Studies on the relationship of near heterophoria and refractive error

Abstract

Objective To investigate the relationship of refractive error to the underlying mechanism and the direction of deviation of near heterophoria.Methods A total of 267 consecutive heterophoric patients (145 males and 122 females)were reviewed,with an age range of 3 to 44 years(mean 8.0±0.5 years).Near heterophoria and cycloplegic refraction were measured respectively.Results of 63 cases of emmetropia,60 cases showed near exophoria and 3 cases showed near esophoria,and the difference was statistically significant (P-=0.000.Of 47 eases of near esophoria,3 cases of emmetropia,3 cases of myopia and 41 cases hyperopia were showed respectively.Of 220 cases of hyperopia,60 cases showed emmetropia,64 cases myopia and 96 cases hyperopia.A significant correlation between the direction of deviation of near heterophoria and refractive error was demonstrated(x2 =29.47,P=0.000).As for all cases of hyperopia,41 cases showed near esophoria in which 12 cases of mild hyperopia,18 cases of moderate hyperopia and 11 cases of severe hyperopia were ineluded,and,96 cases showed near exophoria in which 56 cases of mild hyperopia,27 cases of moderate hyperopia and 13 cases of severe hyperopia were included.There was a significant relationship between the direction of deviation of near heterophoria and the degree of hyperopic error(x2= 16.611,P=0.000),more cases of near esophoria were found in moderate hyperopic errors and more eases of near exophoria were found in mild hyperopic errors.Conclusions The direction of deviation of heterophoria was correlated to refractive error,and uncorrected hyperopia maybe a major factor in the etiology of near esophoria.A small degree of near exophoria may be a physiological condition,and near esophoria should be a anomalous condition which may be associated with the onset and the progression of myopia. Key words: Heterophoria; Near heterophoria; Refractive error; Nyopia; Hyperopia