Over the past few decades, there have been numerous developments and refinements in synthetic implant material and design, implant wrapping, implant–prosthesis coupling, and socket volume considerations.6,10
The approach to optimizing the reconstructive outcome has allowed for improved lifelike qualities of the prostheses. The French military surgeon Ambroise Pare (1579) described the first in-socket prosthetic eye, which was made of metal and coated with paint and enamel.1 Venetian glass artisans produced the first glass eyes around the same period after they discovered a formula for material that could be tolerated within the eye socket.1,11 Although these early glass eyes were crude, uncomfortable, and very fragile, the “Venetian method” was considered the finest in the world. Their methods and materials were kept a secret until the eighteenth century. German doll maker Ludwig Muller-Uri’s invention of cryolite glass (a superior glass formula) in 1835 allowed for well-tolerated lifelike hollow glass eyes.11 After Muller-Uri refined the design of the artificial glass eye, Dutch ophthalmologist Snellen popularized its use throughout the Western hemisphere in the late 1890s. During World War II, cryolite glass, which was imported from Germany, became unavailable. With a large number of injured soldiers needing artificial eyes, the U.S. government began to search for a replacement material. Medical plastics were already being used in the dental field, and synthetic dental methylmethacrylate became a substitute for cryolite glass in the Americas.11 The standard technique for making a prosthesis from medical-grade acrylic plastic was developed in 1944 and is still used today throughout most of the developed world.
Epidemiology
In the majority of cases, eyes are removed by enucleation and evisceration rather than exenteration.12 The incidence of enucleation has been estimated at 2.8 persons per 100,000 in the population.13,14 Over the last several decades, a decrease in glaucoma-related enucleations has been reported.13,15,16 A shift from enucleations to eviscerations is also reported.15,17 The average age at the time of enucleation is approximately 50 years.18 The number of cases of eye removal is slightly higher in males than in females.18
Pathogenesis and Etiology
Indications for globe removal include tumors, end-stage glaucoma, trauma, infections, and other diseases resulting in blind, painful, and often disfigured eyes.12–17 Loss of eyes as a result of infections is more likely in developing nations compared with developed nations.19–21 Exenterations are most commonly performed for the treatment of malignant primary or secondary orbital tumors.22,23
Clinical Features
Removal of an eye may be necessary because of tumor, trauma, or end-stage ocular disease. Loss of binocular visual function with reduced peripheral field and loss of depth perception may result in difficulties with activities of daily living and impose various vocational restrictions.24–29 Individuals may experience a sense of facial disfigurement and poor self-esteem as a result of the “lost body part.”26,27,29 Because eye contact and facial appearance are an essential part of human interaction, it is important for the anophthalmic patient to maintain a natural, normal-appearing prosthetic eye.
Characteristics of the ideal anophthalmic socket include:2
1. A centrally placed, well-covered, buried implant of adequate volume, fabricated from a bioinert material that transmits motility from the implant to the overlying prosthesis
2. A socket lined with healthy conjunctiva and fornices deep enough to retain the prosthesis and permit horizontal and vertical excursion of the artificial eye
3. Normal eyelid and eyelash position, appearance, and tone
4. A supratarsal eyelid fold that is symmetric with that of the contralateral eyelid
5. A comfortable ocular prosthesis that looks similar to the sighted, contralateral globe and in the same horizontal plane
Currently, no surgical procedure satisfies all the above requirements. Over the past 2 decades, there have been numerous developments and refinements in anophthalmic socket surgery with respect to implant material and design, implant wrapping, implant-prosthesis coupling, and socket volume considerations. Successful anophthalmic surgery is achieved when the anophthalmic patient obtains a painless, noninflamed eye socket with adequate volume restoration and an artificial eye that looks and moves almost as naturally as a normal eye (Fig. 36.3).
