When an eye is removed, an orbital implant is recommended to replace the lost volume.
An implant is usually ball shaped and made of synthetic material. Usually it is placed during enucleation surgery (primary implantation), but can be surgically placed later (secondary implantation).
Orbital implants fill space previously occupied by the eye. Muscles are usually surgically attached so it can move under the artificial eye.
The implant is buried under pink tissue (conjunctiva) lining the socket, and stays there permanently, unless it becomes exposed or infected.
Sockets with an implant grow better than without. However, orbital growth, with or without implant, usually lags behind an orbit with a real eye.
Migration of the Implant
Over time, orbital fat moves down and forward in an enucleated socket, so the implant may also move down and forward. This causes shallowing of the gap behind the lower eyelid (lower fornix), and deepening of the gap behind the upper eyelid (sulcus).
The implant can also migrate deeper into the orbit, resulting in reduced volume and movement.
When migration occurs fitting the artificial eye can becomet difficult. The ocularist (person who makes artificial eyes) can add bulk to the upper half of the artificial eye to compensate for these changes. Occasionally, surgery may be needed to replace the volume.
A tear in the surgery scar or breakdown of tissues overlying the implant may result in exposure of the implant. This provides an entry point for bacteria that can infect the implant.
The typical signs of implant infection are:
- The implant is visible, appearing white in against healthy pink tissues.
- Blood tinged or yellow discharge
- Foul smelling discharge
A break in conjunctiva can repair itself, but this can take several weeks or months. Antibiotic drops prevent and/or treat infection while the exposed implant heals. Infections are difficult to eradicate, and prevention is key.
Replacing the Implant
A healthy covered implant does not need replacing. Volume deficiency can be resolved with orbital floor wedge implants or injectable fillers.
The implant should be replaced when there is recurrent, long standing or extensive exposure, or infection does not respond to antibiotics.
The implant is removed under general anaesthetic. The new implant or a dermis fat graft is placed several months later, once the infection has cleared.
Implant exchange is difficult, especially when the implant has bonded with surrounding tissues. Non-integrated implants are easier to remove. Risks outweigh benefits, and exchange is best avoided unless the existing implant is exposed or infected.
Having no implant does not increase risk of socket infection. However, an implant is desirable to stimulate orbit growth in tandem with the healthy orbit.
Having no implant may cause unsupported orbital fat to shrink and move downward, resulting in shallowing of the gap behind the eyelid. If the child does not have an implant, wearing an artificial eye is important to maintain the gap behind the eyelids as this is likely to shrink if left unsupported.