J Korean Ophthalmol Soc.  2015 Mar;56(3):420-426. 10.3341/jkos.2015.56.3.420.

Dose-Effect Relationship of Unilateral Medial Rectus Resection for Recurrent Exotropia

• Chung YK
• Lee SY
• Lee YC

• KMID: 2339049
• DOI: http://doi.org/10.3341/jkos.2015.56.3.420

Abstract

PURPOSE
To investigate the dose-effect relationship of unilateral medial rectus resection for recurrent exotropia after bilateral lateral rectus recession.
METHODS
This study comprised 39 patients who underwent unilateral medial rectus resection for recurrent exotropia under 25 PD and bilateral rectus recession for prior surgery of exotropia. The medial rectus was resected from 5.0 to 7.0 mm according to angle deviation at a distance. The postoperative deviated angle was checked at one week, 3 months and 6 months postoperatively to investigate the amount of corrected deviation per resected muscle.
RESULTS
The average preoperative deviation was 21.33 +/- 2.96 PD. We resected mean 6.26 +/- 0.57 mm of the medial rectus muscle. The postoperative deviated angle was 0.82 +/- 3.47, 1.87 +/- 3.10 and 5.40 +/- 4.79 PD at 1 week, 3 months and 6 months after surgery, respectively. The corrected deviated angle per millimeter (mm) was 3.29 +/- 0.68, 3.17 +/- 0.58 and 2.75 +/- 0.89 PD at 1 week, 3 months and 6 months after surgery. There were no significant differences among the changes of postoperative deviation per millimeter according to the amount of medial rectus (MR) resection (p-value = 0.423, 0.382) The success rate was 89.75%, 92.31% and 87.18% at 1 week, 3 months and 6 months after surgery, respectively. The expected corrected angle according to the amount of resection remained constant and was 3.04-3.22 PD/mm at 3 months after surgery and 2.79-2.82 PD/mm at 6 months after surgery.
CONCLUSIONS
The dose-effect per millimeter was decreased as time passed. There was no statistical difference among the corrected deviation angles per millimeter according to the amount of MR resection. We expect that the calculated dose-effect relationship may be a useful guideline for unilateral medial rectus resection for recurrent exotropia.

Keyword

Dose-effect; Exotropia; Medial rectus resection; Recurrent exotropia; Unilateral medial rectus resection

MeSH Terms

Exotropia*
Humans

Figure

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  Figure 1. Correlation between preoperative distance deviation and medial rectus resection. R2 = correlation coefficient; PD = prism diopter.

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  Figure 2. Postoperative exodrift after secondary operation as time passed. PD = prism diopter; POD = postoperation day.

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  Figure 3. The graph of change of postoperative deviation per a millimeter according to the length of medial rectus muscle resection. PD = prism diopter; MR = medial rectus.

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  Figure 4. The graph of expected change in deviation on the basis of unilateral medial rectus resection and the regression equation. R2 = correlation coefficient.

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  Figure 5. Expected change in deviation on one millimeter in unilateral medial rectus resection (A: 3 months; B: 6 months). PD = prism diopter.

Reference

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