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AM Horwood, PM Riddell; The Role of Near Cues in Neonatal Misalignments . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4707.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Neonatal misalignments (NMs) are fleeting, large angle, esodeviations that are seen in most normal infants from birth and resolve by 4 months of age. Observational studies suggest that they occur on attempted near fixation and have found that both frequent or totally absent NMs carry a risk of later refractive error or esodeviation. A remote haploscopic photorefractor (RHP) was used to study the stimuli that precipitate NMs and explore their relationship to accommodation in binocular and monocular conditions. Methods: The RHP was used to measure simultaneous vergence and accommodation responses in infants under six months of age. Occlusion was achieved remote from the infant's face. NMs, the extreme tails of a normal vergence error distribution, were defined as ≷2 S.D. vergence error over target demand (3.14 MA or approx. 11.5°/20D) or ≷2 S.D. more divergent than zero vergence. 3691 binocular and 461 occluded photographs were examined for evidence of NMs, producing 100 (2.7%) binocular, and 50 (10.8%) occluded examples. Accommodation responses occurring during these NMs were measured. Linkages between accommodation and vergence were scored on a four-point scale. Results: Mean age when NMs were found was 7.2 wks. First vergence and accommodation responses occurred at similar mean ages to the age at which most NMs were found. NMs were commonly found immediately after a near (25cm or 33cm) fixation target. Vergence error in MA was always more than accommodation error in D. When occluded, NMs were more common but even less associated with accommodation, (which usually flattened to fixed myopic focus). Links with accommodation were absent or poor in 65% of binocular NMs and 86% of occluded NMs. Better links with accommodation were found in the few NMs that occurred in older infants. NMs were significantly associated with first attempts at prism vergence on the same visit. Conclusion: NMs usually, but not exclusively, occur without associated accommodation. Removal of disparity cues decreases overall accommodation responses but increases the incidence of these large eso errors. If disparity is unavailable and blur does not stimulate accommodation, the only cue to initiate NMs is likely to be proximity/looming. We suggest that these cues are used from soon after birth and may be a major drive to neonatal vergence.
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