Dr.SYMA LALWANI, Dr.Jitendra Nenumal Jethani
Abstract
Exotropia surgery is known to have recurrence after corrective surgery. For an angle larger than 45-50 prism diopter (pd), surgery on third or fourth muscle has to be done. We did a study to compare single stage (SS) (3 or 4 muscle) versus two stage (TS) surgery for very large angle exotropia. A total of 16 patients underwent surgery for exotropia (>60 pd). 8 patients had single stage both eye surgery. 8 patients underwent two stage surgery, one eye after another. Mean preoperative angle was 71.1 +/- 6.2 pd for SS group and 73.5 +/- 5.5 pd for TS group. At the end of 2 years, the single stage surgery patients had a recurrence of 15.5 +/- 2.8 pd & two stage surgery patients had an angle of 4.75 +/- 1.8 pd. Using Independent Samples T-test, the difference is significant (p<0.001), the difference in the total surgery done is not significant (p=0.98) suggesting TS surgery is better. We conclude that a very large exotropia should be operated in two stages for stable results in long term.
A very large angle exotropia is characterised by an angle of 60 pd or more. For an angle of 45-50 pd base in usually a 3rd or a 4th horizontal recti of the contralateral eye is to be operated upon. Multiple studies have suggested good results for single stage surgery. However, recurrences are common over a period of time. 1-4 We did a study to compare the single stage surgery versus two stage surgery for very large angle exotropia.
Materials and methods
A total of 16 patients underwent surgery for exotropia (>60 pd). 8 patients had single stage both eye surgery. 8 patients underwent two stage surgery, one eye after another.
Inclusion criteria
- An angle more than 60 pd
- Good vision and alternate exotropia
- Constant angle
- Poor fuse for near and distance
Single stage (SS)
- 3 Muscle or 4 Muscle (two muscles in each eye)
- Depending on the angle
- One of the muscle on adjustable
Two stage (TS)
- One eye two muscle
- Residual deviation
- Other eye surgery depending upon the amount of deviation
The single stage(SS) group the total amount of surgery was calculated by adding the number of recession in mm and resection in mm. The two stage (TS) group the total amount was calculated by adding the first stage numbers and the second stage number. All the single stage patients one muscle was on adjustable. The second stage surgery was done after at least 2 months to 3 months after the first surgery so patient had to wait. In the end we did find that the single stage patients also had to go for the second surgery may be after one year or so the two stage surgery patients at least till 2 years didn’t need any further surgery and were stable.
Results
Mean preoperative angle was 71.1 +/- 6.2 pd for SS group and 73.5 +/- 5.5 pd for TS group. At the end of 2 years, the single stage surgery patients had a recurrence of 15.5 +/- 2.8 pd & two stage surgery patients had an angle of 4.75 +/- 1.8 pd.
Statistical Analysis
Using Independent Samples T-test, the difference is significant (p<0.001), the difference in the total surgery done is not significant (p=0.98) suggesting TS surgery is better.
Discussion
For an Exotropia measuring more than 45-50 prism diopter (pd), surgery on third or fourth muscle (contralateral eye ) has to be done. If we need to operate the other eye should we do this together or should we operate them separately as in two stages.Exotropia surgery is known to have recurrence after corrective surgery. In our own study, (unpublished) (n=80) this was variable with a mean of around 12 +/- 5 pd base in.
For single stage the advantages are
- Correction occurs at one go for patient.
- Finished at one go
- If well aligned Binocular vision may establish
- Stability
In two stage procedure
- Two stage
- Wait between the two surgeries
- More Stable till two years
Three and four horizontal muscle surgeries are effective for correcting large angle exotropia. Higher preoperative deviations were found to be predisposed to undercorrection and therefore more recurrences. Postoperative exotropic drift should be anticipated in cases where large angle exotropia is to be operated upon.1-4Between 1 week and 2 months, 77% of patients experienced exotropic drift averaging 10 ± 9.1 PD. By final follow-up, 90% experienced exotropic drift averaging 15 ± 14.1 PD. Success rates for traditional and adjustable suture surgeries did not differ significantly.Initial postoperative overcorrection of 8 to 14 PD had the highest possibility of gaining successful final motor outcomes.1-4
Although the total amount of surgery was comparable in both groups we found that the two stage surgery was more stable. This could be because
- The Initial drift of one of the eyes is over.
- The final drift of Two stage surgery was much less compared to the single stage surgery
- The second surgery was typically done around 2-3 months after first surgery
- The angle remained stable for a followup of around 2 years after second surgery
Conclusion
We conclude that a very large exotropia should be operated in two stages for stable results in long term
References
- Raiyawa et al. Outcomes of 3 or 4 Horizontal Muscles Surgery in Large-Angle Exotropia. Asia Pac J Ophthalmol (Phila).2015 ;4:208-11.
- Chen J, Morison D, Donahue S. Three and Four Horizontal Muscle Surgery for Large Angle Exotropia. JPOS 2015;52:305-10.
- Li JH, Zhang L. Three muscle surgery for very large angle exotropia. JAAPOS 2013; 17: 578-581
- Yang M et al Single stage surgical outcomes for large angle intermittent exotropia. Plos One 2016; 11: 1-8
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