Enucleation for Choroidal Melanomas

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Chapter 144 Enucleation for Choroidal Melanomas

Julian D. Perry, Arun D. Singh, Milap P. Mehta

Introduction

Approximately 5% of all melanomas occur in the eye and surrounding adnexal structures and 85% of these are uveal in origin.¹ Uveal melanomas are the most common primary intraocular malignant tumor.² According to one report, the overall incidence of uveal melanomas is 5.1 per million and 80–90% of uveal melanomas involve the choroid.³

Over 30 years ago, Zimmerman investigated the benefit of enucleation in eyes with choroidal melanoma.⁴ He observed a peak in mortality 2–3 years after enucleation and suggested that the rise of post-enucleation mortality was a direct result of the enucleation.⁴ This controversy led to the trend away from enucleation towards vision and eye-sparing treatments. Subsequent studies have demonstrated that the observed post-enucleation rise in mortality was a reflection of natural history of the primary tumor and its metastases rather than direct effects of enucleation causing iatrogenic tumor seeding. Metastasis was independent of the method of treatment.⁵

For the treatment of the primary tumor, there are many therapeutic options such as observation, transpupillary thermotherapy, plaque radiotherapy, local resection, and enucleation.² In the USA, the two most frequently used methods of treatment are plaque radiotherapy and enucleation.² The COMS demonstrated no statistical difference in all-cause mortality between the brachytherapy and enucleation arms in either medium or large choroidal melanomas.⁶

As mortality data show, no significant difference between enucleation and brachytherapy, quality-of-life (QOL) measurements become important in deciding on a therapeutic plan. The Collaborative Ocular Melanoma Study (COMS) ascertained QOL measures of driving difficulties, near vision activities, activities requiring stereopsis, anxiety levels, and depression levels.⁷ Patients reported higher levels of function for driving and peripheral vision in the brachytherapy arm compared to the enucleation arm for the first 2 years post-treatment but these differences diminished 3–5 years post-treatment.⁷ Patients in the brachytherapy arm also had more symptoms of anxiety after treatment compared with the enucleation group.⁷ Enucleation still remains a viable treatment option for choroidal melanoma in the proper setting.

The COMS group demonstrated a cumulative metastasis rate of 25% at 5 years and 34% at 10 years.⁸ Once metastasis occurs, the median survival time is 3.6 months, and death is inevitable as there are no effective treatment options at present.^8,⁹

Purpose of enucleation

Enucleation should remove malignancy with clear margins and restore cosmesis by allowing for the comfortable use of an ocular prosthesis coupled to an underlying orbital implant.

Indications

The main indications for primary enucleation are large tumor size, neovascular glaucoma, optic nerve invasion, blind painful eye, localized extrascleral extension, and patient preference. Enucleation is also considered for the treatment of medium-sized choroidal melanoma with poor vision (<20/400) or absence of potential for visual recovery. Functional status of the other eye and patient preference are also important considerations in the decision-making process. The indications for secondary enucleation are local treatment failure and ocular pain secondary to radiation-related complications.

Implant description

An ideal implant should restore volume, transmit motility, possess a low complication rate, and demonstrate cost-effectiveness.¹⁰ To transmit motility, the extraocular muscles should attach to the implant directly or surround the implant indirectly.¹⁰ An implant of proper size restores volume.¹¹ Current orbital implant designs fall into two general categories: solid spheres and porous, integrated implants. Solid spheres include silicone and polymethyl methacrylate (PMMA), while porous implants include coralline hydroxyapatite and porous polyethylene.¹⁰ Bioceramic and other implants also exist.¹⁰ Porous materials allow for fibrovascular ingrowth which may induce epithelialization of a drill hole to accept a prosthesis coupling peg to improve motility. Pegged hydroxyapatite implants offer subjective improved motility over unpegged implants and vascular ingrowth possesses some theoretical advantages, including decreased rates of infection, exposure, and extrusion.^10,¹²

Coralline hydroxyapatite (HA) is a porous, nontoxic implant composed of inorganic, nonreplenishable marine coral.¹³ High-density porous polyethylene is a porous, synthetic implant that can be molded into various shapes.¹⁴ Hydroxyapatite has a brittle nature, which precludes direct suturing to the implant surface.¹⁵ Pore sizes and interconnectivity vary, which could affect vascularization.¹⁶ Some surgeons drill holes into porous implants to facilitate integration.¹⁷ The use of porous materials adds additional costs of the implant, wrapping material, and imaging studies, and possesses higher complication rates.¹⁸

