Heterophoria in young adults with emmetropia and myopia.

The purpose of this study was to investigate the relationship between heterophoria and refractive error. Thirty-six subjects (11 myopes, 25 emmetropes) participated in this study. Heterophoria was measured with the Free-Space Phoria Card at five different viewing distances (25cm, 33cm, 50cm, 100cm and 300cm). Regardless of the types of heterophoria, the amount of heterophoria reduced towards orthophoric position with increasing viewing distance. Emmetropes and myopes did not show any significant difference in the degree of heterophoria at different viewing distances (F = 0.30, p>0.05) or in the type of heterophoria (χ(2) = 2, p>0.05).