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Vidhyapriya Sreenivasan, Yifei Wu, Sonisha Neupane, Don Lyon, Katie Connolly, Kimberly Nicole Warner, T Candy; Objective measurement of phoria and fusional vergence ranges in young children with uncorrected hyperopia. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4580.
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© ARVO (1962-2015); The Authors (2016-present)
Significant hyperopia (>3D) is a risk factor for refractive esotropia, but only a small proportion of hyperopes develop strabismus while others maintain alignment (Ingram, et al., 1990). How do many of them remain aligned? Uncorrected hyperopia may be associated with esophoria when accommodating accurately to the target, and so adequate divergent fusional ranges would be required for alignment. This study evaluates the relationship between phoria, fusional ranges and accommodation in uncorrected hyperopes.
Young children (1-6 years) with hyperopia (HY, cycloplegic SE ≥+3D), no history of spectacle correction, and absence of strabismus and amblyopia were matched in age with typically developing (TD) children. Purkinje image eye tracking and eccentric photorefraction (MCS PowerRefractor) were used to record eye alignment and refractive state simultaneously while children viewed an animated naturalistic target at 33cm. Phoria was derived from the difference between monocular and binocular eye alignments, and then base-in (BI) and base-out (BO) prisms (2-40pd) were introduced to measure fusional ranges objectively.
Mean SE refractive errors were +3.5D (HY) and +0.9D (TD) (averaged across eyes). Mean objective fusional vergence range was similar (p=0.5) between groups for BI (HY: 21.3pd SD±3.2; TD: 22.4pd SD±2.1) and BO (HY: 26pd SD±5.5; TD: 28.0 pd SD±2.8) with ≤4pd difference between each hyperope and their age matched control. Objective estimates of near phoria ranged from low to moderate exophoria in both HY and TD. Mean accommodative response was also similar (p=0.37) between the groups (Mean HY:-1.65 SD±0.2D; TD: -1.98 SD±0.15D) suggesting that hyperopes were accommodating to the near target.
These data suggest that some uncorrected hyperopes achieve exophoria and are capable of producing a range of fusional vergence around alignment, similar to their age matched controls, when accommodating to an interesting target. While the results need to be confirmed in a larger group of hyperopes, they raise the interesting question of whether fusional ranges and phoria can be predictive of strabismus in children with significant hyperopia.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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