Abstract
Purpose: :
There are currently a wide range of prescribing practices for hyperopic children including full correction, or partial under-correction of the hyperopia. While blur was originally implicated in the drive to emmetropize in this group suggesting under-correction as the more appropriate treatment, more recent evidence suggests that additional accommodative effort to overcome hyperopia is a causal factor in which case -undercorrection might not be necessary. To further assess the role of accommodation in emmetropization of hyperopia, we compared accommodation responses in infants who were emmetropic at first testing through to 26 weeks; infants who had emmetropized by 26 weeks; or infants who had not yet emmetropized by 26 weeks and compared them with older children who had failed visual acuity screening due to clinically significant hyperopia. We investigated whether response to blur resulting from hyperopia differed in the non-clinical versus clinical groups.
Methods: :
A PlusoptiXSO4 photorefractor was used to collect binocular accommodation data from participants viewing a detailed picture target moving between 33cm and 2m. Data from 38 typically developing infants between 6-26 weeks of age were compared with cross-sectional data from children of 5-9 years of age with clinically significant hyperopia (15); correctedy fully accommodative strabismus (14); and 27 age matched controls.
Results: :
Hyperopes, whether corrected or not, and of all ages, underaccommodated at all distances when compared to controls (all p < 0.00001). Lag of accommodation was found to correlate with manifest refraction. Emmetropizing infants accommodated better for near than distance resulting in steeper accommodative slopes. In comparison, the hyperopic patient groups accommodated better for distance than near.
Conclusions: :
Steep accommodation response slopes are typical of emmetropizing hyperopia in infants who accommodate at near to partially overcome hyperopic blur. Clinically hyperopic children with reduced visual acuity do not accommodate to overcome residual hyperopia and thus would be unlikley to accommodated to overcome hyperopia left by an under-correction. This suggests that under-correcting hyperopia with low acuity at referral might not be an appropriate treatment.
Keywords: hyperopia • accommodation