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Oculoplastics: Magnets aid motility in anophthalmic reconstruction
The fourth report from the OSN Section Editor Summit focuses on modern developments in magnets and prosthetic implants.
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A note from the editors:Ocular Surgery News convened its annual Section Editor Summit in February. In this fourth installment of reports from the summit, Oculoplastic and Reconstructive Surgery Section Editor Mark R. Levine, MD, FACS, discusses modern developments in magnets and prosthetic implants.
One of the concepts that I have found to be an interesting innovation, and which actually traces its roots back to the 1940s and 1950s, is the use of magnets for enhancing ocular motility.
Going back even further into the history of the anophthalmic socket, in 1885, P.H. Mules placed a glass spherical implant into an eviscerated socket. That was the beginning of what was then anophthalmic reconstruction.
The sphere replaced lost volume and diminished socket contracture. In 1989, Arthur Perry introduced the hydroxyapatite orbital implant, made from sea coral and designed to be an integrated implant.
Four types of implants
Mark R. Levine |
Now there are four types of implants. There is the simple buried muscle cone implant that most of us in ophthalmology use, the quasi-integrated implant, the exposed integrated implant and the buried integrated implant, with or without a peg.
The simple buried sphere within the muscle cone is actually implanted posteriorly through the rent in Tenon’s capsule, which surrounds the optic nerve, where the sphere is placed in the muscle cone. Then you close posterior Tenon’s, overlap and sew the muscles together and close Tenon’s and conjunctiva.
Next, there is the quasi-integrated implant, which entails the muscles crossing in between the mounds on the implant and sewn together, with good closure once again of Tenon’s and conjunctiva. With the exposed integrated implant, there was a large risk of the exposed implant part getting infected and extruding over time. This has since been abandoned.
Finally, with the integrated implant that Perry developed out of sea coral, there is also a certain degree of risk of complications. The tissue can break down over the implant as the prosthesis rubs on the conjunctiva and Tenon’s capsule, exposing the implant, be it hydroxyapatite or Medpor.
Wrapping the implant with autogenous fascia lata will minimize the exposure risk, again with good closure of Tenon’s and conjunctiva.
Magnets back in vogue
Most recently, the use of magnets has come back into vogue. Researchers at Johns Hopkins have done a pilot study of 18 patients using the Medpor Attractor Magnetic Coupling System (Porex Surgical) with an attractor screw that is placed in the Medpor implant. Tenon’s and conjunctiva must be meticulously closed. Then a magnet is placed in the prosthesis in order to enhance motility. One to three magnets may be placed in the prosthetic shell to enhance motility.
This system enables us to have a well-integrated implant. We do not have to deal with a peg that can become infected, and you have the interface of the magnet under the conjunctiva and Tenon’s capsule to transmit rapid movement to the magnets in the prosthesis.
The question that remains is whether there will be extrusions, both in the short and long term. Also, what about the cost factor?
In conclusion, although this is a reinvention of an old idea, I think the use of magnets has great utility and can be a major step forward in the area of anophthalmic socket reconstruction.
Next issue
Judy E. Kim, MD, will discuss anti-VEGF and other AMD therapies on the horizon.
For more information:
- Mark R. Levine, MD, FACS, is a clinical professor of ophthalmology in the department of ophthalmology at Case Western Reserve University. He can be reached at University Suburban Health Center, 1611 South Green Road, Suite 306A, South Euclid, OH 44121; 216-291-9770; fax: 216-291-0550; e-mail: mlevine@isgwebnet.com. He has no financial interest in any of the products discussed in this article.