Aim: To investigate trends in the incidence of blindness and the association with laser photocoagulation in patients with type 1 diabetes in Japan.
Methods: Patients diagnosed between 1965 and 1979 under 18 years old. The status of blindness and laser photocoagulation were identified as of January 1, 1995. To examine the time trend, we divided the cohort into two groups; 285 patients diagnosed between 1965 and 1969 (65-69 cohort) and 769 patients diagnosed between 1975 and 1979 (75-79 cohort). Survival analysis was performed using the Kaplan-Meier method. Cox proportional hazard models were used to assess the demographic characteristics.
Results: Blindness developed in 60 subjects in 65-69 cohort and 15 subjects in 75-79 cohort. The incidence of blindness in 75-79 cohort was significantly lower than that in 65-69 cohort (p < 0.0001). The hazard ratio for the blindness in those who received laser photocoagulation in 75-79 cohort significantly decreased to 0.55 (p < 0.01), compared to those in 65-69 cohort when adjusted for the age of onset, gender, and time of diagnosis.
Conclusion: The incidence of blindness significantly decreased for the subjects diagnosed more lately. Laser photocoagulation might have contributed to the decreased blindness observed over time.