Chapter 147 Surgical Resection of Choroidal Melanoma
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Introduction
Successful exoresection of choroidal melanoma was reported as early as 19251; however, this type of operation is still performed only rarely, not least because of fears about its safety. Stallard reported two cases in 1966 and advocated partial choroidectomy only as a last resort for patients whose tumors did not regress after radiotherapy or who had poor vision in the fellow eye.2 In 1973, Foulds challenged the prevailing dogmas about radical surgery and started performing primary exoresection irrespective of the status of the fellow eye.3 Since then, we have between us performed more than 630 exoresections and 120 endoresections for posterior uveal melanoma.4–9 Others have also adopted these procedures.10–17 This chapter describes our surgical techniques, summarizes the results, identifies the main complications and their management, and discusses the indications in relation to other forms of conservative therapy. This overview reflects our own perspective, with reference to other literature on the subject.
Exoresection
Indications and contraindications
Tumors less than 6 mm in thickness respond satisfactorily to plaque or proton beam radiotherapy unless they have invaded retina or if they extend close to the optic disc. Radiotherapy of more bulky tumors is associated with a significant complication rate, which increases with time, regardless of the type of radiation used, especially when the tumor extends far anteriorly or posteriorly, or if there is an extensive retinal detachment.18–21 Conversely, large tumor size, anterior location, and the presence of exudative retinal detachment tend to make exoresection less difficult. Two matched group studies have reported that with large tumors, the results are better after exoresection than after iodine plaque radiotherapy.22,23
Relative contraindications to local resection include: (1) a tumor diameter >18 mm; (2) tumor extension to within a disc diameter of the optic disc margin; (3) extensive retinal invasion or any retinal perforation; (4) extraocular extension; (5) involvement of more than 2 clock-hours of ciliary body or angle; and (6) general health precluding hypotensive anesthesia. If, however, the patient has poor vision in the fellow eye or if enucleation is refused, then local resection can be performed, with special measures being taken to deal with the increased difficulty. Absolute contraindications include diffuse melanoma and optic nerve invasion. Old age is not in itself a contraindication and even facilitates the anesthesia, because hemorrhage is arrested at a higher blood pressure, which is also easier to control. It is possible to perform exoresection in children.24
Surgical technique
Exposure
The lashes are trimmed so that they do not get in the way during a delicate part of the operation. The eyelids are retracted using both a wire speculum and traction sutures. The ocular surface is kept moist with 1.5% methylcellulose solution. A 180° limbal conjunctival incision is made. The episclera is scraped away with a No. 15 Bard Parker scalpel. Intervening extraocular muscles are disinserted. Two bridle sutures (i.e., 5–0 braided polyester) for rotating the eye are inserted in the sclera 4 mm from the limbus and clipped with artery forceps (Fig. 147.1A). The tumor margins are identified by transillumination and marked on the sclera with a felt-tipped pen, with care being taken not to be mis-led by any penumbra or subretinal hematoma (Fig. 147.1B).
Lamellar scleral dissection
A lamellar scleral flap is fashioned and is hinged posteriorly. This is polyhedral, rather than circular, to facilitate good apposition of the wound edges during closure (Fig. 147.1C). The scleral flap should clear the apparent tumor margins by about 5 mm. By making the flap wider posteriorly, it is possible to reduce the length of the lateral incisions, making closure easier. The flap should be about 80% of the scleral thickness. Any inadvertent buttonholes in the superficial flap are immediately closed with a purse-string suture. Any buttonholes in the deep sclera are sutured or temporarily covered with a plastic patch to prevent prolapse of choroid or tumor when dissecting posterior sclera.
We prepare the flap using a feather blade for the initial scleral incisions and a Desmarres scarifier for lamellar scleral dissection (Fig. 147.1D).
To avoid troublesome hemorrhage, any vortex veins overlying the scleral flap are cauterized before being divided, applying bipolar diathermy both extraocularly (Fig. 147.1E) and to the intrascleral portion of the vein after cautiously exposing as much of the vessel as possible (Fig. 147.1F). Long ciliary vessels overlying the scleral flap are treated similarly. Gentle bipolar cautery of some of the short ciliary vessels adjacent to the optic nerve further reduces hemorrhage.
