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Abstract
Purpose
To investigate the relationship between myopic progression and exodrift after surgery in patients with intermittent exotropia (X[T]).
Methods
Eighty-five patients who underwent bilateral lateral rectus recession for X(T) and had a follow-up of more than 1 year were recruited for the present study. Progression of myopia was determined by measuring the difference in spherical equivalent of both eyes between the initial and final refraction divided by the total follow-up time per patient. Postoperative exodrift was calculated by subtracting the deviation at postoperative 6 weeks from the deviation at the last follow-up, and the deviation at postoperative day 1 from the deviation at postoperative 6 weeks. Linear regression was conducted to determine the relationship between postoperative exodrift and myopic progression. The risk factors for recurrence, defined as exodeviation of 10 prism diopters or more at the final examination, were also analyzed.
Results
Sixty-eight (80.0%) subjects showed myopic progression of -0.50 diopters or more, and 47 (55.3%) had recurrence of exotropia during the mean follow-up period of 37.9 months. Patients with myopic progression showed more exotropic drift after postoperative 6 weeks than the patients without myopic progression (p < 0.01). Immediate postoperative overcorrection, oblique dysfunction, and a short follow-up period were associated with a low recurrence, whereas preoperative angle of exodeviation, sensory status, and age at the time of surgery were not.
Conclusions
In patients who underwent bilateral lateral rectus recession for X(T), a greater myopic progression was related with greater postoperative exodrift. As the development of myopia was observed to be axial in nature, the results from the present study raises the possibility that ocular elongation may reduce the effect of recession.
Figures and Tables
 | Figure 1Correlation between late exodrift (EOMfinal - EOM6weeks) and myopic progression. (A) Late exodrift at far = 5.775 - 1.237 × Myopic progression (p=0.034, linear regression). (B) Late exodrift at near = 5.243 - 2.949 × Myopic progression (p = 0.001, linear regression). PD = prism diopters; D = diopters.
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 | Figure 2Schematic explanation of correlation between myopic progression and postoperative exodrift. As the progression of myopia is axial in nature, these results raise the possibility that ocular elongation may reduce the effect of recession.
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Table 1
Comparison of preoperative clinical characteristics between success group and recurred group
Values are presented as mean ± SD or number.
PD = prism diopters; D = diopters.
*Success group is defined as <10 PD exotropia at last follow-up; †Recurred group is defined as ≥10 PD exotropia at last follow-up; ‡Refractive error represents as spherical equivalent; §Fusion at far and near: suppression at far or near: suppression at far and near: diplopia; ΠChi-square test; #Independent t-test.
Table 2
Comparison of clinical findings at final follow-up between success group and recurred group
Values are presented as mean ± SD.
Exodrift is defined as difference in exodeviation from at final follow-up to at postoperative day 1.
PD = prism diopters; D = diopters.
*Success group is defined as <10 PD exotropia at final follow-up; †Recurred group is defined as ≥10 PD exotropia at final follow-up; ‡Independent t-test.
Table 3
Comparison of exodrift between myopic progression group and non-myopic progression group
Values are presented as mean ± SD.
PD = prism diopters.
*Non-myopic progression group is defined as a case of myopic progression less than -0.50 diopters; †Myopic progression group is defined as a case of myopic progression of -0.50 diopters or more; ‡Independent t-test; §Early exodrift is defined as difference in exodeviation from at postoperative 6 weeks to at postoperative day 1; ΠLate exodrift is defined as difference in exodeviation from at final follow-up to at postoperative 6 weeks; #Total exodrift is defined as difference in exodeviation from at final follow-up to at postoperative day 1.
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