Ocular Effects

Bilberry was reported to have beneficial effects on retinal vascular permeability and tendency to hemorrhage in 31 patients with retinopathy in a German study (10). Benefits were particularly pronounced in patients with diabetic retinopathy, according to the abstract, which was the only part of the study published in English. A study published in Italian (11) showed oph-thalmoscopic improvement in 11 and angiographic improvement in 12 of 14 patients with retinopathy caused by diabetes and/or hypertension, according to a review article (3).

Bilberry jam purportedly improved night vision in Royal Air Force pilots within 24 hours of eating bilberry jam, and at least five European studies showing the beneficial effect of bilberry on night vision were published prior to 1970 (2,3). A 1997 Israeli study published as an abstract (12) found negative results, as did a more recent study performed in 15 Navy Seals. In this trial, Muth and colleagues (2) studied the effect of bilberry extract (25% anthocyanocides) 160 mg taken three times daily for 3 weeks on night visual acuity and night contrast sensitivity in subjects with visual acuity correctable to at least 20/20. An independent laboratory verified the composition of the extract used. Eight subjects were given placebo and seven were given the extract in double-blind fashion. After a 30-day washout, the subjects were crossed over the alternate treatment arm. Nighttime visual acuity and contrast sensitivity were measured under lighting conditions simulating full moonlight (i.e., a luminescence of 0.005 candelas/m2). To measure visual acuity, subjects were presented with Landolt C targets (computer-generated black Cs on a white background) with the opening of the C facing one of eight directions. Each subject was given five tries to correctly identify the direction of the C. If the subject was correct three out of five times, the subject was presented with another five targets of smaller size. Three incorrect responses ended the test. Contrast sensitivity was measured in the same fashion, except that instead of decreasing the size of the targets, the contrast between the target and the background was decreased. Baseline visual acuity and contrast sensitivity were measured three times during the first week of the study; 2436 hours after beginning treatment, 4-6 days after beginning treatment; once between days 12-14; and once between day 19-21. Testing was performed once each week during the 4-week washout. After the second treatment phase, measurements were again taken weekly for 4 weeks. Repeated measures analysis of variance was used to compare the median of the three pretreatment visual acuity and contrast sensitivity measurements to the mean of those obtained during each of the two treatment periods, and to the last measurement taken in each of the two treatment periods. Subjects were also placed into one of four categories depending on whether they showed improvement with both treatments, neither treatment, placebo only, or bilberry only. These results were compared using McNemar's test. No difference between bilberry and placebo was detected. The investigators describe a previous French study (13) in which improvement in five of 14 subjects with poor pretreatment night vision was noted. A larger sample size or use of subjects with poor night vision at baseline may have yielded more promising results.

In a subsequent review (3), the results of two other early studies published in French (14,15) are described. These studies showed that bilberry improved night visual acuity, adaptation to darkness, and recovery of visual acuity after glare. Other articles published during the late 1960s in Italian and German showed beneficial effects of bilberry on retinitis pigmentosa (16) and quinine-induced hemeralopia (17), according to this review. The review also mentions a study published in an Italian journal (18) that purportedly showed that a single dose of bilberry anthocyanosides 200 mg improved elec-troretinographic findings in eight patients with glaucoma, purportedly by stabilizing the collagen of the trabecular network, thus improving aqueous humor outflow.

A review by Head (19) describes a study published in Italian (20) in which bilberry extract (25% anthocyanosides) 180 mg and d,l-tocopheryl acetate 100 mg twice daily for 12 weeks stabilized cataract growth in 96% of 25 treated patients vs 76% of 25 controls (n = 50).

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