Enucleation is the surgical procedure that involves removal of the entire globe and its contents, with preservation of all other periorbital and orbital structures. Enucleation exists in contrast to evisceration, in which the ocular contents are removed from an intact sclera, and exenteration, in which the entire orbital contents, including the globe and soft tissues, are removed.
The surgical removal of the eye was first reported in the 1500s as a procedure known as extirpation. Unlike an enucleation, the conjunctiva and extraocular muscles were not spared. By the mid 1800s, an enucleation without implant placement was described in the literature. The first reports of implant insertion following enucleation were described in 1886 and 1887, with variable success in implant retention.
The following are indications for enucleation:
- Intraocular malignancy or high suspicion for intraocular malignancy (most commonly uveal melanoma and retinoblastoma)
- Blind, painful eye
- Sympathetic ophthalmia
The role of primary enucleation in acute trauma remains controversial, particularly when a patient's mental status may be altered or he is unable to consent. Many surgeons advocate for primary closure of an open globe with later consideration for an enucleation if the eye remains no light perception or is severely disfigured. Enucleation of an eye can be associated with significant psychological trauma, and this approach provides the patient to consider his options and the pros and cons of enucleation after the initial trauma and any altered mental status has resolved and provides autonomy to elect this operation in the future. The risk of sympathetic ophthalmia in the uninvolved eye must be considered and discussed with the patient. In select cases where the eye is determined to have no visual potential, when repair or at least primary closure of the globe is determined to be impossible, and/or the medical comorbidities of the patient are significant, the surgeon may elect to perform primary enucleation.
In contrast to evisceration, enucleation allows for histologic examination of an intact globe and optic nerve. This is particularly important in settings of biopsy-proven or suspected intraocular malignancy, in which it is essential to determine the margins of the malignancy and invasion of the optic nerve, if any.
When comparing the aesthetics of an enucleated socket to an eviscerated socket, one retrospective study showed no statistically significant difference between enucleation and evisceration patients graded by both patients and masked observers.
Enucleation classically has been thought to decrease the risk of sympathetic ophthalmia as it avoids exposure to uveal antigens that may occur during an evisceration. However, more recent studies have reported no cases of sympathetic ophthalmia following evisceration.
A reduction in implant motility is often noted in enucleations. Compared to patients who underwent evisceration, one study found enucleation patients to have statistically significant poorer implant motility. However, no difference in prosthesis motility was noted between evisceration and enucleation patients.
In a 2003 survey of all board-certified ocularists in the United States, 92% reported preferring evisceration to enucleation for a patient who required removal of the eye. Eighty-two percent of survey respondents believed that evisceration afforded the best ocular motility and best overall cosmetic outcome, and 94% percent believed that complications of enophthalmos and/or deep superior sulcus were more common after enucleations.
An enucleation is performed as an outpatient procedure under general anesthesia. A retrobulbar block of local anesthetic with epinephrine is administered to aid in hemostasis and postoperative pain management. After a time-out is performed to confirm the correct operative eye with the entire operating room team, the face is prepared and draped in sterile fashion. A limbal conjunctival peritomy is performed with Wescott scissors for 360 degrees. Blunt dissection in the sub-Tenon's plane is then carried out in each of the oblique quadrants. Each rectus muscle is then identified, isolated with a muscle hook, secured with suture, and cut at the insertion to the globe. The superior and inferior oblique muscles are isolated and transected.
Once the globe is determined to rotate freely, the optic nerve is identified, strummed, and cut with enucleation scissors or an enucleation snare wire. Some surgeons prefer to first clamp the optic nerve with a curved hemostat prior to transection to encourage further hemostasis. An attempt should be made to cut a long segment of the optic nerve, particularly in situations of intraocular malignancy where histologic examination of the optic nerve is crucial. Additional hemostasis is then achieved with direct pressure in the intraconal space and cautery of the optic nerve if needed.
An implant is then placed in the intraconal space to replace volume lost by the enucleated globe, achieve cosmetic symmetry with the fellow socket, and allow for motility of the prosthesis. To determine appropriate diameter of the implant, use of the formula axial length-2 mm has been shown to provide for adequate replacement of lost volume and minimize superior sulcus deformity and enophthalmos.
