Reversal of unilateral medial rectus recession and lateral rectus resection for the correction of consecutive exotropia.

BACKGROUND/AIMS: To evaluate the effectiveness and dose-effect relationship of unilateral medial rectus advancement to the original insertion and lateral rectus recession in the surgical management of consecutive exotropia. PATIENTS/METHODS: The charts of 62 patients operated on for consecutive exotropia in a single-surgeon paediatric ophthalmology practice with a minimum follow-up time of 6 weeks were reviewed. RESULTS: Fifty-two patients were managed with unilateral surgery involving medial rectus advancement and lateral rectus recession. The medial rectus was advanced to the original insertion, and the lateral rectus was recessed by the amount of millimetres it had originally been resected for patients with precise records on previous surgery (within one millimetre of the above). The mean age at surgery for exotropia was 12.86 years. The mean postoperative follow-up time was 2.5 years. The mean preoperative distance exodeviation was 33.4 prism dioptres (PD), and the mean reduction in the angle of strabismus was 33.5 PD. A successful surgical outcome, defined as ocular alignment within 10 PD of orthophoria, was obtained in 41 patients (78.8%) at final follow-up. The mean dose-effect relationship between the reduction in the angle of deviation and the sum of millimetres of the reoperation was 2.9 PD/mm. It varied widely among patients and was strongly correlated with the amount of preoperative exodeviation, that is the patients tended to respond more per millimetre of surgical intervention the greater the preoperative exodeviation. CONCLUSION: The standard reversal of unilateral medial rectus recession and lateral rectus resection is a simple and effective means for correcting secondary exotropia. The dose-effect relationship varied widely among patients and tended to correlate with the amount of preoperative exodeviation.

The role of drug treatment in children with strabismus and amblyopia.

Strabismus, or misalignment of the eyes, is a common ophthalmic problem in childhood, affecting 2 to 5% of the preschool population. Amblyopia is an important cause of visual morbidity frequently associated with strabismus, and both conditions should be treated simultaneously. Pharmacological means for treating strabismus and amblyopia can be divided into 3 categories: paralytic agents (botulinum toxin) used directly on the extraocular muscles to affect eye movements; autonomic agents (atropine, miotics) used topically to manipulate the refractive status of the eye and thereby affect alignment, focus and amblyopia; and centrally acting agents, including levodopa and citicoline, which affect the central visual system abnormalities in amblyopia. Botulinum toxin, the paralytic agent that causes the clinical symptoms of botulism poisoning, can be injected in minute quantities to achieve controlled paralysis of the extraocular muscles. Although the role of botulinum toxin is established in adults with paralytic strabismus, its usefulness in the treatment of comitant childhood strabismus (primary esotropia and exotropia) is not universally accepted. Botulinum injections tend to be more effective with smaller degrees of strabismus, in patients with good binocular fusion, and in managing overcorrections or undercorrections after traditional muscle surgery. Inadvertent ptosis and paralysis of adjacent muscles, unpredictable responses and technical constraints of the injections limit its use in children. Miotic therapy, by altering the refractive state of the treated eye, offers an alternative to optical correction with bifocals in treating esotropia due to excessive accommodative convergence. It is also effective in treating residual esotropia following surgery. The ease of use of glasses restricts the wide application of miotics in these common strabismus syndromes. Atropine, an anticholinergic agent, paralyses the ability of the eye to focus or accommodate. In amblyopia therapy, atropine is used to blur vision in the non-amblyopic eye and offers a useful alternative to traditional occlusion therapy with patching, especially in older children who are not compliant with patching. The neurotransmitter precursor levodopa and the related compound citicoline have been demonstrated to improve vision in amblyopic eyes. The therapeutic role of these centrally acting agents in the clinical management of amblyopia remains unproven.

Magnetic resonance imaging of the arc of contact of extraocular muscles: implications regarding the incidence of slipped muscles.

BACKGROUND: Slipped muscles are complications of strabismus surgery that are encountered more frequently after recessions of the inferior and medial rectus muscles. METHODS: We obtained multipositional high-resolution magnetic resonance imaging of 10 orbits of 6 normal subjects, 9 orbits of 5 patients with thyroid-associated eye disease, and 4 orbits of 2 patients with thyroid-associated eye disease on the day after rectus muscle recessions using a suspension technique. The arc of contact and the distance between the insertion and the point of tangency of each of the extraocular muscles to the globe were measured in primary position as well as in the cardinal fields. RESULTS: The data confirm that the inferior and medial rectus muscles have a significantly smaller wraparound effect on the globe than the superior and lateral rectus muscles, respectively (P =.022 for the vertical rectus muscles; P =.05 for the horizontal rectus muscles, paired t test), and that their insertions may be found several millimeters posterior to their points of tangency in extreme rotation of the globe in their respective field of action. The appearance of the suspended recessed inferior rectus muscle on the first postoperative day and its decreased apposition to the globe raise concerns about the muscle losing contact with the globe in extreme downgaze. CONCLUSIONS: The small wraparound effect of the inferior and medial rectus muscles may explain one of the mechanisms accounting for the increased incidence of slipped muscles encountered after recessions of these muscles.