Management
Enucleation
Enucleation involves removal of the entire globe while preserving other orbital tissues. The two primary indications include the presence of an intraocular malignancy or a blind painful eye with no view to the posterior pole and insufficient documentation of past ocular history.30 Enucleation may also be indicated in primary intraocular malignancies (e.g., melanoma or retinoblastoma) not amenable to alternative modes of therapy such as external radiation or brachytherapy.
Evisceration
Evisceration involves removal of the intraocular contents, leaving the sclera intact. It is typically performed with keratectomy. Posterior sclerotomies may facilitate insertion of a larger orbital implant.30–34
Controversy: The decision to perform evisceration rather than enucleation has given rise to controversy over the years.35 Dramatic relief from discomfort can be achieved with either technique. Since evisceration minimizes disruption of the sclera, Tenon capsule, extraocular muscle attachments, orbital connective tissue framework, and suspensory ligaments, it is a quicker, more straightforward technique for eye removal compared with enucleation and offers potentially better socket motility. Evisceration is contraindicated if a complete histopathologic examination of the globe and its contents is required.30 Ultrasonography, with or without computed tomography (CT), is performed before evisceration is considered in any eye in which the posterior segment cannot be adequately visualized. As antigenic uveal tissue may theoretically remain following evisceration, sympathetic ophthalmia is a potential sequela.36–38 Atrophic globes with minimal shrinkage may be candidates for evisceration. Globes with more advanced shrinkage may require a large posterior sclerotomy or a complete sclerotomy where the sclera is bisected.32 Severely phthisical eyes may not be amenable to evisceration.
Nonsurgical Management of the Blind, Painful Eye
For debilitated patients who have blind, painful eyes and are unable to undergo surgery and rehabilitation or psychologically not ready to have their eye removed, a retrobulbar injection of ethanol or chlorpromazine may provide adequate pain relief.39–41 Several reports have suggested that chlorpromazine produces superior pain control with fewer complications.40,42 Severe periorbital inflammation can result from retrobulbar chlorpromazine and may manifest as chemosis, proptosis, limited ocular motility, and facial swelling that may extend beyond the eyelids.42
A blind, disfigured, and shrunken globe, without significant discomfort and with no suspicion of an intraocular tumor, may be a candidate for a scleral shell (a thin ocular prosthesis that fits over the blind eye). The shell provides a natural appearance and allows the patient to retain the eye. If the globe is not shrunken, a scleral shell will frequently appear proptotic and may not be a good aesthetic option. A painted contact lens may occasionally be an alternative in these patients.
Controversies in Enucleation and Evisceration
Controversy: Historically, enucleation was considered within the first 10 to 14 days following severe globe trauma with extensive prolapse of uveal tissue because of concerns that the risks of sympathetic ophthalmia and harm to the remaining eye were thought to be greater than the likelihood of recovering useful vision in the traumatized eye.43 As sympathetic ophthalmia affecting the nontraumatized eye is rare and successful uveitis treatment is more common, prophylactic enucleation is now considered a questionable practice.30,36 Retention of the traumatized eye allows the patient to recover from the trauma and emotionally prepare for the removal, if needed, of the nonfunctional eye. If removal is not indicated, then the blind eye may provide a platform for an overlying prosthesis (scleral shell).
During evisceration surgery, it is theoretically impossible to remove all of the uveal tissue from the scleral shell. As a result, the risk for sympathetic ophthalmia exists.36–38 Dutton has reviewed the relative risk of sympathetic ophthalmia following evisceration and compared this risk with those of other ophthalmic surgeries and of other possible catastrophic life events.44 The relative risk of sympathetic ophthalmia following evisceration surgery is estimated to be 1 : 62,000 versus 1 : 1600 after vitrectomy surgery; i.e., a 40-fold increase in risk with vitrectomy, the more common ophthalmic procedure. The lifetime risk of dying as a result of a car accident (1 : 237), a plane crash (1 : 5051), drowning (1 : 9097), electrocution from an electric transmission line (1 : 39,042), or an attack by a wild animal (1 : 48,052) are all more common than the risk of sympathetic ophthalmia following evisceration. Thus, although the risk of sympathetic ophthalmia after evisceration is not zero, it is exceedingly small and most ophthalmologists will never see a case in their entire professional careers. Furthermore, unlike the more common events listed above, the rare case of sympathetic ophthalmia after evisceration may be successfully treated with corticosteroids or other immunosuppressive agents.
