2020–2021 BCSC Basic and Clinical Science Course™
Chapter 7: Primary Open-Angle Glaucoma
Primary Open-Angle Glaucoma
Association with Systemic Conditions
The evidence related to diabetes mellitus as a risk factor for glaucoma is difficult to interpret. The Beaver Dam Eye Study, the Blue Mountains Eye Study, and the Los Angeles Latino Eye Study found an increased risk of OAG in participants with diabetes. However, the Framingham Study, the Baltimore Eye Survey, the Barbados Eye Study, and a revised analysis of the Rotterdam Study did not find an association. Furthermore, the Rotterdam Study and the Barbados Eye Study, which were large longitudinal population-based studies, did not identify diabetes as a risk factor for the incident development of glaucoma. In the OHTS, depending on how the analysis was performed, diabetes was either associated with a reduced risk of developing glaucoma or it was not associated with glaucoma. One possible explanation for these results is that the cohort of diabetic patients was skewed in this study because the presence of retinopathy was an exclusion criterion for participants in the OHTS.
de Voogd S, Ikram MK, Wolfs RC, et al. Is diabetes mellitus a risk factor for open-angle glaucoma? The Rotterdam Study. Ophthalmology. 2006;113(10):1827–1831.
The Baltimore Eye Survey found that systemic hypertension was associated with a lower risk of glaucoma in younger (<65 years) patients and a higher risk of glaucoma in older patients. The hypothesis is that younger individuals with high blood pressure may have better perfusion of the optic nerve, but as these patients age, their chronic hypertension may have adverse effects on the microcirculation of the optic nerve and increase its susceptibility to glaucomatous optic neuropathy. Conversely, in the Barbados Eye Study, the relative risk of developing glaucoma among study participants with systemic hypertension was less than 1 in all age groups, including those aged 70 years and older.
Lower ocular perfusion pressure
There is compelling evidence that lower ocular perfusion pressure (OPP; defined as diastolic blood pressure + 1/3 systolic blood pressure − IOP) is a risk factor for the development of glaucoma. The Baltimore Eye Survey found a sixfold increase in the prevalence of glaucoma in those patients with the lowest levels of OPP. Low systolic perfusion pressure was also a risk factor for glaucoma progression in the Early Manifest Glaucoma Trial (hazard ratio 1.42 for systolic perfusion pressure ≤160 mm Hg). Although the concept of OPP oversimplifies actual ocular blood flow, several factors, including autoregulatory mechanisms in central nervous system perfusion, make the association between OPP and glaucoma intriguing. The overtreatment of systemic hypertension may contribute to glaucoma progression and should be considered in some cases (eg, worsening of seemingly well-treated glaucoma).
Costa VP, Harris A, Anderson D, et al. Ocular perfusion pressure in glaucoma. Acta Ophthalmol. 2014;92(4):e252–e266.
Other associated conditions
Sleep apnea, thyroid disorders, hypercholesterolemia, migraine headaches, low cerebrospinal fluid pressure, and Raynaud phenomenon have been identified in 1 or more studies as potential risk factors for the development of glaucoma. Further research is required in order to clarify the significance of these conditions in patients with POAG and their relationship to glaucoma, if any.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.