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A. Weiss, R. Sze, J.O. Phillips; Analysis and Treatment of Hypertropia in Plagiocephaly . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2352.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To explore the mechanisms underlying the hypertropia that frequently occurs in coronal synostosis and to refine surgical treatment. Methods: We studied 16 subjects (age at fist visit = 2.3±2.0y) with plagiocephaly of whom 13 had coronal synostosis, 2 had severe deformational plagiocephaly and 1 had cranioscoliosis due to a congenital superior oblique palsy. We measured gaze–dependent binocular alignment and assessed the extraocular muscle paths and rotation axes determined from high–resolution (470 µm/pixel) spiral CT imaging studies in all subjects, and performed quantitative eye movement recordings in 4 subjects. Surgery usually involved weakening of the ipsilateral inferior oblique alone or in combination with the contralateral inferior rectus. We obtained long term follow–up data (6.2±3.8y) on all subjects. Results:We uniformly found an ipsilateral hypertropia (12 diopters, range 3–30 D) in primary gaze in subjects with unilateral coronal synostosis that increased an average of 6 diopters (range = 0–20 D) in contralateral gaze and decreased an average of 8 diopters (range 0–30 D) in ipsilateral gaze. 7 patients had a compensatory head turn. The subjects had CT evidence of lateral translation of the superior rectus or excyclorotation of both vertical recti. Analysis of the off–axis vectors showed angular differences that were too small to explain the hypertropia in primary gaze. Neither severe deformational plagiocephaly nor posterior displacement of the trochlea in a computer model produced a hypertropia in primary gaze, thus providing evidence against the superior oblique underaction theory. Surgery failed to fully correct the hypertropia, which increased over time in some subjects. None of the subjects with unicoronal synostosis obtained better than 800 arcseconds of stereoacuity. Eye movement studies revealed vertical disconjugacy in lateral gaze, consistent fixation with the abducting eye, and a complicated pattern of dysmmetric pursuit and saccadic eye movements. Conclusions: We propose a new mechanism for ipsilateral hypertropia in patients with plagiocephaly that accounts for the findings above, and which may result in better surgical outcomes.
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