Orbital Implants
Secondary Orbital Implants
Orbital implant placement after enucleation or evisceration may not be a routine procedure in the health care delivery systems in the underdeveloped areas of the world. Additionally, in patients with incompletely treated endophthalmitis or panophthalmitis, implant placement may be delayed until the tissue swelling diminishes or the infection resolves. A “secondary implant” is one placed in the anophthalmic socket at a later date following the original enucleation or evisceration procedure. An orbital implant exchange is required in some sockets that already have an implant in position, and this, too, is considered a “secondary implant.” Implant exchange may be considered to improve motility, reposition a migrated implant, remove an exposed implant, increase orbital volume, or replace a porous implant suspected of causing significant socket inflammation or potentially harboring an infection.45
Current Classification of Implants and Terminology
Orbital implants can be classified as porous or nonporous; in either category, the implants are integrated, quasi-integrated, or nonintegrated, depending on how the implant is connected to the overlying prosthetic eye (Table 36.1).
Table 36.1
Terminology in Anophthalmic Socket Surgery
| Anophthalmic implant | Material or substance used to replace an enucleated or eviscerated globe (e.g., polmethylmethacrylate, silicone, hydroxyapatite, aluminum oxide, porous polyethylene, etc.) |
| Porous implant | An implant with numerous interconnected pores or channels throughout its structure that permit fibrovascular ingrowth (e.g., hydroxyapatite, aluminum oxide, porous polyethylene) |
| Nonporous implant | An implant that is solid and does not allow fibrovascular ingrowth (e.g., polymethylmethacrylate, silicone) |
| Prosthesis, prosthetic eye, artificial eye | A ceramic shell placed in the anophthalmic socket conjunctival fornices that is typically custom fabricated to look like the patient’s contralateral healthy eye to provide a symmetric ocular appearance |
| Scleral shell | A thin ocular prosthesis that fits over a nonpainful, blind atrophic eye (with or without shrinkage, i.e., phthisis) |
| Conformer | A clear shell (typically acrylic), with or without holes, placed over the closed bulbar conjunctival wound that extends into the conjunctival fornices behind the eyelids following implant placement in enucleation or evisceration surgery |
| Integrated implant | An implant that can be directly coupled to the overlying prosthetic eye with a peg system. As there is a small break in the overlying conjunctiva through which the peg protrudes, there is some debate whether this type of implant should also be referred to as a partially “exposed integrated implant” |
| Nonintegrated implant | An implant that has been placed within the anophthalmic socket that lacks a coupling mechanism to the overlying prosthetic eye. There is a closed, smooth, uninterrupted conjunctival surface completely covering the anophthalmic implant. Also known as a “buried nonintegrated implant” |
| Quasi-integrated implant | Refers to an implant that has been placed within the anophthalmic socket with a closed, uninterrupted conjunctival surface completely covering an anophthalmic implant that has an irregular anterior surface allowing indirect coupling (“quasi-integration”) of the implant to the overlying, modified prosthesis (e.g., Allen, Iowa, Universal, Durette, MEDPOR Quad implants). Also known as a “buried integrated implant” or an “indirectly integrated implant” |
| Secondary orbital implant | An orbital implant (of any type) that is placed into the anophthalmic socket at a time other than the initial enucleation or evisceration procedure |
| Peg | A motility coupling after enucleation, currently made of titanium, which permits direct coupling of the implant movement to an overlying prosthesis. Pegs may be inserted within sleeves that are drilled into the anterior aspect of the implant. There are also magnetic peg systems that remain within the implant and buried beneath the conjunctiva but coupled to the overlying prosthesis as a result of the magnetic components within the prosthetic eye and implant |
| Buried implant | An implant that has been placed within the anophthalmic socket with an overlying closed, smooth, uninterrupted conjunctival surface completely covering the implant |
