The effects of using virtual reality devices on the eye

Visual parameters measured before and after the use of VR devices or smartphones for 2 hours:
1. Refraction and accommodation measured using a binocular open-field refractor (Auto Ref/Keratometer WAM-5500, Grand Seiko Co. Ltd, Hiroshima, Japan)
2. Monocular near-point accommodation (NPA) obtained using Donder’s push-up method. A 20/30 single letter on a fixation stick positioned approximately 50 cm from the subject served as the target, and it was moved gradually closer to the subject at a rate of approximately 5.0 cm/s until the subject noticed the blurring of the target.
3. The near-point of convergence (NPC): the fixation target, the starting point of the examination, and moving velocity of the fixation target were the same as those previously described for the NPA measurement. The first point at which the corneal reflex of the participants began to extend outward was considered the endpoint.
4. Stereopsis measured using a near stereopsis vision test (Stereo Fly SO-001 test; Stereo Optical Co., Chicago, IL, USA). Stereopsis of 2500–1200 s of arc, 800–40 s of arc, and 400–100 s of arc measured using fly photos, graded circle test, and animal test for children, respectively.
5. The presence and magnitude of ocular deviations at far (5 m) and near (33 cm) distances verified using the cover test and alternating cover test with a prism. A standard set of loose plastic prisms was used for all measurements.

Measured before and after the use of VR devices or smartphones for 2 hours:
1. Choroidal thickness measured using the Heidelberg Eye Explorer software (Heidelberg Engineering, Heidelberg, Germany) (Version 1.9.10.0) provided by the instrument manufacturer. The researchers manually selected a new line at the choroid–scleral border (CSB). They retained the automatically defined Bruch’s membrane (BM) line, and the software calculated the vertical distance between the two segmentation lines. The choroidal thickness was defined as the vertical distance between the BM and CSB.
2. Subjective symptoms measured using a questionnaire based on a computer vision syndrome questionnaire, including dry eye symptoms (burning, feeling of a foreign body, excessive blinking, tearing, dryness, tingling, and increased sensitivity to light), visual disturbance (blurred vision, double vision, and difficulty focusing for near vision), and neurological symptoms (headache, dizziness, and nausea). The symptom sensation questionnaire included six identical analog scales (0 = none to 6 = too severe to tolerate), and the subject recorded the magnitude of each symptoms compared relative to that at the baseline