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Steven D Maxfield, Jae Ho Jung, David A Leske, Jonathan M Holmes; Effect of medial rectus attachment on postoperative drift following surgery for consecutive exotropia. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2455.
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To determine whether post-op drift is associated with the intra-op location and type of attachment of the medial rectus muscle (MR).
We reviewed the records of all patients who underwent unilateral MR advancement (+/- resection) and lateral rectus (LR) recession for consecutive exotropia (XT) over 10 years (n=48) meeting the following criteria: XT ≥10 prism diopters (pd), history of esotropia (ET) surgery, and no prior XT surgery. Patient ages ranged from 9 to 82 years. Median pre-op angle by prism and alternate cover test for distance was 25 pd XT (12-60 pd). Location of the distal end of the MR at the start of consecutive XT surgery was classified in 1 of 4 ways (1) behind the pulley and not attached (n = 4), (2) attached to the pulley but not the sclera (n = 7), (3) abnormally attached to the sclera via a stretched scar or pseudotendon (n = 10), and (4) normally attached to sclera (n = 28). An adjustable suture on the LR was used with an immediate post-op target angle of 2-10 pd ET (achieved mean 8 pd ET, range 2-14 ET). Exotropic drift (exodrift) was calculated at 6 weeks and 1 year post-op.
Overall, mean exodrift at 6 weeks was 4.7±7.2 pd at distance and 0.2±8.5 pd at near (n=42). At 1 year, mean exodrift from adjustment was 5.6±8.8 pd at distance and 0.9±11.5 pd at near (n=22). Based on MR attachment type, the greatest post-op exodrift for distance at 6 weeks occurred when the MR was behind the pulley, followed by when there was an abnormal attachment, then a normal attachment, then attachment to the pulley (14.3±12.4 pd, 5.5±4.7 pd, 5.1±4.7 pd, -1.7+9.6 pd, P=0.8). For near exodrift at 6 weeks, greatest exodrift was when behind the pulley, then normal attachment, abnormal attachment, and at the pulley (6.5±10.2 pd, 1.5±7.1 pd, -1.7±2.4 pd, -4.7±14.2 pd, P=0.4). This same decreasing order (greatest when behind the pulley) was observed at 1 year for both distance (23.0±4.2 pd, 6.7±4.0 pd, 5.2±5.8 pd, -5.5±8.5 pd, P=0.01) and near (13.7±15.9 pd, 3.3±6.7 pd, -1.2±4.6 pd, -12.0±13.4 pd, P=0.07).
Following unilateral LR recession and MR advancement for consecutive XT, post-op exodrift is common, but appears to be greater if the MR is found behind the pulley. Surgical dosing and post-adjustment target angles should account for differences in MR attachment and location.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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