Early detecting and diagnosing primary glaucoma is helpful to reduce blindness and sever visual impairment from primary glaucoma. Opportunistic screening is an effective approach to early find more patients of primary glaucoma. Opportunistic screening means ophthalmologist intentionally find glaucoma patients by the necessary examinations in the individuals who come to hospital due to health physical examination or other diseases. Opportunistic screening should be one part of routine eye examination. Since primary angle closure glaucoma (PACG) and primary open angle glaucoma (POAG) are the different kinds of glaucoma with obvious different clinical features and pathogenesis, the method of opportunistic screening should be also different for them. The concept of continuum of development of PACG and POAG is important for conducting the opportunistic screening for primary glaucoma. The screening test and diagnostic test should be distinguished in the opportunistic screening. The selected screening test should be simple and easily performance. Development of human resource for primary glaucoma is also important for opportunistic screening for primary glaucoma.