Surgery for esotropia with a high accommodative convergence/accommodation ratio: effects on accommodative vergence and binocularity.

BACKGROUND AND OBJECTIVE: To determine the effectiveness of strabismus surgery as an alternative treatment for high accommodative convergence/accommodation (AC/A) ratio (nonrefractive accommodative) esotropia. PATIENTS AND METHODS: Twenty-three consecutive children with an AC/A ratio of 5:1 or greater and a distance-near disparity of 10 prism diopters (PD) or more were studied in a prospective design. Each patient was treated by recession of both medial rectus muscles for the full amount of esotropia measured at near fixation through the full distance hyperopic correction. The magnitude of eso deviation, the AC/A ratio, and the grade of binocularity were measured before and a minimum of 4 months after strabismus surgery. RESULTS: Surgery reduced the mean preoperative eso deviation at near fixation by a factor of 4 (from a mean of 37 PD to a mean of 9 PD). Surgery eliminated the need for bifocals in 96 percent of the patients. The grade of binocular fusion or stereopsis improved in 70 percent of the patients, remained unchanged in 26 percent, and was degraded in 4 percent. Three (13 percent) of the children became exophoric; none of the children were exotropic. CONCLUSION: These results demonstrate that strabismus surgery is an effective alternative to the long-term use of bifocals in the treatment of high AC/A ratio esotropia. Surgery may be more effective than bifocals in restoring normal stereopsis and binocular fusion.

Prevalence of intracranial lesions in children initially diagnosed with disconjugate nystagmus (spasmus nutans)

A small number of children who develop disconjugate nystagmus, torticollis, and head titubation (spasmus nutans) have been found to have optic chiasm or third ventricle gliomas. However, the prevalence of glioma or other developmental abnormalities in this disorder is unknown because no large series of spasmus nutans cases has previously been reported. A reviewer of the records of 67 consecutive children initially diagnosed with spasmus nutans and followed for an average of 3.3 years at the St Louis Children's Hospital revealed the following: 61% had a history of prematurity, developmental delay, or other systemic abnormality; strabismus, most commonly infantile esotropia, developed in 55%; 43% had neuroimaging studies; and 0% had evidence of a glioma or showed signs of tumor on follow-up examinations. From this consecutive patient series, we estimate the prevalence of tumor in spasmus nutans to be less than 1.4%. Without other evidence of an intracranial mass lesion, neuroimaging of infants initially diagnosed with spasmus nutans may not be immediately warranted.

Lateral incomitance in exotropia: fact or artifact?

The prevalence of significant lateral incomitance in patients with nonparetic exotropia is reported to be 22%. We speculated that measurement artifact may be the cause for some cases of apparent lateral incomitance. We measured the effective power of plastic ophthalmic prisms using a helium-neon laser in the frontal plane position and at 10 degrees, 20 degrees, and 30 degrees of rotation from the frontal plane. The rotated prisms represented the situation in which a neutralizing prism rotates with the head during measurement of lateral gaze positions. For prisms of 35 prism diopters or more, even 10 degrees of rotation produced significant artifactual incomitance. For smaller prisms, 20 degrees or more of rotation was necessary to induce significant lateral incomitance. We prospectively measured 40 consecutive patients with exotropia. Only three patients (9%) had true incomitance greater than 5 delta, and only one had incomitance in both directions of gaze. Significant lateral incomitance could be induced in every patient examined by improperly positioning the neutralizing prism. Because the detection of lateral incomitance causes most strabismus surgeons to reduce the amount of surgery they perform, special care is necessary when measuring deviations in lateral gazes.