Introduction Glaucoma constitutes a group of disorders with diverse pathogenesis associated with an elevated intraocular pressure in majority of the cases with characteristic pattern of optic neuropathy and loss of visual field. It is one of the leading causes of blindness worldwide. Although the number of people having glaucoma varies in different countries, it is estimated that approximately 66.8 million people are affected worldwide, out of which 6.6 million are blind. 1 Out of them, Primary Open Angle Glaucoma is the most common type of glaucoma, accounting for 90% of all cases. 2 Primary Open-Angle Glaucoma is a multi-factorial optic neuropathy that is chronic and progressive with characteristic acquired loss of optic nerve fibers. Such loss develops in the presence of open anterior chamber angles, characteristic visual field abnormalities and intraocular pressure that are too high for the continued health of the eye. It manifests by cupping and atrophy of the optic disc, in the absence of other known causes of glaucomatous disease. 3 The exact cause of Primary Open-Angle Glaucoma is not known, although many risk factors have been noted. Identifying risk factors is important because this information may lead to the development of strategies for disease screening and prevention and may be useful in identifying persons for whom close medical supervision is indicated. Besides increased Intra ocular pressure, factors known to be associated with an increased risk for the development of glaucoma include advanced age, decreased corneal thickness, racial background, and a positive family history. Data also support Myopia, Diabetes mellitus, 4 and arterial hypertension, 5 Some studies consider that males are 3 Vol. 61, No. 8, August 2011 778 Original Article Frequency of primary open angle glaucoma in Abbasi Shaheed Hospital Uzma Taqi, 1 Uzma Fasih, 2 Syed Farhan Amjed Jafri, 3 Arshad Sheikh 4 Baqai Medical University, 1 Department Ophthalmology, Abbasi Shaheed Hospital, 2,4 Civil Hospital, 3 Karachi. Abstract Objective: To determine the frequency of Primary Open-Angle Glaucoma in different age groups. Early diagnosis of Primary Open Angle Glaucoma can prevent irreversible damage to vision. Methods: This cross sectional study was conducted at the Abbasi Shaheed Hospital, Karachi from 2005 to 2006. A total of 149 glaucoma patients between the age groups of 30 to 70 years were included. Primary Open Angle Glaucoma was diagnosed on the basis of glaucomatous optic nerve damage, abnormal visual fields and optic disc cupping with or without elevated intra ocular pressure with open-angle on gonioscopy SPSSv.8 was used for data entry and descriptive analysis. Results: The total patients in less than 40 years of age group were 2 (1.34%), in 41-50 years age group were 29 (19.46%), in 51-60 years of age group were 47 (31.54%), and in 61-70 years age group were 71 (47.65%). Conclusion: The results show that there is a high frequency of primary open angle glaucoma among people over age of fifty years. Therefore this population in particular, should be monitored carefully for open angle glaucoma, as early diagnosis and therapy may decrease visual morbidity. Keywords: Open angle glaucoma, Frequency, Karachi, Age (JPMA 61:778; 2011).