Changes in Corneal Topography and Clinical Refraction Following Horizontal Rectus Muscle Surgery

Objectives@#Refractive changes have been studied after muscle surgery in literature but most results are inconsistent. It has been postulated that changes in corneal tension after muscle surgery may cause a change in corneal curvature resulting in the change in refraction postoperatively. This study investigated changes in corneal topography and clinical refraction after horizontal rectus muscle surgery.@*Methods@#Twenty-one eyes of 13 patients underwent horizontal rectus muscle surgery via limbal approach. Manifest refraction, cycloplegic refraction, and corneal topography were measured preoperatively, and postoperatively at day 1 and weeks 1, 2, 4 and 8. The proportion of subjects with at least 0.5 D change from preoperative measurements and the proportion of subjects that needed new prescription postoperative were also computed. Analysis of the results were done using the Friedman test to identify significant differences among measurements at different time periods with post-hoc analysis utilized to identify specific time periods with significant changes from preoperative measurements.@*Results@#Mean corneal keratometry, horizontal, vertical, and oblique astigmatism, obtained topographically showed no significant difference from preoperative measurements. The statistically significant difference in corneal astigmatism in the recession group at day 1, week 4 and week 8 postoperatively was not confirmed when converted to power vectors in both vertical/horizontal (J0) and oblique (J45) astigmatism. Clinical refraction showed a transient myopic shift in spherical equivalent, statistically significant only on postoperative day 1 in the recession group. There was no statistically significant difference in clinical astigmatism. There was ≥ 0.5 D change in spherical equivalent in 60% in both study groups by the end of follow-up. The shift in J0 was more than 10% in the recession group. More than fifty percent (52.4%) needed new prescription for glasses.@*Conclusion@#No statistically significant change in corneal topography and clinical refraction following horizontal rectus muscle surgery were found. Patients should still be refracted at least 2 weeks postoperatively to check if there is a need for change in prescription glasses to improve alignment and/or improve vision.

Astigmatic Changes after Horizontal Rectus Muscle Surgery in Intermittent Exotropia

PURPOSE: To evaluate the changes of refractive astigmatism after horizontal rectus muscle surgery in intermittent exotropic children. METHODS: Sixty-nine exotropic patients were retrospectively reviewed. Of those, 35 patients received unilateral lateral rectus recession (BLR group, 35 eyes) and 34 patients received unilateral lateral rectus recession and medial rectus resection (R&R group, 34 eyes). Non-cycloplegic refractions were measured until 6 months postoperatively. Spherical equivalent (SE), J0 and J45 using power vectors were calculated to determine and compare the changes of refractive astigmatism and axis in both groups. RESULTS: SE significantly decreased after surgery for the first week and did not changed thereafter in both groups (p = 0.000 and p = 0.018, respectively). In BLR group, J0 showed significant changes at the first week and 1 month after surgery (p = 0.005 and p = 0.016, respectively), but in R&R group, J0 changed significantly between 1 week and 3 months postoperatively (p = 0.023 and p = 0.016, respectively). J45 did not change significantly as time passed in both groups (all p > 0.05). There was no statistically significant difference in the magnitude of changes in SE, J0 and J45 between the two groups after the 6-month follow-up (p = 0.500, p = 0.244 and p = 0.202, respectively). CONCLUSIONS: Horizontal rectus muscle surgery in intermittent exotropic children tends to induce a statistically significant change in astigmatism in the with-the-rule direction and myopic shift in SE. This astigmatism change seems to occur within the first 3 months after surgery. Thus, astigmatism induced by surgery should be checked and corrected at least 3 months after horizontal strabismus surgery.

Strabismus Surgery on Congenital Oculomotor Nerve Palsied Eye

In congenital third nerve palsy, the function in four of the six extraocular muscles is compromised, and its treatment is the most difficult problem in paralytic strabismus. In general, either large recession and resection on horizontal rectus muscles or superior oblique muscle transposition is used for treatment. We compared the results of the two methods of surgical therapy. A Total of nine eyes in nine cases underwent surgical correction for ocular alignment in the primary position, In four eyes of four cases horizontal rectus muscle surgery was performed. In five eyes of five cases superior oblique muscle transposition was performed. Postoperatively, one of four cases who underwent horizontal rectus muscle surgery and four of five cases who underwent superior obique muscle transposition resulted in acceptable ocular alignment, in which the angle of deviation at the primary position was within 2 delta. Therefore, in the treatment of congenital third nerve palsy, superior oblique muscle transposition is more effective than horizontal rectus muscle surgery for the correction of ocular alignment.