Importance of Accommodation and Eye Dominance for Measuring Objective Refractions

Purpose To explore factors affecting the difference between objective refractive data measured under monocular closed-field viewing and binocular open-field viewing. Design Prospective observational case series. Methods SETTING: Institutional. STUDY POPULATION: Twenty-nine healthy volunteers (58 eyes; mean age, 38.4 ± 10.0 years; range, 25–60 years). OBSERVATION PROCEDURES: Objective monocular refractions (MR) measured with the Nidek Auto Ref/Keratometer ARK-730A; objective binocular refractions (BR) and objective accommodative amplitude (AA) measured with the Grand Seiko Auto Ref/Keratometer WAM-5500; ocular dominance measured using the hole-in-the-card test; presence and magnitude of far/near (30 cm) phoria evaluated by the cover test and alternating cover test using a prism bar. MAIN OUTCOME MEASURE: The difference between objective refractive data measured under monocular closed-field viewing and binocular open-field viewing. Results The spherical equivalent (SE) of the BR was significantly (P <.001) more hyperopic by 0.51 ± 0.33 diopter (D) than the MR. The difference (BR minus MR) tended to decline with increasing age and decreasing AA (r = −0.231, P =.08; r = 0.223, P =.092, respectively). The correlation between age and difference in SE was significant in dominant eyes (r = −0.372, P =.047) but not in nondominant eyes (r = −0.102, P =.60). In nondominant eyes, the amount of near phoria was correlated significantly (r = 0.403, P =.03) with the difference in SE. The correlation was strong (r = 0.598, P = .01) in 17 subjects with more than 3 D of AA. Conclusions Binocular assessment of refraction is important for precise refractive therapy.