| Exposed implant | An implant that does not have an overlying closed, smooth uninterrupted surface completely covering it |
Implant Selection
Controversy: Disagreement persists among orbital surgeons regarding the optimal orbital implant material and design.46 Surgeons have their own preferences regarding use of spherical versus shaped, wrapped versus unwrapped, and pegged versus unpegged implants. Cost, hospital budgets, and marketing pressures also play a role in implant selection. Pegged porous implants generally have the best overall prosthetic motility (Fig. 36.4). If a peg is not a consideration, the advantage of using a porous implant are diminished, as the prosthetic motility associated with a nonpegged porous orbital implant is similar to that of a nonporous spherical implant.47 However, the advantage of fibrovascular ingrowth and the smaller risk of implant migration remain reasons to consider using a porous implant even when pegging is not contemplated.48 A quasi-integrated implant (see Table 36.1) is an alternative that offers improved motility over a standard sphere but is technically more difficult to utilize (Fig. 36.5).49
A nonporous sphere that is wrapped, centered within the muscle cone, and attached to the rectus muscles is a reasonable choice if pegging is not a consideration and budgetary restraints limit the use of more expensive porous implants. In light of widespread disappointment with pegging of porous implants and no motility advantage without pegging, some surgeons think that more consideration should be given to placement of nonporous spheres that are less costly and perhaps more reliable.50
A nonporous implant inserted into the anophthalmic socket without a direct connection to the rectus muscles is the least desirable choice, in our view, as it offers minimal socket motility and the implants are prone to migrate, most commonly into the superotemporal space, which can make fitting of a custom artificial eye problematic.
An additional factor to consider in children undergoing eye removal is the need for further growth of the orbit. Eighty percent of adult orbital volume is reached around 5 years of age, with adult volume achieved by 12 to 14 years.51,52 Orbital soft tissue volume is a critical factor in continued orbital and facial bone growth, and thus adequate socket volume replacement following enucleation or evisceration surgery is important. The ocular prosthesis is also believed to be an important factor that helps minimize orbital growth retardation and prevent significant periorbital asymmetries following enucleation or evisceration.
Autogenous dermis-fat grafts are an alternative to the above implants in children under 5 years of age for volume replacement. These grafts may undergo hypertrophy and help stimulate orbital bone growth.53,54
Porous Orbital Implants for Enucleation or Evisceration Surgery
In an effort to design a biocompatible, integrated orbital implant, Perry introduced coralline (sea coral) hydroxyapatite (HA) spheres in 1985.55 HA implants represented a new generation of buried, integrated spheres with interconnecting pores that allowed host fibrovascular ingrowth (Fig. 36.6).56 By drilling into the HA implant, inserting a peg, and coupling the peg to the prosthetic eye, improved range of motion, as well as fine darting prosthetic eye movements, conferred a more lifelike quality to the artificial eye. Although HA implants represented a significant advance in anophthalmic surgery, experience with porous implants over the last 25 years has expanded our understanding of the limitations of HA and the other porous materials. Complications are not uncommon and include implant exposure, conjunctival thinning, socket discharge, pyogenic granuloma formation, implant infection, chronic pain, and a variety of peg problems.57–59
