpation.
d.The bleb should easily be inflated by injection of BSS via the paracentesis site.
8.POSTOPERATIVE CARE
At the end of surgery, apply an antibiotic and steroid drops, and a protective shield. A patch is not needed as the lid function is normal owing to the absence of lid akinetic block (31).
Combined antibiotic and steroid eye-drops are commenced, instilled every 2 h, with a shield for protection on the day of surgery. The antibiotic is stopped on day 4, the steroid is tapered after 6 weeks. The patient is seen the following day when the visual acuity, the IOP, and the bleb are assessed. See other chapters in this book for postoperative management of filtration surgery.
9.COMMENTS
1.We do not recommend a tenonectomy when releasable sutures are employed, especially if MMC is used. If Tenon’s capsule is very hypertrophic or if laser suturelysis is planned, it can be excised.
2.Small pupils: Many techniques are available to mechanically dilate small pupils, such as iris stretching with hooks, Grieshaber flexible iris hooks, or sphincterotomies. Stretching results in small tears to the iris sphincter and enlargement of the pupil. Iris hooks are sometimes useful in patients with thin irides such as seen in nanophthalmic eyes or those with pale irides and in patients who have been on miotics for many years.
3.IOL types: Different IOLs exhibit different biocompatibility. Braga-Mele et al. reported that some types of silicone foldable lenses may prolong the inflammatory response after combined procedures compared with PMMA lenses (32). One study suggested that some acrylic lenses may be associated with IOP elevation, compared with silicone lenses (33). Acrylic lenses have a good record of biocompatibility, with a similar profile to PMMA lenses. The newer generation silicone
lenses may be more biocompatible and thus one may consider their use if the surgeon prefers, however the literature does not support this.
4. MMC The use of MMC enhances the success rate of the phacotrabeculectomy, especially in patients who have risk factors for failure (34,35). We routinely use MMC in phacotrabeculectomies, as the cataract surgery itself is a risk factor for failure. MMC use is also associated with a higher incidence of blebitis, wound leaks, and hypotony (36,37).
5.In our experience, flat chambers occur less commonly with phacotrabeculectomy, than with trabeculectomy, likely because of the support of the IOL and decrease in volume compared with the crystalline lens.
6.Avascular cystic blebs seem to occur less often after phacotrabeculectomy compared with trabeculectomy alone.
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10.TIPS
1.Hydrodissection should always be done carefully. Excess fluid must be allowed to egress by pressing the nucleus down a little, allowing fluid to escape from the bag into the anterior chamber and from there out of the eye through the incision. This avoids rupture of the posterior capsule. (The pseudoexfoliative capsule is especially prone to this.)
2.Phacoemulsification of the nucleus should be done using low vacuum, and 50% ultrasound, making short-deep grooves before cracking. This prevents interfering with the edge of capsulorrhexis and breaching the posterior capsule. It is important to make the groove deep rather than long to enable cracking of the nucleus. Leave sufficient lens material at the 6 o’clock position to enable grasping of the lens with aspiration and fragmentation with a chopper.
3.Should you suspect a rent in the posterior capsule, then visco-dissection may help stem the defect and prevent the downward movement of the nucleus. If the vitreous does prolapse into the anterior chamber, an anterior vitrectomy should be done protecting as much capsule as possible. If capsular support is adequate, a posterior chamber IOL can be placed in the bag or in the sulcus. The lens should be placed with the haptics at right angles to the rent so that the IOL will be stable and not enlarge the hole in the capsule. When placement in the capsular bag is impossible, the IOL should be placed in the sulcus. Make sure to switch to an appropriately sized lens for sulcus fixation. In those rare cases that the capsular support is entirely lacking, the IOL may need to be sutured trans-sclerally, as an AC lens may not be the best choice in POAG.
4.In the case of a nucleus dropped into the vitreous, do not chase it posteriorly. Resist the temptation to do a large vitrectomy through the anterior segment incision. Consult a vitreo-retinal surgeon, and have the nucleus retrieved from the vitreous. This should be done as soon as possible, but does not necessarily have to take place the same day. Extensive removal of the vitreous through the anterior segment can be dangerous and may result in retinal problems.
5.Pseudoexfoliation: The zonules in pseudoexfoliation are often unstable. They can be stabilized by use of an intra-capsular tension ring. Another technique of stabilizing the lens is using Grieshaber hooks that grasp the bag at the capsulorrhexis edge, together with the iris edge. The downside of this technique is that the hooks can cause shallowing of the anterior chamber, making manipulation more difficult.
6.Post-operative problems: Early post-operative pressure elevation is often related to retention of viscoelastics. Avoid release of scleral flap sutures at this time, as this may result in a flat anterior chamber with hypotony. Treat this IOP spike with ocular massage or a paracentesis.
11.COMPLICATIONS
See the relevant chapters on intra-operative, early, and late complications of filtration surgery.
Complications of cataract surgery: Intra-operative complications and methods to avoid them are mentioned in the technique section. Early postoperative complications include wound leak, increased IOP, IOL dislocation, and endophthalmitis. The major late complications of cataract surgery include endophthalmitis, cystoid macular edema,
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and retinal detachment.
1.Conjuntival wound leak: Can be treated by administering an aqueous suppressant and/or a bandage contact lens or by suturing the wound, if the wound edges dehisce. Most leaks around the sutures resolve within 48 h. We do not recommend a patch to manage this condition.
2.Early pressure spikes should be treated by digital massage and/or topical antiglaucoma medication. Sutures should not be removed early, as this may lead to shallowing of the anterior chamber.
3.Dislocation or malposition of the IOL. If there is capture of the IOL by the iris in the AC, then dilation of the pupil, with supine positioning of the patient, followed by pupil constriction with pilocarpine after the IOL has returned to its position is a good remedy to try. More severe dislocations of the lens usually need surgical intervention with repositioning with or without securing the lens with a suture through the iris or sclera.
4.Acute post-operative endophthalmitis is rare. This should be suspected if there is markedly decreased vision, pain, extraordinary anterior chamber reaction, and cellular reaction in the vitreous. See relevant chapter in this book for management of blebitis or endophthalmitis.
5.Cystic macular edema (CME) occurs in 1 2% of patients and is clinically relevant in 10% of these cases. CME should be treated with a course oral acetazolamide 125 250 mg TID QID, and topical NSAID, for a few weeks. Beware of using topical NSAID in a patient with dry eyes, or a connective tissue disease as this can lead to corneal melting.
6.Retinal detachment complicates 1 in 1000 cataract surgeries.
In summary, combined phacotrabeculectomy achieves shortand long-term pressure control in glaucoma patients undergoing cataract surgery. In our experience, there is a lower incidence of flat chambers after combined phacotrabeculectomy than after trabeculectomy alone. Ischemic and leaking blebs seem to be less common. Early post-operative pressure spikes are more easily controlled with combined phacotrabeculectomy compared with cataract surgery alone (1,38). Long-term pressure control is often better with combined phacotrabeculectomy than after cataract surgery alone (18,39,40). However, evidence suggests trabeculectomy alone probably achieves better long-term pressure control than combined phacotrabeculectomy (13 15).
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