**4. Orbital implants**

Evisceration and enucleation result in an empty cavity and aesthetic problems for the patients that we should try to avoid. We must be sure that the patient fully understands the information given about the surgery and expected results in order to obtain the informed consent. Once this is done, the surgeon will decide the type of orbital implant, which can be placed primarily or secondarily in another surgery. The implant can be made of synthetic material, autologous material, or eye-banked tissues. The ocularist has a very important role in the aesthetics of the patient. Artificial eyes have enormously improved the psychological impact and the physical image of the person who undergoes this mutilating surgery. It was back in 1885 when Mules suggested the idea of placing orbital implants in these orbits [4]. Later on, Frost used hollow glass spheres as orbital implants. The surgical procedure was slightly modified with time. It was not until 1972 when Soll [19] suggested placing the implant beneath Tenon's capsule. Helveston covered the implant with donor sclera. The volume loss in some sockets, the presence of contracted sockets, or the implant extrusion made Smith and Petrelli propose the use of dermis-fat grafts in some patients. The ideal implant should fulfill these requirements: it should replace enough orbital volume, it should permit the artificial eye to move as much as possible, it should make the eye prosthesis fit adequately in the socket, it should have a low complication rate, it should be cost-effective and simple to implant in the orbit, biocompatible, and it should not degrade [20].

Herein, we will review the available types of implants. Bio-inert and nonporous materials have given way to porous materials. The latter have multiple micropores that are interconnected, mimicking the human bone trabecular meshwork. Complications after orbital implantation will depend on several factors, including the surgical technique, the material and size of the implant, previous orbital treatments (e.g., radiotherapy), orbital disease, poorly fitted artificial eyes, or infections.

#### **4.1. Implant selection**

Both evisceration and enucleation can be performed without orbital implants, but nowadays, it is very rare not to use them because of the very poor esthetic results. The goal of placing an implant in the orbit is to compensate the loss of volume, to improve the prosthesis motility, and to offer a good symmetry with the contralateral eye. Some considerations on these facts are as follows:

#### **4.2. Replacing volume loss**

Volume loss appears to be the main determinant of anatomic changes after enucleation [21]. Human radiographic studies have confirmed that placing a spherical implant within Tenon's capsule counteracts the rotation of intraorbital contents after enucleation and associated backtilt of the prosthesis. An adequate volume replacement permits a thinner prosthesis, relieving weight on the lower eyelid and minimizing associated ectropion formation and lid laxity [22]. Furthermore, an inferior displacement of the superior rectus-levator complex is associated to those changes [23]. Therefore, the implant must be big enough to replace the volume loss but not too big, which may create excessive tension on Tenon's capsule that could favor the implant extrusion.

Proper implant size can be calculated either preoperatively (from the axial length of the eye to be operated on or the fellow eye) or intraoperatively (determining the volume of fluid displaced by the enucleated eye in a graduated cylinder). We recommend the first option. Kaltreider et al. [24] showed that the implant diameter should be the eye's axial length minus 2 mm or minus 1 mm if the length was calculated with A-scan. An implant that is too small will need a bigger prosthesis, potentially resulting in lower eyelid laxity and malposition of the artificial eye. Larger than needed implants will require smaller prosthesis but are associated to higher exposure rates and may difficult the adaptation of the artificial eye [25]. We follow the recommendations from Jordan and Klapper for adult patients. These are 20-22 mm spherical implants in enucleation surgery and 18-20 mm spherical implants in evisceration surgery [16].

