AIM:To observe the reason of visual fatigue in Inner Mongolian in order to provide the epidemiological data for the prevention and treatment of asthenopia.

METHODS:This was a retrospective case-controlled study. From January 2011 to December 2014, all the clinical data of 3 502 patients who were diagnosed as asthenopia aged 7～50 was analyzed. The subjects were divided into 4 groups according to the age:(1)7～20 years old: 712 cases;(2)21～30 years old: 603 cases;(3)31～40 years old:694 cases;(4)41～50 years old:1 493 cases. The patients were examed for the conditions of anterior and posterior segment, Schirmer Ⅰ test, break-up time, computer optometry, subjective refraction, horizontal convergence and divergence, distance and near phoria, near point of convergence, accommodative convergence/accommodation ratio, accommodative facility, relative accommodation, amplitude of accommodation and accommodative response. The causes for asthenopia were analyzed by Kruskal-wallis H test first, then comparisons among groups were conducted by Nemenyi test.

RESULTS:The causes for asthenopia were eye-related diseases(49.37%), ametropia(23.36%), accommodation and convergence function problem(21.70%), disorders of extraocular muscles function(5.57%). Kruskal-wallis H test showed significant differences on the prevalence of asthenopia caused by different reasons of the four groups(P<0.05). Nemenyi test showed that the difference was significant on disorders of extraocular muscles function and eye-related diseases among the four groups(P<0.05).

CONCLUSION: The causes of asthenopia are eye-related diseases, ametropia, accommodation and convergence function problem and disorders of extraocular muscles function.