Previous strabismus surgery and eye position under anesthesia

Changes in the interpupillary distance following general anesthesia in children with intermittent exotropia: a predictor of surgical outcomes

PURPOSE

To determine whether changes in ocular alignment following general anesthesia, as measured by interpupillary distance, can be used as a predictor for surgical outcomes in children with intermittent exotropia.

METHODS

The authors obtained digital photographs of 40 children with exotropia and 20 children with epiblepharon (control group) before and immediately after induction of general anesthesia in the primary supine position. Differences in the anatomic interpupillary distance (aIPD) for each patient were measured and compared with the preoperative angles of deviation. They were also correlated with surgical outcomes on the first day and 1 year after surgery.

RESULTS

All 60 patients demonstrated an increase in aIPD following general anesthesia. The mean change in aIPD in patients with exotropia was similar to that in patients with epiblepharon (3.78% ± 2.53% and 3.15% ± 1.05%, respectively). In patients with exotropia, there was a significant positive linear correlation between the preoperative distance deviation (P) and the change in eye position (A): A = 0.362 P - 4.488, r(2) = 0.476 (P < .001). Five (71%) of seven patients whose changes were outside the 80% confidence interval for expected values had poor surgical outcomes on the first postoperative day and four had unsatisfactory results 1 year after surgery.

CONCLUSIONS

Changes in aIPD following general anesthesia were strongly correlated with preoperative angle of deviation. Therefore, they may be a useful predictor of surgical outcomes in children with exotropia.

Postoperative convergence after recovery from general anesthesia in exotropia surgery

PURPOSE

To compare eye position at the end of surgery under general anesthesia with strabismic angles on postoperative day 1 in exotropia surgery.

METHODS

Seventy-eight patients between 3 and 58 years of age who had undergone surgery were divided into two groups (group A = 46 patients with bilateral rectus recession, group B = 32 patients with surgery that included medial rectus resection). Strabismic angles were measured at the end of surgery under general anesthesia using the Hirschberg test and the alternate prism cover test was performed on postoperative day 1.

RESULTS

Mean strabismic angle was 3.15 prism diopters (PD) under general anesthesia and -6.78 PD on postoperative day 1 in group A and -0.31 and -0.37 PD, respectively, in group B. Mean postoperative convergence was 9.93 PD in group A and 0.06 PD in group B, and the differences were statistically significant (P < .001).

CONCLUSION

All patients receiving lateral rectus recession showed approximately 10 PD of convergence. Those who received surgery that included medial rectus resection showed much less convergence and a tendency to be the same as at the end of surgery on postoperative day 1.

Stage I intraoperative adjustment of eye muscle surgery under general anesthesia: consideration of graduated adjustment

The eyes diverge under general anesthesia. The amount of divergence is predictable; there is a linear relationship between the preoperative and the anesthetized eye position. We have confirmed Apt and Isenberg's regression formula for this relationship (A = 0.8 P + 30). We have previously also reported that adjusting the amount of surgery to be done (stage I adjustment) in cases deviating from this correlation by one standard deviation or more (anomalous) significantly improved our surgical success rate to 85%. Since a fixed arbitrary adjustment of 1 mm more or less surgery had improved our surgical success rate significantly, but still left room for higher success rates, we reviewed our anomalous cases to determine whether a graduated adjustment might be expected to produce even higher success rates. A review of cases including additional ones since our last report failed to support this hypothesis. Satisfactory results in these most recent cases have, however, almost doubled the surgical success rate (in anomalous cases) for our stage I fixed arbitrary 1 mm intraoperative adjustment, from 47% to 90%.