HA orbital spheres raised the costs associated with enucleation, evisceration, and secondary orbital implant procedures (US $600 versus $15–$50 for the more traditional silicone or polymethylmethacrylate spherical implants). Additional expenses associated with HA placement potentially include implant wrap material, assessment of implant vascularization with a confirmatory magnetic resonance imaging (MRI) study, a secondary drilling procedure with peg placement, and prosthesis modification. In the search for porous orbital implants with a reduced complication profile and diminished surgical and postoperative costs, numerous alternative implant materials have been introduced and include porous polyethylene, synthetic hydroxyapatite, other forms of HA implants, and an aluminum oxide ceramic implant .55–57,60 The costs of the alternative porous implants vary, but they are all less expensive than the Bio-Eye HA sphere. Long-term follow-up is important with any porous implant, as late complications (years after implantation) are known to occur.61,62
Anophthalmic Socket Volume Considerations
Insufficient volume replacement following enucleation or evisceration results in an abnormally deep superior sulcus, upper eyelid ptosis, enophthalmos, and lower eyelid malposition and may require a larger-than-desirable prosthesis (following enucleation socket syndrome or anophthalmic socket syndrome) (Fig. 36.7).63,64 The approximate implant volume may be estimated either preoperatively from the axial length of the eye or intraoperatively by determining the volume of fluid the enucleated eye displaces in a graduated cylinder.63–66 In most adults, 20- to 22-mm spherical implants are typically used following enucleation and 18- to 20-mm implants following evisceration. Implants with a diameter greater than 22 mm may have a higher exposure rate and hinder fitting of an acceptable custom prostheses.64,65 In pediatric patients, slightly smaller implants (16–18 mm) may be required, depending on the patient’s age and orbital development. Individualization of the implant size is important in optimizing orbital volume replacement and in achieving the best possible aesthetic result.60,61
Orbital Implant Wrapping
Controversy: Placement of HA or aluminum oxide (bioceramic) porous implants within the soft tissue of the eye socket is facilitated by smooth wrapping material, which diminishes tissue drag and facilitates precise fixation of the extraocular muscles to the implant surface.67 Implant wraps may also provide a barrier function over the spiculated porous implant surface and decrease the risk of exposure, although there is some debate as to whether exposure is truly minimized.67,68 Suggested advantages of placing unwrapped implants into the socket include simplification of the procedure, decreased operating room time, reduced cost, elimination of a second surgical site for harvesting an autogenous wrap, avoidance of a possible barrier to fibrovascular ingrowth, and decreased risk of disease transmission.67–69 Human donor sclera has historically been the first choice of implant wrapping material for most orbital surgeons.67 The use of human donor material, however, carries the potential risk of transmission of viruses or other pathogens.70 Several alternative wraps have become available over the last 2 decades and are outlined in Table 36.2 (Fig. 36.8).71,72
Table 36.2
Implant Wrapping Materials
| Available Implant Wraps | Comment |
| Specially processed human donor pericardium, fascia lata, sclera (Biodynamics International (U.S.) Inc., Tampa, FL) | Marketed as safe alternatives, convenience of a long (up to 5 years) shelf life, higher relative cost |
| Processed bovine pericardium (Peri-Guard or Ocu-Guard Supple, Bio Vascular Inc., Saint Paul, MN) | Although there have been only a few cases of bovine spongiform encephalopathy (BSE) in American cattle to date, there have been reports of infected cattle in Alberta, Canada, and the potential for prion transmission and BSE remains a concern71,72 |
| Autologous temporalis fascia, fascia lata, rectus abdominus sheath, after auricular muscle complex graft | Requires a second operative site, prolonged operative time |
| Microporous expanded polytetrafluoroethylene (e-PTFE) (Gore-Tex, W.L. Gore & Associates, Flagstaff, AZ), Polyester-urethane like e-PTFE | Complications (e.g., exposure, infection) with their use have made them undesirable71,72 |
| Polyglactin 910 mesh (Vicryl mesh, Ethicon, Somerville, NJ), Dexon mesh (style No. 8, nonstretch, medium-weight closed tricot, Davis & Geck, Manati, Peurto Rico) – bioabsorbable synthetic materials with a multiparous structure that allows fibrovascular ingrowth71,72 | Readily available, simple to use, eliminates the risk of infectious disease, does not require a second surgical site |
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