Who should you expect to show stronger red-eye effect?
blue-eyed people
brown-eyed people
elders
there is no difference
The iris plays no role in the effect, but the blue-eyed people have relatively low melanin in the fundus as well. Therefore, they show a much stronger red-eye effect, as the light passing fundus is not absorbed by melanin. The role of melanin in red-eye effect is nicely demonstrated in case of heterochromia (one eye blue, one brown): typically, only the blue eye displays the effect.
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Answers by country
blue-eyed people
brown-eyed people
elders
there is no difference
answers
Austria
43
Republic of Ireland
14
Ukraine
56
the United Kingdom
124
Greece
21
the Netherlands
14
Australia
34
Poland
10311
the United States
302
Italy
12
Germany
239
Switzerland
33
Belarus
20
Russia
65
the Philippines
21
Canada
30
Nigeria
12
Egypt
13
Unknown
24
India
173