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Satoshi Hasebe, Shin Morisawa, Takashi Furuse, Rie Kobashi; Double-angle Modification of Parks Surgical Table Improves the Outcomes of Unilateral Medial Rectus Recession in Adult Patients with Small-angle Esotropia. Invest. Ophthalmol. Vis. Sci. 2018;59(9):2936.
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The change in deviation per millimeter after unilateral medial rectus recession (MRrec) was reported to be less than that obtained from equivalent amounts of bilateral MRrec (Stack RR, 2003). Besides, adult-onset divergence insufficiency esotropia can be corrected by unilateral MRrec, but its effect was found to be smaller than expected (Ridley-Lane M, 2016). We retrospectively evaluated the surgical dose-effect relationship of unilateral MRrec and determined the usefulness of the modification of the classical surgical table of Parks for different types of small-angle esotropia.
The subjects were 89 successive adult patients with small (7-25 PD) esotropia at distance who underwent unilateral MRrec. The diagnosis includes divergence-insufficiency esotropia, decompensated esophoria, deteriorated microtropia, acute-onset esotropia, and infantile esotropia. The surgical amount was decided by a distance angle of esotropia according to the Parks table before January 2014 (Period 1), and we have increased it, while regarding double the distance angle as surgical target (double-angle modification) to compensate for the tendency of undercorrection found earlier (Period 2). We compared the surgical effects and outcomes at one week after the surgery and the final visit (6-24 months) between the two periods and among the diagnoses.
The linear regression of change in deviation (y in PD) against dose (x in mm) did not differ between the two periods and was clearly below the prediction from the Parks table (y=1.6x+3.1 and y=1.3x+5.5 at distance and near, respectively). The relationships did not differ among the diagnoses. This result cannot be attributed to our surgical technique since the effect of bilateral MRrec agrees well with the predictions. At the final examination, the mean (±SD) undercorrection was 2±6 PD in Period 2 and significantly smaller than that in Period 1 (10±9 PD). No overcorrection was found at distance in either period. An overcorrection less than 10 PD sometimes observed at near in Period 2, but it didn't become problematic clinically.
The double-angle modification of the Parks table clearly improved the surgical outcomes of unilateral MRrec. This seems to be useful not only for divergence-insufficiency esotropia but also for most types of small-angle esotropia.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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