Abstract
Purpose :
Some binocular open-field autorefractors have been developed to avoid errors resulting from measurement using conventional monocular autorefractors under unnatural conditions. There may be smaller errors in older subjects with less accommodation amplitude (AA) because the instrumental myopia is smaller in older subjects. This study tested the hypothesis that the difference between binocular and monocular objective refractions is less in older subjects with less AA than in younger subjects.
Methods :
Fifty-eight healthy eyes of 29 subjects aged 25 to 60 years (mean, 38.4 ± 10.0 [standard deviation] years) were enrolled prospectively. Objective monocular refractions (MR) were measured with the Nidek Auto Ref/Keratometer ARK-730A (-2.20 ± 2.09 diopters [D]). Objective binocular open-field refractions (BR) (-1.69 ± 2.07 D) and objective AA were measured with the Grand Seiko Auto Ref/Keratometer WAM-5500. Ocular dominance was determined by the hole-in-the-card test. The presence and magnitude of far and near (30 cm) phoria were evaluated using the cover test and alternating cover test using a prism bar.
Results :
The BR was significantly more hyperopic than the MR by 0.51 ± 0.33 D (P < 0.001). The results of subtracting the MR from the BR were significantly negatively correlated with age (r = -0.231, P = 0.04) and positively correlated with AA (r = 0.223, P = 0.046). When dominant eyes (DE) and non-dominant eyes (NDE) were assessed separately, the correlation between the BR minus the MR and age remained significant in the DE (r = -0.372, P = 0.02) but not in the NDE (r = -0.102, P = 0.30). Far and near phoria were present in one and 10 subjects, respectively. The results of the BR minus MR were significantly correlated with the amount of near phoria (r =0.403, P = 0.02) in the NDE, although there was no correlation in the DE (r =0.110, P = 0.29).
Conclusions :
Our results are consistent with our hypothesis that the difference between binocular and monocular objective refractions is less in older subjects with less AA. The ocular dominance and position in addition to the AA should be considered when dealing with data measured by monocular instruments.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.