Outcome of 5 mm resection of one medial rectus extraocular muscle for recurrent exotropia.

PURPOSE

To evaluate the success rate of 5 mm resection of one medial rectus (MR) as the second surgery for intermittent exotropia of childhood after bilateral lateral rectus recessions and after unilateral lateral rectus recessions, and to propose a theory of how this surgery works.

CASES

The author performed a retrospective chart review of 10 years experience of routinely performing a 5 mm resection of one medial rectus as the second surgery for exotropia recurrent after unilateral or bilateral lateral rectus (LR) recession. A total of 45 cases of children receiving a second surgery for recurrent exotropia, a 5 mm resection of one medial rectus in all cases, were identified. Ten of the second surgeries were performed with the first surgery having been a large unilateral LR recession. Thirty-five had received bilateral LR recessions as the first procedure. Only those cases needing a third surgery prior to 2 years or with at least two years followup with continued good binocular alignment were included.

OUTCOME

Residual deviations of 8 XT to 10 ET, inclusive, (or less) were considered surgical "successes".

RESULTS

Of the 10 whose first surgery had been a unilateral LR recession (8-9 mm for 9 of the 10), the two year failure rate was 4/10. Of the 35 whose first surgery had been a bilateral LR recession (4.5 to 8.2 mm), the two year failure rate was 4/35. The time to failure after resection of one MR averaged 27 months for the 6/10 failures of the unilateral LR recession group; the time to failure after resection of one MR for the 14/35 failures of the bilateral LR recession group averaged 42 months.

CONCLUSIONS

The more rapid failure of resection of one MR for those whose first surgery was a unilateral instead of a bilateral LR recession suggests that recession of the other LR may yield a higher success rate for the unilateral LR recession group in the future. Resection may work for a long time due to removal of embryonic myosin responsible for restoration of normal linear sarcomeric density.