Acrylic conformers effective in congenital anophthalmia

February 1, 2016

Acrylic expanders may be an option for the management of patients with congenital anophthalmos and microphthalmos.

Take-home message: Acrylic expanders may be an option for the management of patients with congenital anophthalmos and microphthalmos.

Reviewed by Thomas E. Johnson, MD

Baltimore-Fitting patients who have congenital anophthalmia or extreme microphthalmia with successively larger acrylic conformers can prepare space for ocular prostheses with minimal complications, according to Thomas E. Johnson, MD.

“This works as well as, if not better than, a lot of the other techniques that have been used or reported,” said Dr. Johnson, professor of clinical ophthalmology, Bascom Palmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore.

Anophthalmia is extremely rare, affecting only 0.18 to 0.4 in 10,000 births. Microphthalmia is only slightly more common, affecting about 1.5 in 10,000.

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Causes include genetic disorders; gestational infections, such as toxoplasmosis, rubella and some strains of influenza; gestational exposure to thalidomide or x-rays; or gestational vitamin A deficiency, Dr. Johnson said. In the absence of a normal eye, sockets will not expand properly leading to a disfigured appearance.

Treatment “is mainly cosmetic,” he said. “It helps patients with their esteem to be able to wear an artificial eye and look normal.”

Ophthalmologists have used a variety of techniques to avoid this problem. One approach is a surgically implanted hydrogel ball implant that expands by osmosis of fluid in the socket, reaching about 10 times their original volume in 2 to 6 weeks. Hydrogel balls are surgically replaced with successively larger sizes.

Complications

 

Such devices have been available for about 20 years, but do not always provide the desired results, Dr. Johnson said.

“There have been reported complications including migration,” he said.

Another approach is a saline tissue expander implanted into the deep socket using titanium T-plate fixation at the lateral orbital rim. This approach requires surgery and multiple computed tomography (CT) scans. Inserting the device sometimes disrupts the important lateral canthus.

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Dermis fat grafting can also expand the orbit. Typically the graft is placed around age 4 to 5 years. Drawbacks include unpredictable growth, atrophy, and poor socket elasticity that prevent the socket from responding well to future prosthetic enlargement.

Other ophthalmologists have attacked the problem using surgery, including canthotomy and osteotomies, but this also can leave scars and may expose the patient to radiation from CT scans increasing the risk of leukemia and brain cancer.

In addition, some research suggests that repeated use of general anesthesia can impair a child’s cognitive development.

Using acrylic expanders

 

Using acrylic expanders

By contrast, Dr. Johnson descried a series of 8 patients in whom he and his colleagues treated 14 sockets with acrylic expanders. These patients did not need surgery until they reached a mean age of 5.73 years when an adult-sized orbital implant was placed.

Of these patients, two required further surgery, in both cases to graft mucous membrane. In one case, the surgery was needed because of a car accident.

“In the other, we may have been too aggressive” in expanding the socket rapidly, he said.

The risk of adverse events from the conformers is small, he said. Acrylic is very inert and very few people develop allergies to it.

Dr. Johnson first became aware of the possibility of using acrylic conformers in 1997 when he read an article by Merritt and Trawnick in the Journal of Ophthalmic Prosthetics describing a similar approach.

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While living in Saudi Arabia, Dr. Johnson collaborated with an ocularist, Yasser Bataineh, who was skilled in creating such acrylic conformers for these patients. Bataineh moved to Florida, and when Dr. Johnson took a position there at Bascom Palmer, the two resumed their collaboration.

In their series of patients, they placed an average of about 20 successively larger conformers in each socket before implanting an orbital implant.

“Usually the conformers are changed very quickly when the child is very young, then you continue gradually expanding them,” Dr. Johnson said. “The ocularist decides how fast to proceed with enlarging the conformers.”

The conformers start out flat and become progressively more rounded. Convexities on their posterior aspect stimulate an indentation in the socket called the pit.

“We think this pit plays a role in causing the socket expansion,” Dr. Johnson said. “In some of these other techniques the pit may not be respected, and that’s why we think the expansion may not be as good.”

Biggest challenges

 

One of the biggest challenges in the procedure is expanding the eyelids, Dr. Johnson said.

“One needs to expand the eyelids to hold the ocular prosthesis, and you also need to expand the boney orbit, because if you don’t, the patient will end up with a constricted socket with the inability to wear a prosthesis,” he said.

This approach works best with motivated parents because both the physician and the ocularist must see the patient frequently, he said.

“If they lose their conformer they have to come in fairly quickly,” he said. “You need to have very dedicated parents.”

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Bilateral cases are easier to treat than unilateral ones because it can be difficult to exactly match the size of a natural eye with a prosthesis.

“Symmetry is very important in facial appearance,” he added.

The treatment requires a team approach. A geneticist and pediatrician should see the patient at the outset to determine whether other systemic abnormalities may result in comorbidities that must be managed.

“Then it’s a very close collaboration between the ophthalmologist and the ocularist,” said Dr. Johnson. “You have to work with an excellent ocularist who is very patient with children.”

Bataineh can fit the conformers without sedation or anesthesia.

“Some people are very talented with that,” Dr. Johnson said. “It takes a special kind of person to be able to do it.”

 

Thomas E. Johnson, MD

E: tjohnson@med.miami.edu

This article was adapted from Dr. Johnson’s delivery of the Ruedemann Lecture at the 2015 meeting of the American Academy of Ophthalmology. Dr. Johnson has no financial disclosures.