This study evaluates the short-term outcomes of surgery involving three or four horizontal rectus muscles in patients with exotropia >40 prism dioptres. The authors evaluate the role of adjustable sutures and identify prognostic factors influencing surgical outcome. They assess the effect of postoperative drift in surgical success. Forty-seven patients were evaluated: 34 requiring three muscle surgery (mean angle 55 ±9.8PD and mean surgery of 22mm) and 13 requiring four muscle surgery (mean angle 72 ±8.8PD and mean surgery of 28mm). All were assessed at one week postoperatively and 12 were overcorrected. Eight eventually aligned, one became under corrected and three remained overcorrected. Higher preoperative angle appeared to predispose to under correction. Adjustable sutures were used in 18 cases: 11 in three muscle surgery and seven in four muscle surgery. There was no significant difference between traditional and adjustable sutures. Not all patients had two month follow-up assessments but of those that did, 77% had a mean drift of 10 ±8.8PD. Rates of successful alignment and overcorrection reduced whilst rates of under correction increased as the drift occurred. The study is limited by small numbers with complete follow-up data and lack of longer-term follow-up.

Three and four muscle horizontal muscle surgery for large angle exotropia.
Chen JH, Morrison DG, Donahue SP.
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Fiona Rowe (Prof)

Institute of Population Health, University of Liverpool, UK.

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