Simplify the following text for a Grade 9 native English-speaking person.
Original: Chlamydia conjunctivitis or trachoma was once the most important cause of blindness worldwide , but its role diminished from 15 % of blindness cases by trachoma in 1995 to 3.6 % in 2002 .
Simplified: Chlamydia conjunctivitis or trachoma is a common cause of blindness worldwide . The World Health Organization estimates that it accounted for 15 % of blindness cases in 1995 , but only 3.6 % in 2002 .