Background: Glaucoma is group of diseases defined as optic nerve structure damage and functional deficit, being the second cause of irreversible blindness and a leading cause of blindness in patient of 60 ages. 8 % of blindness in 39 million people is due to glaucoma and in Africa it count for 15 %. This disease affects the African race than the Caucasians. This study aimed to assess the effectiveness of early diagnosis and treatment of glaucoma in prevention of glaucoma related blindness among adult patient who attend KCMC ophthalmology department from the year 2012 to 2015. Methodology: A retrospective hospital based cross-sectional study was done. Data were extracted from 80 patient’s files through a random sampling technique and analysed by SPSS version 20, data was checked for completeness and double entered into computer and analysed by using SPSS version 20, Cross tab and binomial logistic regression was carried out where by odd ratio (OR) with its 95% CI was used to measure the association between dependent and independent variables. P value of <0.05 and 95% confidence interval was used to estimate statistical significance of the association. Results: Total of 80 patient’s file were enrolled, median age of participant is 68 years IQR 21.8 years, male being the dominant (30,62.5%) and majority are from Kilimanjaro region (55,68%), (42, 52.5%) visit hospital regularly. Patients who were diagnosed early had few risk of becoming blind. Conclusion: Prevention of glaucoma related blindness has strong association with diagnosis timing, those who were diagnosed late are at higher risk of become blind, as majority come while they are blind and few who are not had poor improvement of Intraocular pressure, and turn easily to blind. KCMC ophthalmology department should extend service to cover her catchment area as majority of her service cover Kilimanjaro region. Primary health care personally should be empowered in term of knowledge and equipment so as they can early diagnose and manage patient, final public awareness of importance of good health seeking behavior and adhere to treatment is very important.