Ординатура / Офтальмология / Английские материалы / Glaucoma Surgery_Trope_2005

dissection toward the limbus is carried across the surgical limbus for 0.5 mm exposing deep corneal lamellae.

5.3.Corneal-Scleral Trephining (73 to 103 Magnification)

A 1.5 mm trephine is used. The scleral flap is rotated forward using a #19 Hoskins forceps, exposing the surgical limbus and anterior corneal lamellae, and the trephine is placed so that one-third of the diameter of the trephine lies anterior to the surgical limbus in the corneal lamellae and two-thirds behind the surgical limbus in the sclera. The trephine is rotated alternately clockwise and anti-clockwise slowly. As the trephine proceeds, it is slightly tilted to the temporal side and careful watch is maintained for penetration of the AC on the temporal side. As the trephine enters the AC, there is a flow of aqueous humor from this area and the AC will shallow. Great care must be taken not to continue the trephining once the AC is perforated because of the danger of a collapsed AC, in which case the trephine may damage the anterior lens capsule, causing a traumatic cataract. The trephine is removed and trephine incision is completed using Vannas scissors. The trephine disk is then removed and a peripheral iridectomy is performed using a Hoskins forceps to pull iris through the opening in order to do the iridectomy. The conjunctivaTenon’s flap is then replaced and the conjunctival incision in the fornix is sutured, separately suturing Tenon’s capsule with #8/0 vicryl or #10/0 nylon continuous suture, and suturing the conjunctiva separately with a continuous #10/0 nylon suture.

6.SCLERECTOMY

The partially guarded subscleral Schei procedure and trephine are the most widely used full-thickness procedures at present. However, there are other types of sclerectomy that have been described, particularly in the first half of the 20th century. These have for the most part fallen into disuse.

6.1.Anterior Lip Sclerectomy

Anterior lip sclerectomy is performed using a conjunctival and 1/3 thickness scleral flap, exactly as described in the trephine and subscleral Scheie procedures. In this procedure, the 1/3 thickness scleral flap is rotated forward, exposing the surgical limbus area. An incision is made as described for subscleral Scheie procedure, 5 mm long and 1.5 mm behind the limbus, but no cautery is used. The incision is carried through into the AC using a diamond knife. Using a punch specially designed for the purpose, the sclera is punched out in the anterior lip of this incision, creating a fistula in the anterior lip of the scleral incision. Closure of the conjunctiva is performed in the same method as described for subsceral Scheie.

6.2.Posterior Lip Sclerectomy

This procedure is performed in exactly the same way as that described for anterior lip sclerectomy, except that the punch in this instance is used in the posterior lip of the sclerectomy, producing a fistula in the posterior lip of the scleral incision. Care must be taken not to punch into the ciliary body. As previously noted, the anterior lip sclerectomy and posterior lip sclerectomy are not widely used at this time.

REFERENCES

1.Cairns JE. Trabeculectomy preliminary report of a new method. Am J Ophthamol 1968; 66:673 679.

2.The AGIS Investigators. The advanced glaucoma intervention study (AGIS) VII: The relation ship between control of intraocular pressure and visual field deterioration. Am J Ophthalmol 2000; 130:429 440.

3.Greenfield DS, Suner IJ, Miller MP. Endophthalmitis after trabeculectomy with mitomycin C. Ophthalmology 1996; 103:650 656.

4.Higginbotham EJ, Stevens RK, Musch DC. Bleb related endophthalmitis after trabeculectomy with mitomycin C. Ophthalmology 1996; 103:650 656.

5.Soll DB. Intrascleral filtering procedure for glaucoma. Am J Ophthalmol 1973; 75:392 394.

6.Scheie HS. Retraction of scleral wound edges as a fistulizing procedure in glaucoma. Am J Ophthalmol 1958; 45:220 229.

7.Luntz MH, Harrison R, Schenker H. Glaucoma Surgery. Baltimore: Williams and Wilkins, 1984:84 90.

8.Elliot RH. Ophthalmoscope 1909; 7:804 807.

the specific surgical treatment, but today the increased use of the argon or YAG laser to create a hole in the iris (laser iridectomy) has largely replaced surgical iridectomy. In geographic areas where a laser is not available, surgical peripheral iridectomy is the only option. Some patients (e.g., Laplanders) have very thick irides, in which a laser has difficulty in penetrating, and in these patients surgical peripheral iridectomy is an option. Surgical peripheral iridectomy is performed under local anesthesia as an ambulatory operation.

