Journal List > J Korean Ophthalmol Soc > v.56(3) > 1010221

Jang and Kyung: Contralateral Inferior Oblique Muscle Overaction after Unilateral Inferior Oblique Weakening Procedures

초록

Purpose:

To investigate the effect of unilateral inferior oblique weakening procedures on contralateral inferior oblique muscle functions and factors that may have an effect on contralateral inferior oblique muscle overaction (IOOA).

Methods:

A retrospective chart review was conducted of medical records of 40 patients who underwent unilateral inferior oblique (IO) muscle weakening procedures from 2007 to 2011 and were observed during a follow-up period of more than 6 months. These patients were composed of primary IOOA (4 patients), secondary IOOA due to superior oblique muscle (SO) palsy (21 patients), secondary IOOA due to inferior rectus muscle palsy (1 patient), and dissociated vertical deviation (DVD) accompanied with IOOA (14 patients). Factors that may have an effect on contralateral IOOA after undergoing the operation were assessed.

Results:

There were 7 patients (17.5%) who had over +2 IOOA after operation. IOOA on contralateral eye was increased from average of +0.00 to average of +0.66 ± 0.14 in 6 months after operation ( p < 0.01). There were no statistically significant differences between preoperative factors and functional changes in contralateral IO muscle.

Conclusions:

There were no statistical factors that may have an effect on contralateral IOOA but the possibility of masked SO palsy before performing unilateral IO weakening procedures should be considered. In patients who have unilateral DVD associated with IOOA or small hypertropia, the contralateral IOOA can be more definite after operation; thus caution should be taken before operation.

References

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Figure 1.
The patient with masked bilateral superior oblique palsy who underwent inferior oblique recession in the left eye shows right inferior oblique overaction.
jkos-56-413f1.tif
Figure 2.
The patient with superior oblique palsy and 6 prism diopters of hypertropia with 25 prism dipoters of exotropia who received inferior oblique recession and lateral rectus recession in right eye shows mild limitation of elevation in the operated eye (circle) and contralateral IOOA (arrow). IOOA = inferior oblique muscle overaction.
jkos-56-413f2.tif
Figure 3.
The patient who underwent inferior oblique recession in the left eye shows limitation of elevation, elevation in abduction and adduction and prominent inferior oblique overaction in the right eye.
jkos-56-413f3.tif
Figure 4.
The patient with unilateral dissociated vertical deviation who received inferior oblique anteriorization in the left eye 5 years ago shows combined dissociated vertical deviation in the right eye and inferior oblique overaction.
jkos-56-413f4.tif
Table 1.
Preoperative characteristics of patients
Characteristics  
No. of patients 40
Sex (M:F) 22:18
Age at surgery (years) 12.60 ± 2.4
Preoperative diagnosis  
  SOP 21
  Primary IOOA 4
  DVD with IOOA 14
  IR palsy 1
Combined strabismus  
  Exotropia 30
  Esotropia 5
  None 5

Values are presented as mean ± SD unless otherwise indicated.

SOP = superior oblique muscle palsy; IOOA = inferior oblique muscle overaction; DVD = dissociated vertical deviation; IR = inferior rectus muscle.

Table 2.
Type of surgery
Type of surgery No. of patients Percentage
IO recession only (8 mm) 7 17.5
IO recession only (10 mm) 9 22.5
IO recession (8 mm) + unilateral LR recession 7 17.5
IO recession (10 mm) + unilateral LR recession 7 17.5
IO recession (8 mm) + unilateral MR recession 1 2.5
IO recession (10 mm) + unilateral MR recession 1 2.5
IO recession (8 mm) + bilateral LR recession 4 10
IO recession (8 mm) + bilateral MR resection 1 2.5
IO recession (8 mm) + unilateral LR recession, MR resection 1 2.5
IO anteriorization only 1 2.5
IO anteriorization + unilateral SR recession
1
2.5
Total 40 100

IO = inferior oblique muscle; LR = lateral rectus muscle; MR = medial rectus muscle; SR = superior rectus muscle.

Table 3.
Change of the amount of inferior oblique overaction
  Preoperative Postoperative (6 months) Amount of change p-value (paired t-test)
Operated eye +1.47 ± 0.11 +0.15 ± 0.06 -1.32 ± 0.10 <0.01
Contralateral eye +0.00 +0.66 ± 0.14 +0.66 ± 0.14 <0.01

Values are presented as mean ± SD.

Table 4.
Factors that may have an effect on contralateral IOOA after unilateral IO weakening surgery
Factors Analysis method p-value
Preoperative diagnosis Chi-square test 0.613
Preoperative amount of IOOA Spearman’s rho 0.436
Existence of combined exotropia Fisher’s exact test 0.623
Existence of head tilt Fisher’s exact test 0.488
Amount of IO recession (8 mm, 10 mm) Fisher’s exact test 0.145

IOOA = inferior oblique muscle overaction; IO = inferior oblique muscle.

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