#### **4.3. Maintaining levator function**

**4. Orbital implants**

46 Advances in Eye Surgery

and it should not degrade [20].

eyes, or infections.

are as follows:

**4.1. Implant selection**

**4.2. Replacing volume loss**

Evisceration and enucleation result in an empty cavity and aesthetic problems for the patients that we should try to avoid. We must be sure that the patient fully understands the information given about the surgery and expected results in order to obtain the informed consent. Once this is done, the surgeon will decide the type of orbital implant, which can be placed primarily or secondarily in another surgery. The implant can be made of synthetic material, autologous material, or eye-banked tissues. The ocularist has a very important role in the aesthetics of the patient. Artificial eyes have enormously improved the psychological impact and the physical image of the person who undergoes this mutilating surgery. It was back in 1885 when Mules suggested the idea of placing orbital implants in these orbits [4]. Later on, Frost used hollow glass spheres as orbital implants. The surgical procedure was slightly modified with time. It was not until 1972 when Soll [19] suggested placing the implant beneath Tenon's capsule. Helveston covered the implant with donor sclera. The volume loss in some sockets, the presence of contracted sockets, or the implant extrusion made Smith and Petrelli propose the use of dermis-fat grafts in some patients. The ideal implant should fulfill these requirements: it should replace enough orbital volume, it should permit the artificial eye to move as much as possible, it should make the eye prosthesis fit adequately in the socket, it should have a low complication rate, it should be cost-effective and simple to implant in the orbit, biocompatible,

Herein, we will review the available types of implants. Bio-inert and nonporous materials have given way to porous materials. The latter have multiple micropores that are interconnected, mimicking the human bone trabecular meshwork. Complications after orbital implantation will depend on several factors, including the surgical technique, the material and size of the implant, previous orbital treatments (e.g., radiotherapy), orbital disease, poorly fitted artificial

Both evisceration and enucleation can be performed without orbital implants, but nowadays, it is very rare not to use them because of the very poor esthetic results. The goal of placing an implant in the orbit is to compensate the loss of volume, to improve the prosthesis motility, and to offer a good symmetry with the contralateral eye. Some considerations on these facts

Volume loss appears to be the main determinant of anatomic changes after enucleation [21]. Human radiographic studies have confirmed that placing a spherical implant within Tenon's capsule counteracts the rotation of intraorbital contents after enucleation and associated backtilt of the prosthesis. An adequate volume replacement permits a thinner prosthesis, relieving weight on the lower eyelid and minimizing associated ectropion formation and lid laxity [22]. Furthermore, an inferior displacement of the superior rectus-levator complex is associated to those changes [23]. Therefore, the implant must be big enough to replace the volume loss but

Another important issue to consider is the functionality of the levator muscle of the upper lid. The smaller diameter of implant, as compared to the globe alters the functional length and pivot point of the superior rectus-levator complex [26]. These factors may lead to a decreased levator function and ptosis. This situation can be improved either by surgery or by adding to the superior margin of the prosthesis additional material.

We should remember that with time, the orbital tissues of an anophthalmic orbit tend to contract towards the orbital apex, that is, nasally and inferiorly [27].

We can consider orbital implants in two main groups: integrated and nonintegrated implants.

#### **4.4. Nonintegrated implants**

They do not have a surface where rectus muscles can be anchored, nor they allow fibrovascular tissue to grow in them (this is why we call them nonintegrated). They include implants made of glass, rubber, iron, acrylic material, silicone, gold, silver, or polymethylmethacrylate [28]. Their only function is to replace the volume loss and to improve the cosmetic result. If the surgeon wants to increase the motility of the implant and, consequently, of the prosthesis, the rectus muscles should be repositioned and sutured to the anterior pole of the implant in order to move the artificial eye when the implant moves. Unfortunately, the movements achieved with this method are of smaller range than dose achieved when the implant is pegged. Some authors have suggested that when the rectus muscles are placed as described previously, that is, in the anterior pole of the implant, it may migrate when the muscles contract. Mourits et al. [29] consider that acrylic implants have a low extrusion rate and are easier to implant and explant (their surface is smoother, and there is no fibrovascular ingrowth to retain the implant) and are cheaper than porous implants. Nonintegrated implants have been widely used and have achieved good results in the end of the 19th century and all over the 20th century. Nowadays, they are still used in patients over 70 years old.

