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H.J. Simonsz, M.J. C. Eijkemans, Early vs. Late Strabismus Surgery Study Group; Natural Course of Infantile Esotropia: Angle of Strabismus and Refraction in the Early vs. Late Strabismus Surgery Study . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2934.
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Approx. 6000 orthoptic exams in the 532 children entered in the Early vs. Late Strabismus Surgery Study enabled us to describe the natural course of infantile esotropia regarding angle of strabismus and refraction.
In the study, 58 Clinics had recruited 231 children for early (age 6 – 24 months) and 301 for late surgery (age 32 – 60 months). At baseline (11.0 SD 3.7 months) the angle of strabismus, refraction, degree of amblyopia and limitation of abduction had been assessed. Intermediate examinations took place every six months, with measurement of the angle of strabismus, cycloplegic refraction and visual acuity. Children were evaluated at age six in the presence of independent observers. A total of approx. 6000 orthoptic examinations could be evaluated regarding angle of strabismus and refraction. The angle of strabismus data were fitted (Splus) with a random effects model (maximal model with random intercept) with fixed covariates: age, past surgery, angle of strabismus at entry examination, spherical equivalent of the amblyopic eye, and the interaction of these covariates with age, to test the dependence of the course of the angle of strabismus on these covariates.
In the study, children scheduled for early surgery had first been operated at 20 SD 8.4 months, but 8.2% had not been operated at age six, whereas children scheduled for late surgery had been operated at 49.1 SD 12.7 months, but 20.1% had not been operated at age six. In the random effects model, the angle of strabismus decreased by 0.13 degrees per months for children not operated at age six, whereas the angle increased minimally in operated children. The decrease in not–operated children was positively correlated with magnitude of the angle at entry examination and negatively correlated with spherical equivalent. Regression lines were constructed for all children. The intercepts of these varied per child according to terms in the model unrelated to age plus a random factor from a normal distribution with a standard deviation of 2.4 degrees.
From the predictions of the model for the angle of strabismus at age six, based on (1) the angle of strabismus at the age of 11 months, (2) current age, (3) current angle of strabismus and (4) current spherical equivalent, an estimate can be derived for the chance that a spontaneous reduction of esotropia to microstrabismus occurs without surgery, for an individual child.
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