Laboratory investigationsRelationship Between Motor Alignment at Postoperative Day 1 and at Year 1 After Symmetric and Asymmetric Surgery in Intermittent Exotropia
Introduction
Of the various specific factors which contribute to the variability of the surgical results for intermittent exotropia, X(T), an initial postoperative overcorrection is known to be a major contributor.1, 2, 3, 4, 5, 6, 7 An initial postoperative overcorrection is believed to eliminate not only suppression and stimulate fusional vergence but also to reduce postoperative exotropic drift. In cases of basic X(T), the choice between bilateral lateral rectus recession surgery (BLR, symmetric surgery) and unilateral lateral rectus recession-medial rectus resection surgery (R&R, asymmetric surgery) is largely a matter of preference. Moreover, the amount of initial postoperative overcorrection differs between surgeons. In BLR surgery, Raab and Parks7 advised a 10 to 20 prism diopters (PD) of overcorrection, while Scott et al5 advised a 4 to 14 PD of overcorrection. McNeer8 recommended a 0 to 10 PD of overcorrection.
In R&R surgery, Parks9 advised a few prism diopters of immediate postoperative overcorrection. Souza-Dias and Uesugui2 recommended a 5 to 10 PD overcorrection; however, they cautioned that overcorrections and undercorrections sometimes are the result of greater or lesser amounts of initial overcorrection.
Therefore, the purpose of this study was to determine the relationship between the alignment of the eyes at postoperative day 1 and at year 1. In addition, we attempted to predict the success, undercorrection, and overcorrection rates at postoperative year 1 by examining the alignment at postoperative day 1 following BLR and R&R surgery.
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Materials and Methods
This study includes 103 intermittent exotropes comprising 93 with the basic type and 10 with the pseudo-divergence excess type. Between January of 1993 and March of 1998, 46 patients underwent BLR surgery and 57 patients underwent R&R surgery at the Keimyung University Hospital. Of these patients, 45 were boys and 58 were girls. Their ages ranged from 3 to 17 years with a mean age of 7.1 years.
All patients met the following criteria: basic or pseudo-divergence excess type of X(T), a range of
Results
Preoperatively, the mean alignment and age of the patients who underwent BLR was 27.2 PD and 7.3 years old, respectively, and those who underwent R&R was 28.4 PD and 6.9 years old, respectively. There were no significant differences between the mean alignment or the age of the patients who underwent the two surgical procedures.
Discussion
Almost all patients with X(T) require surgical correction at some time. The surgical results are more satisfactory if the operation is done while the patient still exercises fusion during some portion of the day. Moreover, many known variable factors, such as surgical method, age at onset, age at surgery, preoperative distance and near deviation, preoperative difference in the near and distance deviation angle, duration of the exodeviation, presence of amblyopia, anisometropia, and associated
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