Changes in refractive error and axial length after horizontal muscle surgery for strabismus.

PURPOSE: To investigate changes in refractive error following horizontal muscle surgery and to analyze the relationship between these changes and axial length.

METHODS

Patients with intermittent exotropia who underwent bilateral lateral rectus recession (LR group) or unilateral lateral rectus recession with medial rectus resection (RR group) were investigated prospectively. The patients were followed for at least 3 months postoperatively; refractive error, axial length, mean corneal astigmatism, anterior chamber depth, corneal thickness, and intraocular pressure were evaluated at each examination. Postoperative changes in both groups were compared.

RESULTS

A total of 64 eyes of 47 patients were included-34 eyes in the LR group and 30 eyes in the RR group. In both groups refractive error, axial length, and mean corneal astigmatism significantly increased 1 day postoperatively, although the changes in all three parameters returned to their preoperative values within 1 month of surgery and remained stable thereafter for the duration of the follow-up period. There was a negative correlation between changes in axial length and refractive error toward myopia in the 64 eyes on postoperative day 1 (partial correlation coefficient r = -0.637; P < 0.001). Changes in refractive error and axial length were significantly larger in the RR than in the LR group 1 day postoperatively (P < 0.001 and P < 0.001, resp.).

CONCLUSIONS

Horizontal muscle surgery induces a transient myopic shift. This is thought to be due to axial length elongation as well as changes in corneal astigmatism.