Lactic Acid Bacteria for Reducing Blue Light-Induced Eye Fatigue

The Application of Lactic Acid Bacteria on Reducing Blue Light-Induced Eye Fatigue in Middle-Aged Adults

With the widespread use of digital devices and prolonged screen exposure, digital eye strain (DES), also known as computer vision syndrome, has become a global public health concern. Emerging evidence suggests that the gut-eye axis may play an important role in ocular health, as gut microbiota imbalance is associated with systemic inflammation and oxidative stress. Specific probiotics may help alleviate eye discomfort through modulation of immune responses and enhancement of antioxidant defense mechanisms. This randomized, double-blind, placebo-controlled study aims to evaluate the efficacy of supplementation with specific probiotics, Bifidobacterium longum BL531 and Lactobacillus reuteri LR1349, in improving digital eye strain symptoms in adults.

Study Overview

• Status: Not yet recruiting
• Conditions: Digital Eye Strain (DES)
• Intervention / Treatment: Dietary supplement: Placebo; Dietary supplement: BL531_low dose; Dietary supplement: BL531_high dose; Dietary supplement: LR1349_low dose; Dietary supplement: LR1349_high dose

• Study Type: Interventional
• Enrollment (Estimated): 150
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Han-Yin Hsu; Phone Number: +886-07-6955680 Ext. 2923; Email: hanin@synbiotech.com.tw
• Study Contact Backup: Name: Chia-Chia Lee; Phone Number: +886-07-6955680 Ext. 2921; Email: cclee@synbiotech.com.tw

Study Locations

• Taiwan
  • Taipei, Taiwan, 106
    • National Taiwan Normal University
    • Contact: Chi-Hao Wu, Professor; Phone Number: +886-02-7749-1427; Email: chwu@ntnu.edu.tw

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Men and women aged 20-65 years
• Daily digital screen use >6 hours for at least 1 year
• Mild to severe digital eye strain (CVS-Q score ≥ 6)
• Mild to moderate dry eye symptoms (OSDI ≥ 13)

Exclusion Criteria:

• Amblyopia or strabismus
• Severe eye diseases (e.g., glaucoma , cataract , retinal disorders, severe corneal disease)
• Ocular surgery within the past 12 months
• Chronic systemic diseases (e.g., uncontrolled diabetes, autoimmune disease, severe liver/kidney impairment, cancer)
• Recent use (<1 months) of steroids, antibiotics, immunosuppressants, probiotics, prebiotics, or eye-health supplements
• Pregnant or breastfeeding
• Allergy to probiotics or study product ingredients
• Eating disorders, psychiatric illness, or cognitive impairment affecting compliance
• Any condition judged unsuitable by the investigator

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

5

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Placebo Comparator: Placebo; Subjects assigned to the placebo group will take one placebo capsule daily within 30 minutes before breakfast throughout the 12-week intervention period.	Dietary supplement: Placebo; Maltodextrin
Experimental: BL531_low dose; Subjects assigned to each intervention group will take one capsule daily within 30 minutes before breakfast throughout the 12-week intervention period.	Dietary supplement: BL531_low dose; 1×10^10 cfu/day
Experimental: BL531_high dose; Subjects assigned to each intervention group will take one capsule daily within 30 minutes before breakfast throughout the 12-week intervention period.	Dietary supplement: BL531_high dose; 2.5×10^10 cfu/day
Experimental: LR1349_low dose; Subjects assigned to each intervention group will take one capsule daily within 30 minutes before breakfast throughout the 12-week intervention period.	Dietary supplement: LR1349_low dose; 1×10^10 cfu/day
Experimental: LR1349_high dose; Subjects assigned to each intervention group will take one capsule daily within 30 minutes before breakfast throughout the 12-week intervention period.	Dietary supplement: LR1349_high dose; 2.5×10^10 cfu/day

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Computer Vision Syndrome Questionnaire (CVS-Q)	The CVS-Q is a questionnaire used to assess digital eye strain associated with prolonged digital screen use. It includes 16 symptoms related to screen exposure. Total scores are classified as 0-5 (none/minimal), 6-12 (mild), 13-18 (moderate), and ≥19 (severe), with scores ≥6 indicating clinically significant digital eye strain.	Baseline, Week 6, Week 12

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Ocular Surface Disease Index (OSDI)	The Ocular Surface Disease Index (OSDI) is a 12-item questionnaire used to assess the severity of dry eye symptoms and their impact on vision-related function and daily activities. Total scores range from 0 to 100, with higher scores indicating greater symptom severity.	Baseline, Week 6, Week 12
Basic vision examination	A comprehensive ophthalmic examination will be performed, including uncorrected distance and near visual acuity, automated refraction, presbyopia assessment, distance and near vision correction, intraocular pressure measurement, and external eye photography for conjunctival hyperemia assessment.	Baseline and Week 12
Pupillary Response Test	Pupillary response testing will be performed using the Oculus Pentacam HR or an equivalent device to evaluate pupil size and response time under light and dark conditions. This assessment provides information on the visual system's adaptation to changes in illumination.	Baseline and Week 12
Tear Secretion Assessment	Tear meniscus height will be measured using the OS1000 Corneal Topographer (SBM sistemi, Italy) or an equivalent device as an indicator of tear secretion.	Baseline and Week 12
Non-Invasive Tear Break-Up Time (NIBUT)	Non-invasive tear break-up time (NIBUT) will be measured using the OS1000 Corneal Topographer (SBM sistemi, Italy) or an equivalent device to evaluate tear film stability. A shorter NIBUT is commonly associated with dry eye symptoms and digital eye strain.	Baseline and Week 12
Corneal Tomography and Topography Analysis	Corneal tomography and topography analysis will be performed using the Oculus Pentacam HR or an equivalent device to evaluate corneal morphology, curvature, thickness, and regularity.	Baseline and Week 12
Accommodative Function Assessment	Accommodative function will be assessed using the ARK-1s Auto Ref-Keratometer (NIDEK, Japan) or an equivalent device to evaluate the eye's focusing ability and quantify accommodative responses associated with ciliary muscle contraction and relaxation.	Baseline and Week 12
Worth Four Dot Test	The Worth Four Dot Test will be used to assess binocular vision and fusion ability by evaluating responses to red and green visual targets, including the presence of suppression or diplopia.	Baseline and Week 12

Collaborators and Investigators

• Sponsor: Synbio Tech Inc.

Study record dates

Study Major Dates

• Study Start (Estimated): September 1, 2026
• Primary Completion (Estimated): August 31, 2027
• Study Completion (Estimated): December 31, 2027

Study Registration Dates

• First Submitted: July 27, 2026
• First Submitted That Met QC Criteria: July 27, 2026
• First Posted (Actual): July 30, 2026

Study Record Updates

• Last Update Posted (Actual): July 30, 2026
• Last Update Submitted That Met QC Criteria: July 27, 2026
• Last Verified: July 1, 2026

More Information

Terms related to this study

• Keywords: Probiotics; Blue Light; Eye Fatigue; Digital Eye Strain
• Additional Relevant MeSH Terms: Eye Diseases; Asthenopia
• Other Study ID Numbers: C202605115

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No