#### **4.5. Integrated implants**

#### *4.5.1. Hydroxyapatite*

Coralline hydroxyapatite is used frequently in enucleation surgery. It began to be used in orbitary implants in the 1980s. It is a calcium phosphate salt present in the human bone. It is considered to be nontoxic, nonallergenic, and biocompatible. It allows fibrovascular tissue to grow in the implant, thanks to its 3-D architecture [30]. If the fibrovascular growth is poor, there is a risk of implant extrusion. There are two commercially available implants: Bio-Eye (Integrated Orbital Implants, Inc., San Diego, CA) and M-Sphere (IOP, Inc., Costa Mesa, CA). Bio-eye has been the first choice for many surgeons for years. In a survey performed in 2002 with the oculoplastic surgeon members of the American Society of Ophthalmic Plastic and Reconstructive Surgeons (ASOPRS), they inquired about their preferences in primary enu‐ cleations; 27.3% used hydroxyapatite while 42.7% used porous polyethylene [31]. Jamell et al. [32] suggested that the best way to evaluate fibrovascular growth into the implant is contrastenhanced magnetic resonance with surface coil. They were able to show early fibrovascular growth in the implant being the central ingrowth of the fibrovascular tissue slower. This evaluation of the central vascularization of the implant is of great importance in order to know when to peg the implant. The greater vascularized the implant, the bigger the risk of blood when the implant is drilled, but at the same time, it is believed to reduce to the risk of infection, exposure, and migration [32,33]. Nevertheless, this technique has its drawbacks; it is time consuming and expensive. Therefore, sometimes you cannot detect complications of the vascularized implant on time. Due to this, Qi-hua et al. [34] used contrast-enhanced ultraso‐ nography (CEUS) as an alternative to evaluate the implant's vascularization, claiming it is also effective and it is cheaper than the contrast-enhanced MRI. In order to increase the vasculari‐ zation of the implant, some authors suggest to drill an additional number of holes in the implant where the scleral windows should be before inserting it in the cavity [35]. It is believed that increasing the fibrovascular ingrowth in the implant will decrease its risk of migration and extrusion. It should be emphasized that this type of implant is usually covered with donor sclera or other materials because its rough surface easily erodes the conjunctiva when the implant moves. This coating of the implant is useful to attach the extraocular muscles too. There is synthetic hydroxyapatite, which is half the price of coralline hydroxyapatite. It is easier to drill and to place the peg. There is also bovine hydroxyapatite from the cancellous bone of calf fibulae, fully deproteinized so as to be antigen-free.

When a peg is fit into the implant, this is done 6 or more months after the surgery because this is the time estimated for the vascularization to establish in the implant. This procedure is used in those patients who desire to increase the prosthesis motility.

Complications related to this type of implant are discharge, pyogenic granulomas, loss of the peg, reduced prosthesis motility, and an audible click, which can be annoying for the patient [36]. Calcified hydroxyapatite implants are capable of absorbing radiation. This is of special importance in children that have undergone enucleation surgery secondary to retinoblastoma, as it hinders local recurrences and decreases the effect of secondary orbital irradiation when needed [36-38]. Most patients are satisfied with the cosmetic outcome of the nonpegged implant and do not desire an additional procedure with increased risks for complications.

### *4.5.2. Porous Polyethylene (MEDPOR)*

It is made of synthetic, high-density polyethylene powder. It is flexible and easily moldable in order to adapt it to different shapes [39]. In contrast with hydroxyapatite, it is cheaper, it does not need to be wrapped because the rectus muscles can be tied to it, and it is easier to place in the orbit. Instead of using sutures, some authors have tried to fix the muscles to MEDPOR implants with 2-ocetyl-cyanoacrylate tissue glue [40]. This proof-concept study concluded that this technique seemed safe and had good functional and anatomical results. Porous polyethy‐ lene allows fibrovascular ingrowth, but this does not happen as fast as it does in hydroxya‐ patite. A major drawback of porous polyethylene was that there was no integrating device for the ocular prosthesis available. Shore [41] described a titanium postcoupling system that was included in the implant 6-12 months after the primary surgery. Generally speaking, these implants offer excellent motility, good tolerance, and very few complications. Timoney et al. [42] reported two cases of foreign body inflammatory giant cell reaction in patients who underwent orbital fracture repairs with porous polyethylene implants.