In certain circumstances including severe infection, a surgeon may choose not to place an implant at the time of enucleation and elect to place an implant in a second surgery. A two-layered closure is then carried out with absorbable sutures, first of Tenon’s capsule and then of the conjunctiva. Antibiotic ointment is applied, a clear plastic conformer is placed over the closed conjunctiva, and a pressure patch is placed over the socket.
There are several types of implants that may be utilized in an enucleation. Implants are made in distinct sizes, and intraoperative selection of the appropriately sized implant is determined by the size of the patient’s orbit and the size of the implant necessary to achieve symmetry with the fellow eye. Implants may be porous or nonporous. Porous implants allow for anchoring of the extraocular muscles with proliferation of fibrovascular tissues into the implant itself. These include hydroxyapatite, porous polyethylene, and proplast.
Hydroxyapatite implants were first introduced in 1989. Because of their rough surface, they are typically wrapped with material such as donor sclera, acellular dermis, or pericardium. Additional wrapping materials include autologous tissue grafts, such as temporalis fascia or fascia lata and synthetic meshes. The extraocular muscles may be then sutured to the wrapping material for enhanced motility of the implant. Porous polyethylene implants were later developed as an alternative to hydroxyapatite. They have a smoother surface and do not require wrapping. Other advantages of porous polyethylene over hydroxyapatite implants include cheaper cost and ability to suture the extraocular muscles directly to the implant.
Implants may be pegged, in which a hole is drilled into the implant where a peg can be placed that attaches to the prosthesis. Pegging is typically performed six to twelve months postoperatively and allows for increased motility of the prosthesis. Compared to unpegged porous implants, pegged orbital implants were found in one study to produce a statistically significant improvement in horizontal but not vertical motility. Pegged implants were found to retain 87% of motility of the fellow eye while unpegged implants were found to retain only 50% of motility of the fellow eye.
In one series of 802 patients who underwent evisceration, enucleation, or placement of a secondary implant where a hydroxyapatite implant was used, 156 of 353 (44%) of patients with pegged implants had a complication. The most common complication in this series was peg extrusion in 20% of cases, which was shown to occur less frequently with titanium pegs as opposed to other types of pegs. In another retrospective series of patients with pegged hydroxyapatite implants, complications were noted in 38% (62/165) of patients. Complications of pegging included discharge (most common), pyogenic granulomas, loss of peg, poor transfer of movement, and audible click. Two patients (3%) had implant infection that required removal of the implant. Because of these complications, pegging has fallen out of favor and is now utilized less commonly.
Nonporous implants do not allow for proliferation of tissues into the implant. Therefore, they may have decreased motility and greater risk of implant migration. Types of nonporous implants include glass, silicone, acrylic, and polymethylmethacrylate (PMMA). The rectus muscles still may be sutured over the implant to impart motility to the implant and prosthesis.
In a survey published in 2004 of active members of the American Society of Ophthalmic Plastic and Reconstructive Surgery (ASOPRS) regarding management trends and preferences in primary enucleations and eviscerations, the most popular and commonly used implant was porous polyethylene in 43% of cases, followed by hydroxyapatite (27%) and nonporous implants (20%). The most commonly cited rationale for implant choice was outcome. Pegs were utilized in only 8% of cases. A majority of implants were not wrapped, but, of those that were, donor sclera was the most commonly utilized wrapping material.
Patients are typically patched for a brief period postoperatively and instructed to return to clinic one week after the procedure. Prescriptions are given for analgesics and antiemetics. Some surgeons also elect to prescribe prophylactic antibiotics.
Once the conjunctiva closure has healed, generally about 4-8 weeks postoperatively, patients are referred to an ocularist for fitting of an ocular prosthetic fitting. Patients will require regular follow up with both an oculoplastic surgeon and an ocularist to maintain the health of their socket.
Complications of an enucleation include the following:
- Removal of the wrong eye
- Damage to or loss of extraocular muscles
- Wound dehiscence
- Extrusion of the conformer
- Contraction of the fornices
- Exposure of the implant
- Extrusion of the implant
- Migration of the implant
- Hollow or deep superior sulcus
- Poorly fitting prosthesis
- Socket contracture
- Orbital cellulitis
Thank you to Oculoplastics Associates of Texas, Dallas, TX for providing article images.
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