A group of astronomers has warned that some eclipse glasses sold in Japan have been found to be insufficiently lightproof to safely view the upcoming annular solar eclipse and could cause retinopathy when observers see the sun through them.
The Japan committee for the annular solar eclipse 2012, which comprises academic and amateur astronomers, called on observers to make sure they have proper glasses before the eclipse, expected to occur Monday.
The Consumer Affairs Agency said it plans to release a list of improper products after jointly testing products with the National Consumer Affairs Center of Japan.
According to the committee, one of the products studied claimed on the package that its visible light transmission is 20 percent, which means users could suffer from retinopathy when they see the sun through the glasses.
For the first time in 932 years, an annular solar eclipse, often called a ring of fire eclipse, will be visible from large parts of Japan on Monday morning. Observers are advised not to look directly into the sun. They should also turn their back to the sun when they put on or take off eclipse glasses.
The committee said glasses are deficient if observers can clearly see the shape of fluorescent light tubes through them and called on people to check carefully if they have cracks or holes.
During the total solar eclipse of 2009, which was visible in limited areas, 14 people complained of eye problems in Japan, according to University of Tsukuba professor Tetsuro Oshika.
Oshika warns that "tens of thousands of people could suffer from retinopathy" this time, as the eclipse will be observable across the country.