#### *4.5.3. Proplast*

**4.5. Integrated implants**

calf fibulae, fully deproteinized so as to be antigen-free.

in those patients who desire to increase the prosthesis motility.

Coralline hydroxyapatite is used frequently in enucleation surgery. It began to be used in orbitary implants in the 1980s. It is a calcium phosphate salt present in the human bone. It is considered to be nontoxic, nonallergenic, and biocompatible. It allows fibrovascular tissue to grow in the implant, thanks to its 3-D architecture [30]. If the fibrovascular growth is poor, there is a risk of implant extrusion. There are two commercially available implants: Bio-Eye (Integrated Orbital Implants, Inc., San Diego, CA) and M-Sphere (IOP, Inc., Costa Mesa, CA). Bio-eye has been the first choice for many surgeons for years. In a survey performed in 2002 with the oculoplastic surgeon members of the American Society of Ophthalmic Plastic and Reconstructive Surgeons (ASOPRS), they inquired about their preferences in primary enu‐ cleations; 27.3% used hydroxyapatite while 42.7% used porous polyethylene [31]. Jamell et al. [32] suggested that the best way to evaluate fibrovascular growth into the implant is contrastenhanced magnetic resonance with surface coil. They were able to show early fibrovascular growth in the implant being the central ingrowth of the fibrovascular tissue slower. This evaluation of the central vascularization of the implant is of great importance in order to know when to peg the implant. The greater vascularized the implant, the bigger the risk of blood when the implant is drilled, but at the same time, it is believed to reduce to the risk of infection, exposure, and migration [32,33]. Nevertheless, this technique has its drawbacks; it is time consuming and expensive. Therefore, sometimes you cannot detect complications of the vascularized implant on time. Due to this, Qi-hua et al. [34] used contrast-enhanced ultraso‐ nography (CEUS) as an alternative to evaluate the implant's vascularization, claiming it is also effective and it is cheaper than the contrast-enhanced MRI. In order to increase the vasculari‐ zation of the implant, some authors suggest to drill an additional number of holes in the implant where the scleral windows should be before inserting it in the cavity [35]. It is believed that increasing the fibrovascular ingrowth in the implant will decrease its risk of migration and extrusion. It should be emphasized that this type of implant is usually covered with donor sclera or other materials because its rough surface easily erodes the conjunctiva when the implant moves. This coating of the implant is useful to attach the extraocular muscles too. There is synthetic hydroxyapatite, which is half the price of coralline hydroxyapatite. It is easier to drill and to place the peg. There is also bovine hydroxyapatite from the cancellous bone of

When a peg is fit into the implant, this is done 6 or more months after the surgery because this is the time estimated for the vascularization to establish in the implant. This procedure is used

Complications related to this type of implant are discharge, pyogenic granulomas, loss of the peg, reduced prosthesis motility, and an audible click, which can be annoying for the patient [36]. Calcified hydroxyapatite implants are capable of absorbing radiation. This is of special importance in children that have undergone enucleation surgery secondary to retinoblastoma, as it hinders local recurrences and decreases the effect of secondary orbital irradiation when needed [36-38]. Most patients are satisfied with the cosmetic outcome of the nonpegged implant and do not desire an additional procedure with increased risks for complications.

*4.5.1. Hydroxyapatite*

48 Advances in Eye Surgery

This is an alloplastic, biologically inert porous material. It allows fibrovascular ingrowth and attachment of extraocular muscles.

#### *4.5.4. Aluminum oxide*

It is a porous ceramic bio-inert material, structurally strong, and free of contaminants. It is cheaper than hydroxyapatite, and its surface is smoother. It is too biocompatible and generates a very mild inflammatory response. It can also be wrapped in Vicryl (polyglactin 910) mesh.
