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The authors conducted this study to evaluate the shift in rectus muscle insertion when the muscle is disinserted from the globe but before it is recessed and / or transposed. They measured the amount of central rectus muscle insertion shift after disinsertion and identified factors that may have an effect on the insertion shift. The study included 110 patients (51.8% female). Mean age was 32.2 ±27.8 years. Childhood onset strabismus was present in 56.4%, 10.9% were paralytic and 8.2% were restrictive strabismus. Prior surgery was noted in 19.1%. Surgery was to the medial rectus (48.2%), lateral rectus (41.8%), inferior rectus (9.1%) and superior rectus (0.9%). Before disinsertion, the mean limbus-insertion distance was 5.0 ±1.1mm for the medial rectus and 6.3 ±0.8mm for the lateral rectus. After disinsertion, these measurements reduced to 4.6 ±0.9mm and 5.4 ±0.7mm respectively. Two significant factors correlated with insertion shift. The first was forced duction test and the second was limbal insertion distance before disinsertion. Moderate / severe forced duction test had the greatest effect on shift. Shift was not affected by age, sex or other preoperative factors. The authors discussed that the amount of shift of the muscle insertion after disinsertion may potentially affect the dose response of strabismus surgery when the measurement is made from the insertion. Therefore, with forced duction test restrictions and longer limbal insertion distance, surgeons could consider measuring from the limbus rather than the insertion.

Extraocular muscle insertion shift after disinsertion during strabismus surgery.
Honglertnapakul W, Capo H, Cavuoto KM, McKeown CA.
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Fiona Rowe (Prof)

Institute of Population Health, University of Liverpool, UK.

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