2.SURGICAL TECHNIQUES FOR PERIPHERAL IRIDECTOMY FOR ANGLE CLOSURE GLAUCOMA

2.1.Mechanism of Action

Peripheral iridectomy is a safe surgical procedure and is highly successful. The objective is to create an opening for unhampered aqueous flow from the posterior to the anterior chamber, reducing the pressure build-up in the posterior chamber from relative pupil block, thereby allowing the iris to fall backward and open the angle. It is unnecessary to make the opening in the iris either basal or sector as long as the aqueous can flow freely through it.

The equalization of pressure between the posterior and the anterior chambers, following iridectomy, will separate the iris from the posterior corneal surface if the apposition has not become permanent. The effect of iridectomy on these irido-corneal attachments is to open localized areas of the angle where the closure is not permanent. The angle might only open adjacent to the iridectomy. This is due to loculation of the aqueous behind the iris as a result of widespread scar formation in the angle, limiting the free flow of aqueous. In these longstanding cases, it is useful to do two peripheral iridectomies, one in each superior quadrant, because this may reach more than one locule of aqueous and open more of the angle than would be achieved by only one iridectomy. Nevertheless, even in the earlier situation, one iridectomy, by equalizing anterior and posterior chamber pressures, will in most cases prevent further acute angle closure attacks. Any residual ocular hypertension after peripheral iridectomy is due to either chronic angle closure or an open angle mechanism (primary or secondary).

2.2.Surgical Techniques

Anesthesia: Topical anesthesia (alcaine-proparacaine hydrochloride 0.5% from Alcon) with intracameral preservative-free lidocaine 1% from Astra. Alternatively, the procedure can be performed using only topical 2% xylocaine jelly.

2.2.1.Surgical Incision (10 Magnification)

The operation is preferably performed through a corneal incision leaving the conjunctiva unmolested. A 3 mm long incision is made in the cornea just anterior to the limbus and at the anterior edge of the limbal corneal vessels.

The incision is best sited in the upper nasal quadrant using a #75 Beaver microblade. The corneal stroma is dissected down to Descemet’s membrane. At this point, the incision is grasped with Hoskin #28 forceps (Keeler) and, keeping the cornea pulled slightly upward and away from the iris, the anterior chamber is entered with the knife over the full 3 mm length of the incision (Fig. 11.1).

Figure 11.3 Surgical iridectomy.

A peripheral iredectomy results at the junction of the outer and middle third of the iris surface. This is the ideal position for the peripheral iridectomy because the major iris vessels are avoided.

2.3.Return of the Iris to Anterior Chamber

In most cases, the iris, once released, will slip back through the incision into the anterior chamber, and the peripheral iridectomy can be visualized through the cornea. In the event the iris becomes incarcerated in the incision, pressure on the scleral side of the incision with a flat iris spatula will generally dislodge it. Failing that, the cornea is stroked with an iris spatula from the center of the cornea upward to the limbus. When the iris still remains incarcerated in the incision, the two edges of the incision are held apart and a jet of balanced salt solution directed into the incision will dislodge the iris.

Once the iris is back in the anterior chamber, the surgeon should ascertain that the iridectomy included the pigment layer by demonstrating a red reflex through the iridectomy with retroillumination using the co-axial microscope light and also ensure that the pupil is round.

2.4.Suturing the Incision

One or two 10-0 nylon sutures are placed across the center of the corneal incision at full corneal depth and tied to provide good apposition but not too tightly. The sutures are cut on the knot which is buried on the corneal side of the incision. There is no necessity to reform the anterior chamber as it is not lost during the procedure. The surgeon also must ensure that the pupil is round.

Subconjunctival injection of antibiotics and steroids is unnecessary. An antibiotic steroid combination is used for a few days, postoperatively. The suture can be left indefinitely or removed after 3 months. Suture-induced astigmatism is minimal because of the small size of the incision. There is minimal postoperative uveitis or discomfort. An eye patch is not necessary.

3.RESULTS

Peripheral iridectomy is the most satisfying surgical procedure. When meticulous surgical technique is used, a patent iridectomy is always obtained, and this will cure .80% of primary angle closure glaucoma (3). Late cataract formation is the commonest complication. This may develop years later. Other complications are exceptionally rare but include wound leak, iritis, hyphema, malignant glaucoma, and endophthalmitis.

Failure to excise the pigment layer of the iris will result in a nonfunctioning iridectomy. This is readily corrected using bursts of an argon laser set at 50 mm, 0.5 W power, and 0.2 s exposure, which will remove the pigment layer.

