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Intractable diplopia after strabismus surgery in adults.

OBJECTIVES
To investigate the incidence of persistent intractable diplopia in adults undergoing surgery for long-standing, constant strabismus and to define tests that may be useful for identifying patients at risk for developing this complication.


METHODS
A retrospective medical record review of adults without diplopia undergoing surgery for constant strabismus.


RESULTS
Medical records of 424 adult patients undergoing strabismus surgery were studied. Of these patients, 143 (34%) experienced diplopia when tested preoperatively with prisms to simulate the desired surgical outcome. Only 40 patients (9%) had temporary diplopia after surgery, which resolved in all cases by 6 weeks postoperatively. Three patients (0.8%) developed persistent intractable diplopia. Experiencing diplopia with preoperative prism testing was significantly more likely to result in postoperative diplopia than if diplopia was not present preoperatively (P<.001 and P =.04 for temporary and persistent postoperative diplopia, respectively). Preoperative testing had a sensitivity and negative predictive value for temporary postoperative diplopia of 100%, a specificity of 73%, and a positive predictive value of 28%. Similar values were found for persistent diplopia after surgery with the exception of the positive predictive value, which was only 2%. Patients who did not see double during preoperative testing with prisms never developed diplopia after surgery. However, the presence of preoperative diplopia with prism testing (including a prolonged trial with Fresnel prisms) was infrequently predictive of postoperative diplopia.


CONCLUSIONS
Intractable diplopia after strabismus surgery in adults without previous diplopia is very rare. The diagnostic use of prisms prior to surgery may identify some patients who have little or no risk of postoperative diplopia, as well as a group of patients with a small but definite risk of intractable postoperative diplopia.