Introduction: Systemic diseases such as hypertension and diabetes mellitus (DM) have been identified as the risk factor for glaucoma. However, there is minimal knowledge on the impact of systemic diseases on severity of glaucoma. This study aimed to determine the association between systemic disease and systemic treatment and severity of glaucoma. Materials and Methods: A cross-sectional study was conducted involving 298 primary open-angle glaucoma (POAG; 169 high tension glaucoma (HTG) and 129 normal tension glaucoma (NTG)) patients presented at the eye clinic of two tertiary hospitals in Malaysia between March and August 2012. The severity of POAG was based on Hodapp-Parrish-Anderson′(HODAPP) classification on Humphrey visual field 24-2 analysis. Only the right eye was selected when both eyes were eligible. Systemic diseases and treatment were retrieved from medical record or traced from the private practitioner or health clinic. Results: Systemic hypertension was the commonest systemic disease (56.4%) among POAG. There was no significant association between systemic diseases and severity of POAG. More than two systemic diseases were found in43.8% of patients with mild glaucoma. There was also no significant association of systemic treatment such as systemic antihypertensive drugs with severity of glaucoma. Conclusion: Systemic diseases such as systemic hypertension are not associated with severity of POAG. In fact, the presence of systemic disease (sick body) may lead to early detection of glaucoma (sick eye).′Sick body′ may prevent ′sicker eye′.