Some surgeons wrap porous implants to protect the anterior tissues from hydroxyapatite bone spicules and to facilitate muscle attachment and implantation. However the perceived benefits have not been proven.¹⁵ Wrapping materials include donor sclera, autogenous fascia or polyglycolic acid mesh. While some surgeons wrap porous polyethylene implants, the extraocular muscles can be directly sutured to polyethylene.^19,²⁰ Wrapping materials may pose infection risk and decrease vascularization rates.¹⁷

When surveyed in 1995, the majority (56%) of the American Society of Ophthalmic Plastic and Reconstructive Surgeons (ASOPRS) preferred hydroxyapatite implants and human donor sclera wrapping in enucleations.²¹ When resurveyed in 2002, the majority (43%) of ASOPRS surgeons preferred porous polyethylene and only 27% preferred hydroxyapatite.¹⁸ In the later survey, most implants (60%) were not wrapped and only 25% were wrapped in human donor sclera.¹⁸ The majority (92%) of implants were left unpegged.¹⁸ In 2007, a survey from the UK supported these trends, demonstrating that 55% of surgeons used porous implants, 57% wrapped the implant (with autogenous sclera being most popular; 20%), and only 7% pegged the implants.²² Custer demonstrated no significant difference in motility between unpegged hydroxyapatite and solid implants.²³ The potential advantages of using porous implants and wrapping materials should be weighed against the risks, morbidity, and additional cost.²⁰ If the surgeon does not plan to peg, if the patient has systemic illnesses or factors that may limit fibrovascular ingrowth, or if a porous implant may not improve a patient’s quality of life, the surgeon should give consideration to a solid implant.

Implant sizing

Proper implant sizing is essential for cosmesis, volume restoration, and to minimize extrusion, exposure, and sulcus deformities. Most adult patients require at least a 20 mm implant. Traditionally, surgeons use a set of sizing spheres to individualize implant size and use standard volume tables to maximize volume restoration. Alternatively, orbital implant size can be determined using the contralateral eye axial length measurements subtracted by 2 mm, or by 3 mm for hyperopia.¹¹ Another algorithm subtracts the volume of an ideal 24 mm eye by the volume of sclera and 2 mL to determine implant volume.²⁴

Enucleation technique

Enucleation techniques vary but all employ certain principles. Enucleation is usually performed under general anesthesia. However, local anesthesia with monitored anesthesia care can also be used in conjunction with a supraorbital nerve, an infraorbital nerve, and a modified van Lint block. In either case, analgesia and improved hemostasis may be achieved with a retrobulbar or peribulbar block consisting of 3–4 mL of 1% lidocaine with 1 : 100 000 epinephrine and 8.4% sodium bicarbonate in a 1 : 10 ratio with 50 units per 10 mL of hyaluronidase. An additional 1 mL of the same solution is injected subconjunctivally. The surgeon must avoid penetration or perforation of the eye with the needle.

The authors’ technique is as follows: A 360° peritomy is created with blunt Westcott scissors. Conjunctiva and the Tenon layer are dissected from underlying sclera using Stevens scissors (Fig. 144.1). The Stevens scissors are used to bluntly dissect in each oblique quadrant (Fig. 144.2) and each rectus muscle is isolated on a muscle hook. The Tenon layer attachments to the rectus muscles are stripped and the muscle is secured on a double armed 6–0 polyglactin 910 suture through its insertion. Each muscle is disinserted from the globe using blunt Westcott scissors or Abley scissors (Fig. 144.3).

Fig. 144.1 A 360° peritomy is performed using blunt Westcott scissors.

Fig. 144.2 Stevens scissors are used to bluntly dissect into each oblique quadrant.

Fig. 144.3 Each rectus muscle is isolated on a muscle hook, secured using 6-0 polyglactin suture, and disinserted using blunt Westcott scissors or Abley scissors.

The inferior oblique muscle insertion is identified and isolated with a muscle hook in the inferotemporal quadrant. To minimize bleeding, the inferior oblique muscle is cauterized prior to transection. The superior oblique muscle is then identified in the superomedial quadrant and cut.

