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Completed

NCT Number: NCT01942746

Blueberry Effects on Dark Vision and Glare Recovery

Clinical evidence for effects of plant anthocyanins on vision, and particularly night vision is controversial. Two clinical trials were conducted to investigate whether blueberry juice consumption affected visual dark adaptation, functional night vision, and recovery after photo-bleaching of the retina. One trial (S2) employed a 3 week intervention and washout period, and two doses of blueberries plus a placebo. The other trial (L1) employed a 12 week intervention plus an 8 week washout and tested one blueberry juice dose against a juice placebo.

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Key information

Conditions

Blindness and Low Vision Blindness Eye Diseases Nervous System Diseases Neurologic Manifestations Pathological Conditions, Signs and Symptoms Sensation Disorders Signs and Symptoms Vision Disorders Vision, Low

Age range

35 year–65 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Atlantic Food and Horicultural Research Center

Kentville, Nova Scotia, B4N1J5, Canada

About this study

Vision Tests: 1. Dark adaptometry, 2. scotopic visual acuity, 3. scotopic contrast sensitivity, 4. rod/cone conversion, 5. recovery after retinal photobleaching

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • visual acuity better than 6/7.5 on EDTRS acuity chart at 2.5m
  • visual contrast sensitivity within normal range at 2.5m as tested on Visteck 3000
  • stereo acuity better than 80 seconds of arc on Frisby stereoacuity test
  • no ocular history other than refractive glasses
  • no family history of eye disease

Exclusion criteria

  • family history of retinal degeneration, glaucoma, diabetes, hypertension, cataract, or amblyopia (dimness in vision).
  • evidence in subject (upon examination) of amblyopia (dimness in vision), manifest strabismus (unable to focus both eyes on one spot), or anisotropia (non-uniform responsiveness between both eyes).
  • intraocular pressure above 21mmHG from an average of three measures using Mentor tonopen-XL

Treatment and study plan

Blueberry Juice S2

Dietary Supplement

Blueberry Juice S2 was commercially prepared single strength blueberry juice composed of a 50:50 blend of Rubel (Vaccinium corymbosum L.) and Tifblue (Vaccinium ashei Reade) cultivars. Colorimetric analysis showed that S2 juice contained 6.04 (SD=0.20) mg anthocyanins (C3G) eq/g dry mass.

Other names: Single-strength blueberry juice, commercially prepared

Blueberry Capsules S2

Dietary Supplement

Commercially prepared single strength blueberry juice composed of a 50:50 blend of Rubel (Vaccinium corymbosum L.) and Tifblue (Vaccinium ashei Reade) cultivars was freeze dried then powdered and encapsulated in gelatin capsules. Colorimetric analysis indicated an anthocyanin concentration in the powder of 2.37(SD=0.18) mg C3G eq per capsule.

Other names: freeze-dried blueberry juice powder

Placebo Capsule S2

Dietary Supplement

Placebo Capsule S2 (containing no anthocyanins) were prepared by freeze drying red beets and grinding them to fine powder before encapsulating in gelatine capsules. Red beets do not contain anthocyanins.

Other names: Red beet powder

Placebo Juice L1

Dietary Supplement

Placebo juice was prepared from water, sugars, citric acid, sodium citrate, and artificial colors and flavours, then pasteurized. The placebo juice contains no anthocyanins.

Blueberry Juice L1

Dietary Supplement

Blueberry Juice L1 was commercially prepared single strength blueberry juice composed of a 50:50 blend of Rubel (Vaccinium corymbosum L.) and Tifblue (Vaccinium ashei Reade) cultivars. Colorimetric analysis showed that L1 juice contained 6.83 (SD=0.20) mg cyanidin-3-glucoside equivalents (C3GE)/g dry mass at the start of the study, declining to 5.52 (SD=0.09) mg C3GE/g dry mass after 3 months refrigerated storage.

Other names: single strength blueberry juice, commercially prepared

Primary outcomes

  1. Rate of vision adaptation to low light after blueberry juice and placebo ingestion for 3 weeks (S2).

    Time frame: Pre-intervention, and changes after 3 weeks of intervention, and again after 3 weeks of washout

    Effect of blueberry products and placebo on the rate of vision adaptation to low light. The rate of vision adaptation is measured by lowest perceptible light intensity after 30 min of darkness (dark threshold); time to reach dark threshold (min); time to reach rod/cone transition (min) [Time Frame: Pre-intervention, after 3 weeks intervention, again after a 3 week washout.] [Designated as safety issue: No]

  2. Rate of vision adaptation to low light after ingestion of blueberry juice and placebo for 12 weeks (L1).

    Time frame: Preintervention, and changes after 8 and 12 weeks of intervention and after 4 and 8 weeks of washout

    Effect of blueberry products and placebo on the rate of vision adaptation to low light. The rate of vision adaptation is measured by lowest perceptible light intensity after 30 min of darkness (dark threshold); time to reach dark threshold (min); time to reach rod/cone transition (min) [Time Frame: Pre-intervention, after 8 and 12 weeks intervention, and again after 4 and 8 weeks washout] [Designated as safety issue: No]

Secondary outcomes

  1. Rate of recovery of visual acuity after retinal photostress (S2).

    Time frame: Pre-intervention testing and testing for changes after 3 weeks of intervention and 3 weeks of washout

    After dark adaptation testing (primary outcome) and contrast sensitivity and visual acuity testing (other pre-specified outcome measures), participants are subjected to photostress of the retina using bright light. The time (sec) required to recover pre-stress acuity is measured.

  2. Rate of recovery of visual acquity after retinal photostress (L1).

    Time frame: Pre-intervention and then testing for changes after 8 and 12 weeks of intervention and 4 and 8 weeks of washout.

    After dark adaptation testing (primary outcome) and contrast sensitivity and visual acuity testing (other pre-specified outcome measures) participants are subjected to photostress of the retina using bright light. The time (sec) required to recover pre-stress acuity is measured.

Other outcomes

  1. Visual acuity and contrast sensitivity testing after dark adaptation (S2).

    Time frame: Testing preintervention and testing for changes after 3 weeks of intervention and 3 weeks of washout

    After dark adaptation testing (primary outcome measure) and before measuring rate of recovery from photo stress (secondary outcome) visual acuity in darkness and contrast sensitivity in darkness was measured using defined optotypes with different degrees of crowding and contrast. Performance was defined as the number of correct answers in 12 tests of acuity and 8 tests of contrast sensitivity.

  2. Visual acuity and contrast sensitivity testing after dark adaptation (L1).

    Time frame: Testing preintervention and testing for changes after 8 & 12 weeks of intervention and 4 & 8 weeks of washout

    After dark adaptation testing (primary outcome measure) and before testing rate of recovery from photo stress (secondary outcome) visual acuity in darkness and contrast sensitivity in darkness was measured using defined optotypes with different degrees of crowding and contrast. Performance was defined as the number of correct answers in 12 tests of acuity and 8 tests of contrast sensitivity.

Sponsors and collaborators

Lead sponsor

Atlantic Food and Horticulture Research Center

Other Gov

Collaborators

  • Dalhousie University
  • U.S. Highbush Blueberry Council

Registry information

Official study title

Placebo-controlled Cross-over Studies Examining Blueberries Effects on Dark Vision and Recovery After Photo-bleaching

Important dates

Study start
2005
Primary completion
2006
Study completion
2006
First posted
Sep 16, 2013
Registry last updated
Sep 16, 2013

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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