Blindness and Low Vision
Conditions
Keywords
blueberry, anthocyanin, dark vision, photo bleaching, Visual Perception, Photic Stimulation
Brief summary
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.
Detailed description
Vision Tests: 1. Dark adaptometry, 2. scotopic visual acuity, 3. scotopic contrast sensitivity, 4. rod/cone conversion, 5. recovery after retinal photobleaching
Interventions
DIETARY_SUPPLEMENTBlueberry Juice S2
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.
DIETARY_SUPPLEMENTBlueberry Capsules S2
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.
DIETARY_SUPPLEMENTPlacebo Capsule S2
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.
DIETARY_SUPPLEMENTPlacebo Juice L1
Placebo juice was prepared from water, sugars, citric acid, sodium citrate, and artificial colors and flavours, then pasteurized. The placebo juice contains no anthocyanins.
DIETARY_SUPPLEMENTBlueberry Juice L1
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.
Sponsors
Dalhousie University
U.S. Highbush Blueberry Council
Atlantic Food and Horticulture Research Center
Study design
Allocation
NON_RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
BASIC_SCIENCE
Masking
DOUBLE (Subject, Outcomes Assessor)
Eligibility
Sex/Gender
ALL
Age
35 Years to 65 Years
Healthy volunteers
Yes
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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Rate of vision adaptation to low light after blueberry juice and placebo ingestion for 3 weeks (S2). | 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) \[Time Frame: Pre-intervention, after 3 weeks intervention, again after a 3 week washout.\] \[Designated as safety issue: No\] |
| Rate of vision adaptation to low light after ingestion of blueberry juice and placebo for 12 weeks (L1). | 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
| Measure | Time frame | Description |
|---|---|---|
| Rate of recovery of visual acuity after retinal photostress (S2). | 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. |
| Rate of recovery of visual acquity after retinal photostress (L1). | 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
| Measure | Time frame | Description |
|---|---|---|
| Visual acuity and contrast sensitivity testing after dark adaptation (S2). | 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. |
| Visual acuity and contrast sensitivity testing after dark adaptation (L1). | 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. |
Countries
Canada
Outcome results
None listed