Background: Double elevator palsy (DEP) is a not uncommon congenital or acquired clinical entity. Although a full tendon transposition of the horizontal rectus muscles is the widely accepted treatment, the number of reports in the literature is not great, and the techniques used are varied. This study reports on patients with congenital or early onset "acquired" DEP submitted only to a transposition of the horizontal rectus muscles according to Knapp, to add our experience to the literature.
Subjects and methods: Ten consecutive patients without complicating factors had the horizontal rectus muscles transposed to the angle of the insertion of the superior rectus. Patient ages ranged from 10 months to 7 years 4 months. The vertical deviation in primary position ranged for distance from 14 PD to 50 PD (mean 30.6 PD) and at near from 12 PD to 50 PD (mean 27.4 PD). Five patients had only a vertical deviation, and five also a horizontal deviation. The first postsurgical evaluation was done between 7 and 39 days (mean 14.3) and the last between one and 196 months (mean 102.1). The fusional status was assessed using the Worth Four-Dot Test and Major Amblyoscope.
Results: Postoperatively, 3/10 patients had no vertical deviation for distance. Two were undercorrected (by 1 PD, 8 PD); and five were overcorrected (3 PD, 4 PD, 10 PD and two by 25 PD). The mean correction for distance was 36. 4 PD. Three of the ten patients had no vertical deviation at near; two were undercorrected (by 1 PD, 8 PD); and five overcorrected (two by 4 PD, one each by 6 PD, 7 PD, and 9 PD). The mean correction at near was 29.5 PD. Long term followup changes: The correction for distance between the first and last postsurgical evaluation increased (the preop' deviation decreased) in 8/10 patients (range 3 PD to 45 PD, mean 18.6 PD). At near, 9/10 patients had an increase in the correction of the vertical deviation over this period (range 4 PD to 24 PD, mean 13.8 PD).
Conclusion: This transposition procedure can reduce or eliminate the vertical deviation both for distance and at near, and has an increased effect over time.