4.PERIPHERAL IRIDECTOMY (ALTERNATIVE TECHNIQUE)

A conjunctival flap including Tenon’s fascia is made 4 mm from cornea and 5 mm in length. Incision into the anterior chamber is made for 3 mm with a diamond knife or #75 Beaver microblade. The incision line is in the mid-limbal position. A “knuckle” of iris is prolapsed by gentle pressure on the posterior lip. Full thickness iridectomy is performed with DeWecker scissors applied tangentially, the iris being grasped with #28 Hoskin forceps. Loose iris pigment is irrigated away. A single suture of 10-0 nylon is usually adequate to close the incision, which should be tested for watertight closure by pressing with the tip of a fine forceps. The conjunctival flap is closed with a short continuous 10-0 nylon suture. The anterior chamber is usually not lost but must be seen to be formed before allowing the patient to leave the operating room table. An antibiotic steroid combination is used for a few days, postoperatively.

5.COMPLICATIONS

Complications are few. There is a danger of injury to the ciliary body and hemorrhage if the limbal incision is made too far posteriorly. Failure to obtain a watertight closure of the incision can lead to a flat anterior chamber, and immediate surgical repair is mandatory. The other complications listed under peripheral iridectomy with a corneal incision can also occur.

6.RECURRENCE—ACUTE ANGLE CLOSURE

Acute angle closure may recur in the presence of a patent peripheral iridectomy in patients with plateau iris or a plateau iris component to a primary pupil block mechanism. Patients with this anomaly should be warned that there may be a recurrence. Plateau iris can be treated by combining peripheral iridectomy with laser gonioplasty.

REFERENCES

1.von Graefe A. Arch Ophthalmol 1869; 15:108, 228.

2.Curran EJ. Arch Ophthalmol 1920; 49:131.

3.Luntz MH. In: Turtz AL, ed. Ophthalmology. Vol. 1. Saint Louis, USA: The C.V. Mosby Company, Chapter 9, 1969:100.

with advanced optic nerve cupping or visual field loss (1,2). Phacotrabeculectomy is also beneficial in that it may reduce the long-term need for glaucoma medications (1,3).

2.OUTCOMES OF PHACOTRABECULECTOMY

Combined phacotrabeculectomy has been shown in several studies to result in long-term intra-ocular pressure reduction and improved vision (4,5). The visual success rates range between 62.5% and 98% (visual acuity better than 20/40). Pressure control without medication ranges between 66% and 96% (5 12). Evidence, however, suggests that trabeculectomy alone achieves better long-term pressure control than combined phacotrabeculectomy (13 18). This has led some surgeons to advocate a two-step approach, surgically controlling pressure first, followed later by phacoemulsification. The effect on bleb function and IOP of subsequent cataract surgery in the presence of a filtering bleb is debatable. Several published studies have reported failure rates (usually defined as the need for additional glaucoma medication or further filtration surgery) of 0 33%, 15 24 months following phacoemulsification in a previously filtered eye (19 25). These studies were mostly retrospective. Two of these (19,23) compared the success rate with matched control groups of trabeculectomy only, and did not find a statistically significant difference suggesting that the failure rate of filtration following subsequent phacoemulsification may be the same as the natural course of a trabeculectomy.

3.CONTRA-INDICATIONS

In certain circumstances, combined procedures should not be performed:

1.If the lens opacity is not significantly affecting vision, or likely to do so soon.

2.When the optic nerve is healthy and the pressure well controlled on one or two medications.

3.When glaucoma surgery is likely to fail because of bleb fibrosis, for example, neovascular glaucoma.

4.PATIENT INFORMATION AND INFORMED CONSENT

The patient should be informed that the goal of surgery is to improve vision by cataract surgery and to gain better short and possibly long-term control of IOP. The patient should be told that surgery may not free them indefinitely from use of medication or possible future glaucoma surgery to control pressure. The patient should be made aware that the filtration procedure will not cure the glaucoma or reverse existing visual field loss. Together with the usual consent information pertaining to possible complications from cataract surgery, the patient should also be informed about the issues relating to filtration surgery such as the need for digital massage or suture removal or lysis, anterior chamber reformation, bleb problems including infection, and the increased risk of choroidal hemorrhage, along with the expected fluctuation in visual acuity that accompanies such interventions. It is important that patients are made aware that visual recovery is usually slower than that experienced after phacoemulsification alone and good vision is not expected for 2 6 weeks after surgery. Post-operative visual acuity can be influenced by astigmatism induced by the operative wound and sutures.