The investigators believe that this simple, clear, and objective study may be a great help in understanding the accommodative response during various accommodative stimulation conditions.

The purpose in this study was to investigate physiological changes in accommodative power, pupil diameter, astigmatic value, and axis when visual stimuli were applied under binocular, monocular (dominant eye, non-dominant eye, ipsilateral, and contralateral), and pinhole conditions using the WAM-5500 binocular autorefractor/keratometer (Grand Seiko Co. Ltd., Hiroshima, Japan).

Inclusion Criteria:

1. age between 20 and 40 years
2. spherical equivalent (SE) within ± 4.0 diopters (D)
3. correctable distant and near visual acuity by glasses to 20/20
4. normal ocular alignment.

Exclusion Criteria:

1. disturbance of accommodation (e.g., Adie's pupil, Parkinson's disease, accommodative esotropia, accommodative spasm, presbyopia)
2. disorders that can affect accommodation (e.g., history of ocular trauma, previous ocular surgery)
3. disorders that might limit testing accuracy (e.g., corneal pathological features, cataract, glaucoma, vitreous opacity, and retinal abnormalities).

Subjects who visited the department of ophthalmology in Chung-Ang university hospital for ocular examination