Glaucoma is a leading cause of adult blindness. Primary open angle glaucoma (POAG) is one kind of glaucoma with quite slow development and without apparent symptom. It is difficult to find and diagnose POAG earlier,and so many patients have had serious disability in vision when they go to see a doctor. Recently,the incidence of POAG has increased to a certain degree. Early diagnosis of POAG is critical to postpone or prevent progressive injuries of visual function. On the basis of the recent studies,there is a review about early diagnosis of POAG.