Extraocular Muscle Surgery Improves Vision in Nystagmus Patients

Extraocular muscle surgical procedures improve motor and visual outcomes in patients with infantile nystagmus syndrome (INS), according to a new study.

Researchers at Children's Hospital of Pittsburgh (PA, USA) and the University of Pennsylvania Medical Center (UPMC; Pittsburgh, USA) conducted an interventional case cohort study of 100 patients (63% male) with INS between the ages of 1.5 and 59 years, 68% of whom had strabismus. The patients were examined following one of nine eye-muscle surgery procedures: horizontal head posture, without associated strabismus or vergent stamp (22%); chin down posture, with or without horizontal strabismus (16%); strabismus alone, without an associated head posture (15%); both horizontal head posture and strabismus (10%); chin up posture, with or without strabismus (10%); bilateral horizontal rectus tenotomy reattachment only, with no head posture, strabismus, or vergent stamping (9%); multiplane or head posture, with or without strabismus (7%); vergent stamping alone (6%), without strabismus; and torsional head posture, with or without strabismus (5%). The researchers evaluated visual acuity, postoperative head position, strabismic deviation, and eye movement recordings.

The researchers found group mean results that showed significant improvements overall in binocular acuity, strabismic deviation, head posture, and nystagmus optimal foveation fraction (NOFF) and expanded nystagmus acuity function (eNAFX) measurements. There were no statistically significant differences in average acuity outcomes between the nine surgery types. However, the researchers did find that the chin up posture (with or without strabismus) group, and the bilateral horizontal rectus tenotomy (reattachment only, with no head posture, strabismus, or vergent stamping) patients showed a trend toward greater improvement associated with a lower level of starting acuity. In all, although 23% of the patients showed no change postoperatively, 73% had a 0.1 or greater, 18% had a 0.2 or greater, and 15% had a 0.3 or greater improvement in binocular acuity. A total of 12% of the patients underwent repeat surgery. The study was presented at the American Association for Pediatric Ophthalmology and Strabismus annual meeting, held during April 2010 in Orlando (FL, USA).

"The two lines that people get, especially if it goes to functional acuity, are very important; overall, the group means in acuity showed statistically significant improvements. Some patients improved by five lines, some improved no lines, but this is science's way of saying vision was better,” said lead author and study presenter Richard Hertle, M.D. "If you ask your patients after nystagmus surgery if they're functioning better in the world, you'll often get an answer of yes, and we're just trying to quantitate that.”

INS is characterized by the constant movements of the eyes, usually horizontal, and is not directly caused by any sensory visual problems, but by an unstable eye-movement control system. A common symptom of INS is consistent head turn, indicating the patient can see best at a certain angle. The nystagmus signal from the brain that drives the eyes can also affect the neck muscles, causing head nodding.

Related Links:
Children's Hospital of Pittsburgh
University of Pennsylvania Medical Center