[The methodology and focus in blindness prevention from an epidemiologic point of view].

The present main causes of blindness in China are senile cataract, primary glaucoma' trachoma and corneal infections, and 80% of the blind are over 50 years of age, 75% become blind before 10 or after 50 years of age, and among 40% of the blind, the interval between visual loss in both eyes was over 1 year. The authors are of the opinion that the focus of efforts for blindness prevention should be directed to patients over 50 years of age, and particularly those of unilateral blindness, so as to prevent them from becoming bilaterally blind.