Asthenopia or eye strain describes nonspecific symptoms of an eye when it is tired from intensive work. Vaccinium uliginosum is a flowering plant in the genus Vaccinium. This plant is native to cool temperature regions of the Northern Hemisphere. Considering its antioxidative ingredients, the extract of Vaccinium uliginosum is expected to play a significant role in treating various ocular pathologies. The investigators performed a randomized, case-controlled study in healthy subjects and investigated the protective effect of Vaccinium uliginosum extract (DA-9301) on tablet computer-induced asthenopia.

Inclusion Criteria:

1. Healthy subject aged 20 to 65 years with more than 2 hours of daily use of a smart phone or computer including a tablet and television

Exclusion Criteria:

1. Ocular disease in either eye

   • Ocular surface disease
   • Best corrected visual acuity < 20/30
   • Intraocular pressure > 21 mmHg
   • Optical coherence tomography proven retinal nerve fiber defect
   • Significant cataract (lens opacities classification system III)
   • Significant entropion or ectropion
   • Significant tear drainage problem proved with fluorescein dye dilution test

2. Soft or Hard contact lens use 3 or more days a week

3. History of oral intake of health supplement designed to improve asthenopia within 4 weeks before participating this study

4. Pregnant woman

5. Systemic disease

   • Uncontrolled hypertension (systolic /diastolic blood pressure > 140/90mmHg)
   • Uncontrolled diabetes mellitus (fasting blood glucose level > 180mg/dL)
   • Rheumatoid arthritis
   • Malignant disease
   • Active hepatitis (type B and C)
   • Acute or chronic infectious disease
   • Renal disease