A muscle hook is swept against the globe to identify any remaining attachments that require lysis and a rent is created in the posterior Tenon layer using Stevens scissors. To maintain hemostasis, the optic nerve may be clamped with a long curved hemostat. The hemostat is inserted with the blades closed to palpate and strum the optic nerve prior to clamping. A second hemostat or locking toothed forceps is placed over the medial rectus muscle stump to assist in elevating the globe. The optic nerve is transected using enucleation scissors, and the globe is removed using the hemostat or forceps on the medial rectus stump. The optic nerve stump is cauterized with the bipolar cautery unit under direct visualization using malleable retractors.

The orbital implant is placed using an injector or periosteal elevators with modest posterior digital pressure. If the implant is wrapped, then four windows can be created just posterior to the rectus muscle attachments. If a wrapping material is not employed, the muscles are sutured directly to or over the implant. Direct attachment of the vertical recti muscles to each other may lead to fornix insufficiency. We suture each rectus muscle to the adjacent rectus muscle suture using a 4–0 polyglactin 910 suture to create a physiologic attachment of the extraocular muscles over the implant with a diameter of approximately 10 mm (Fig. 144.4). The anterior Tenon layer is closed using a running 4–0 polyglactin 910 suture (Fig. 144.5). Finally, the conjunctiva is closed using a running 6–0 plain gut suture (Fig. 144.6).

Fig. 144.4 A suitable-sized implant is placed using an injector or periosteal elevators and the muscular attachments are sutured onto the implant.

Fig. 144.5 Tenon layer is closed in running fashion.

Fig. 144.6 The conjunctiva is sutured in running fashion, creating a multilayered closure.

Antibiotic ointment and a small plastic conformer are placed into the socket and the eyelids are sutured closed using a 6–0 Prolene suture. A pressure patch is placed for one week.

Special considerations

Optic nerve invasion and limited extrascleral extension

Overall, choroidal melanoma rarely invades the optic nerve.²⁵ The COMS demonstrated extrascleral extension in only 8.2% of 1527 enucleated eyes.²⁶ Limited extrascleral extension does not contraindicate enucleation. However, the approach to the optic nerve transaction may have to be modified if there is evidence of limited extrascleral extension. Limited extrascleral extension may be suspected based on echographic or radiologic imaging.²⁷ It is recommended that the quadrant opposite to the extrascleral extension be used to introduce the enucleation scissors so as to avoid transecting the extrascleral extension. In some cases, greater access to the posterior orbit may be obtained via lateral orbitotomy approach to transect the optic nerve and for en bloc removal of the extrascleral extension.^28,²⁹

Complications

Complications of enucleation are rare and include pyogenic granuloma, conjunctival inclusion cyst formation, conjunctival wound dehiscence causing exposure or extrusion, implant displacement or migration, infection, orbital hemorrhage, socket contracture, and ptosis.^18,³⁰ In the COMS large tumor trial, patients who received pre-enucleation radiation had an overall complication rate of 8% and patients who had not received radiation had a complication rate of 4%.³⁰

Additional complications of pegged implants include peg malposition, peg cracking, and an audible peg click.¹⁸ Reports on overall complication rates vary widely for porous and nonporous implants and for pegged and unpegged implants. However, general trends among the various implant choices exist.

Nunery et al. demonstrated a higher exposure rate in HA versus silicone implants.^31,³² Exposed porous implants may not extrude as often as solid implants because of fibrovascular ingrowth, but nearly all exposures ultimately require repair.³¹ Exposure rates range from 0% to 33.3% for porous implants.^13,³³^–³⁹ The American Society of Ophthalmic Plastic and Reconstructive Surgery (ASOPRS) survey revealed an exposure rate of only 3% with the majority (81 of 82) of events occurring with porous implants rather than solid implants.¹⁸ A meta-analysis of exposure rates of all implants demonstrated a 1.3% (2/153 cases) rate with silicone, a 4.9% rate (96/1959 cases) with coralline hydroxyapatite, and an 8.1% rate (41/507 events) with porous polyethylene.³⁴ For pegged implants, all complication rates are greater, including pyogenic granuloma formation (14%), exposure (6%), infection (5%), and peg malposition (5%).¹⁸