Surgical procedure

Essentially the surgery follows these steps:[7]

* Anesthesia
* Conjunctival peritomy
* Separation of the anterior Tenon’s fascia from the sclera
* Pass sutures through rectus muscles
* Rectus muscles disinserted from the globe
* Rotate and elevate the globe
* Open Tenon’s capsule to visualize optic nerve
* Cauterize necessary blood vessels
* Divide the nerve
* Remove the eye
* Hemostasis is achieved with either cautery or digital pressure.
* Insert orbital implant.
* If necessary (hydroxyapatite) cover the implant with wrapping material before
* Attach the muscle (if possible) either directly (PP) or indirectly (HA) to implant.
* Create fenerations in wrapping material if necessary
* For HA implants drill 1 mm holes as muscle insertion site
* Draw Tenon’s fascia over implant
* Close Tenon’s facia in one or two layers
* Suture conjunctiva
* Insert temporary ocular conformer until prosthesis is received (4–8 weeks later)
* After implant vascularization an optional secondary procedure can be done to place a couple peg or post.

Also under anesthesia

* Create conjunctival incision at the peg insertion site
* Create hole into implant to insert peg or post
* Modify prosthesis to receive peg/post.

The surgery is done under general anesthesia with the addition of extra subconjunctival and/or retrobulbar anesthetics injected locally in some cases. The following is a description of the surgical procedure performed by Custer et al.:[7]

The conjunctival peritomy is performed at the corneal limbus, preserving as much healthy tissue as possible. Anterior Tenon’s fascia is separated from the sclera. Blunt dissection in the four quadrants between the rectus muscles separates deep Tenon’s fascia.

Sutures may be passed through the rectus muscles before their disinsertion from the globe. Some surgeons also suture one or both oblique muscles. Traction sutures or clamps may be applied to the horizontal rectus muscle insertions to assist in rotating and elevating the globe during the ensuing dissection. Tenon’s capsule may be opened posteriorly to allow visualization of the optic nerve. The vortex veins and posterior ciliary vessels may be cauterized before dividing the nerve and removing the eye. Alternatively, the optic nerve may be localized with a clamp before transection. Hemostasis is achieved with either cautery or digital pressure.

The orbital implant is inserted at the time of enucleation. An appropriately sized implant should replace the volume of the globe and leave sufficient room for the ocular prosthesis. Enucleation implants are available in a variety of sizes that may be determined by using sizing implants or calculated by measuring globe volume or axial length of the contralateral eye.

In the past, spherical nonporous implants were placed in the intraconal space and the extraocular muscles were either left unattached or were tied over the implant. Wrapping these implants allows attachment of the muscles to the covering material, a technique that seems to improve implant movement and reduce the incidence of implant migration. Porous implants may be saturated with antibiotic solution before insertion. Because the brittle nature of hydroxyapatite prevents direct suturing of the muscles to the implant, these implants are usually covered with some form of wrapping material. The muscles are attached to the implant in a technique similar to that used for spherical non-porous implants. The muscles may be directly sutured to porous polyethylene implants either by passing the suture through the implant material or by using an implant with fabricated suture tunnels. Some surgeons also wrap porous polyethylene implants either to facilitate muscle attachment or to reduce the risk of implant exposure. A variety of wrapping materials have been used to cover porous implants, including polyglactin or polyglycolic acid mesh, heterologous tissue (bovine pericardium), homologous donor tissue (sclera, dermis), and autogenous tissue (fascia lata, temporalis fascia, posterior auricular muscle, rectus abdominis sheath). Fenestrations in the wrapping material are created at the insertion sites of the extraocular muscles, allowing the attached muscles to be in contact with the implant and improving implant vascularization. Drilling 1-mm holes into the implant at the muscle insertion sites is performed to facilitate vascularization of hydroxyapatite implants. Tenon’s fascia is drawn over the implant and closed in one or two layers. The conjunctiva is then sutured. A temporary ocular conformer is inserted at the completion of the pro- cedure and is worn until the patient receives a prosthesis 4 to 8 weeks after surgery. An elective secondary procedure is required to place the coupling peg or post in those patients who desire improved prosthetic motility. That procedure is usually delayed for at least 6 months after enucleation to allow time for implant vascularization. Technetium bone or gadolinium-enhanced magnetic resonance imaging scans are not now universally used, but they have been used to confirm vascularization before peg insertion. Under local anesthesia, a conjunctival incision is created at the peg insertion site. A hole is created into the porous implant to allow insertion of the peg or post. The prosthesis is then modified to receive the peg or post. Some surgeons have preplaced coupling posts in porous polyethylene implants at the time of enucleation. The post may spontaneously expose or is externalized in a later procedure via a conjunctival incision.