New insights into visual disturbances accompanying skull deformations

Most children with a craniofacial deformity known as unicoronal synostosis have the eye-alignment abnormality strabismus, reports a study in the May Journal of Craniofacial Surgery, published by Lippincott Williams & Wilkins, a part of Wolters Kluwer Health.

However, contrary to some previous studies, strabismus is no more likely to affect on the same side as the skull deformation compared to the opposite side, conclude Dr. Claire MacIntosh and colleagues of John Radcliffe Hospital, Oxford, U.K.

The researchers reviewed information on 59 children with unicoronal synostosis, focusing on the rates and characteristics of associated visual abnormalities. In infants with unicoronal synostosis, the bones of the developing skull become prematurely fused—one of the joints, or sutures ("soft spots"), joining two skull bones closes before the normal time. The resulting deformity causes a slanted shape of the head. Surgery is needed to restore normal head shape and allow room for the brain to grow.

Another concern for infants with unicoronal synostosis is eye and visual abnormalities, especially strabismus. Sometimes called "lazy eye," strabismus is a condition in which the eyes aren't properly aligned. If the problem isn't treated, vision in the weaker eye will decrease over time—a problem called amblyopia.

In the new study, complete visual assessment detected strabismus in 34 of 59 children with unicoronal synostosis: a rate of 58 percent. However, in contrast to previous research reports, strabismus was no more likely to occur on same side as the prematurely closed suture, compared to the opposite side.

Strabismus was actually more common on the opposite side—56 versus 27 percent—but the difference was not statistically significant. The remaining six patients had "alternating" strabismus.

Other visual problems were common as well—46 percent of the children had a combination of abnormalities called anisometropia and astigmatism. These abnormalities most often affected the eye on the side opposite from the fused suture. In addition, strabismus was found in all patients with certain genetic abnormalities—mutations of the FGF2 or FGF3 gene—as the cause of their unicoronal synostosis.

The results confirm a high rate of strabismus—over 50 percent—and other visual problems among children with unicoronal synostosis. However, the location of the fused suture does not appear to affect which eye is affected by strabismus.

The results have important implications for craniofacial surgeons, plastic surgeons, and other doctors who care for children with unicoronal synostosis. It is vital important to recognize and treat problems like strabismus and anisometropia, which can lead to later vision loss and are not corrected by surgery to repair the skull deformation. Dr. MacIntosh and co-authors stress the need for careful follow-up of children with unicoronal synostosis until good visual acuity and binocular vision are ensured.