Abstract
Purpose: :
To compare accommodative response in with-the-rule (WTR) and against-the-rule (ATR) astigmatism while viewing vertical and horizontal line target at near vision.
Methods: :
Accommodative response was measured at 33cm while subjects viewed through dichroic mirror window in the Grand Seiko WAM-5500 binocular open-field autorefractor. Astigmatic blur was induced in fifteen healthy subjects (ages 19 - 26 years; mean spherical equivalent - 2.54 D; cylinder < - 0.75D) using plus cylinder lens (+0.00 D to +3.00D) for orientation control. Targets were a vertical line and a horizontal line. Each consisted of 40mm long and 1mm wide. Spherical equivalent measurements of approximately - 3.00D would indicate that subjects were accommodating to the 33cm target. For each targets, the mean of spherical equivalent data were calculated.
Results: :
With WTR astigmatism ≥ 1.00D, the mean of the accommodative response obtained with the vertical line target were greater than with the horizontal line target( p < 0.05). With ATR astigmatism ≥ 1.00D, the mean of the accommodative response obtained with the horizontal line target were greater than with vertical the line target( p < 0.05).
Conclusions: :
Posterior focal plane is better focus position than anterior focal plane while viewing a line target parallel to the steeper meridian in eyes. In the eyes with astigmatism, the uncorrected accommodative response varied according to the orientation of visual target.
Keywords: astigmatism • refraction • accommodation