The lamellar scleral dissection should extend beyond the posterior tumor margin, which is located using the preoperative ultrasound measurements or by transillumination (Fig. 147.1G).
Ocular decompression
If the vitrectomy is delayed until the scleral flap is prepared, then three-port vitrectomy with infusion is unnecessary, the vitrectomy being performed through a single sclerotomy using illumination from the operating microscope (Fig. 147.1H).
Deep scleral incision
Two small buttonhole incisions are made in the deep sclera about 2 mm inside the superficial scleral incision anterolateral to the tumor (Fig. 147.1I). To avoid damaging choroid, the sclera is pinched with fine-toothed microforceps to create a fold, which is then shaved with a knife until perforation occurs. This scleral incision is extended around the tumor with blunt-tipped corneoscleral scissors (Fig. 147.1J,K). The deep scleral incision is kept 2 mm inside the superficial scleral incisions, so as to create a stepped wound edge, which facilitates subsequent closure (Fig. 147.1L). To prevent excessive bulging of the intraocular contents, the lateral and posterior scleral incisions are completed before the anterior incision is made.
Tumor excision
The subretinal space is entered, preferably at a site where the retina is known to be detached (Fig. 147.1M). This is done by holding the choroid with two pairs of ribbed (not toothed) microforceps and moving them apart to tear the uveal tissue.
Usually, the choroid is divided in front of the tumor (Fig. 147.1N), then laterally (Fig. 147.1O), and finally posteriorly, using blunt-tipped corneoscleral scissors. If there is excessive retinal bulging, further vitrectomy is performed, with the vitrector being viewed through the retina (Fig. 147.1P) or the pupil (Fig. 147.1Q). If ocular decompression is adequate, the retina should fall away from the tumor so that a space appears between the retina and the normal choroid around the tumor margins (Fig. 147.1R). This allows the uveal tissue posterior to the tumor to be divided with the corneoscleral scissors (Fig. 147.1S). Despite the systemic hypotension, there is usually some oozing of blood, which must be mopped away before clots form, because these are difficult to remove.
As soon as the tumor is excised, the instruments are exchanged for a fresh set to prevent possible seeding of tumor cells. At the earliest opportunity, the intravitreal pressure is increased until the retina bulges slightly in the scleral window so that there is no potential space in which a subretinal hematoma can form. This is achieved by exerting traction on the bridle sutures and by compressing the eye with sponges placed behind the eye posterior to the scleral window (Fig. 147.1T).
Scleral closure
The corners of the flap are sutured first, followed by the anterior margin and finally the lateral margins. Interrupted 8–0 nylon sutures are placed about 2 mm apart. As soon as the suturing of the flap is complete, the globe is reformed by injecting balanced salt solution intravitreally, either using the three-way tap, if an infusion cannula is present, or through a 25-gauge needle attached to a syringe (Fig. 147.1U). Gas tamponade is no longer considered useful, but 2 ml of air is kept in the syringe when injecting fluid, because its compressibility prevents a sudden rise in intraocular pressure, which might rupture the wound.
Adjunctive brachytherapy
Adjunctive plaque radiotherapy is routinely applied, delivering a dose of approximately 100 Gy to a depth of 1–2 mm. We favor the use of a 25-mm ruthenium plaque because of the limited range of beta irradiation, the convenience of a long half-life, and the thin shape of the implant, which facilitates positioning over the site of the previous tumor (Fig. 147.1V). If the superficial flap has inadvertently been buttonholed or if cyclectomy has been performed this brachytherapy is delayed by 1 month.
Eye closure
The muscles are resutured to their original insertions with 5–0 braided polyglycolic acid sutures (Fig. 147.1W). When the muscle insertion is located on the scleral flap, the reinsertion of the muscle is safer if a 1 mm stump of tendon is left in situ at the time of the disinsertion. To compensate for any muscle shortening, the distance from the suture knots to the limbus is measured before the muscle tendon is divided and also at the time of reinsertion so that a sling can be used if necessary.
The conjunctiva is closed with 8–0 braided polyglactin sutures (Fig. 147.1X). Antibiotics, mydriatics and steroids are given in the usual fashion. The entire procedure usually takes between 2 and 3 hours.
