AIM:To evaluate the similarities and differences of conjunctival sac bacteria in the middle age and elder between Tibetan nationality and Yi nationality.

METHODS: This survey study was performed as the standardized training and protocol. A total of 290 eyes of 145 individuals from Tibetan nationality and 272 eyes of 136 individuals in Ganzi Tibetan Autonomous Prefecture received questionnaire survey and ophthalmological examination. The secretion of the inferior palpebral conjunctival sac was embrocated and inoculated on blood plate for 48-72 hours. The bacteria was separated and identified.

RESULTS: All the examinee finished the survey and examination with a good compliance. No significant difference was found in the demography between these two groups of population. The multiple bacterial positive rate in conjunctival sac was 50.7% in Tibetan nationality and that of Yi nationality was 69.9% with a considerably difference between them(P<0.05). The multiple bacterial species were simultaneously detected in 11.6% in Tibetan nationality population and 2.6% Yi nationality, showing evidently difference(P<0.05 ).The positive rate of corynbaccterium in conjunctival sac of Tibetan nationality was statistically lower than that of Yi nationality(P<0.05), but there was no statistical difference in the positive rate of staphylococcus epidemics between two groups(P>0.05).

CONCLUSION: The bacteria positive rate in conjunctiva sac is considerably difference in the population between Tibetan nationality and Yi nationality. The simple bacterial species is found in majority people in two groups of subjects. The positive rate of multiple bacterial strains coexistence is more than the Yi nationality. The bacterial strains is different between Tibetan nationality and Yi nationality.