Diabetes significantly increases the risk for certain types of glaucoma and can directly cause the most severe form. Diabetes Mellitus is a chronic metabolic disorder defined by persistent high blood sugar (hyperglycemia), resulting from the body’s inability to produce or effectively use insulin. Glaucoma is a group of eye conditions that damage the optic nerve, which transmits visual information from the eye to the brain, often linked to elevated pressure inside the eye. People with diabetes are about twice as likely to develop glaucoma compared to the general population, making this one of the most serious long-term complications of the disease.
Understanding Diabetes and Glaucoma
Diabetes is characterized by high levels of glucose in the bloodstream, a state that over time damages blood vessels and nerves throughout the body. Type 1 diabetes involves an autoimmune destruction of insulin-producing cells, while Type 2 diabetes involves insulin resistance and a relative lack of insulin production.
Primary Open-Angle Glaucoma (POAG) occurs when the eye’s drainage system, the trabecular meshwork, becomes gradually clogged. The resulting fluid buildup increases the intraocular pressure (IOP), ultimately compressing the delicate nerve fibers of the optic nerve. While high IOP is the most recognized risk factor, damage can occur even with normal pressure, suggesting the optic nerve’s susceptibility also plays a role.
How Diabetes Increases General Glaucoma Risk
Chronic hyperglycemia creates a systemic environment of oxidative stress and chronic low-grade inflammation, which affects the eye’s delicate structures. This prolonged exposure to high blood sugar accelerates the formation of Advanced Glycation End products (AGEs) within the eye. These AGEs can compromise the function of the trabecular meshwork, the tissue responsible for draining fluid from the eye.
Damage to the trabecular meshwork causes fibrosis and stiffness, which increases resistance to the outflow of aqueous humor and leads to chronically elevated IOP. Diabetes also damages the tiny blood vessels supplying the optic nerve, a process called vascular dysregulation. This reduced blood flow makes the optic nerve more vulnerable to damage from intraocular pressure. Studies indicate that diabetes increases the risk of developing POAG by about 36 percent.
Neovascular Glaucoma: The Direct Diabetic Complication
The most direct and severe form of glaucoma linked to diabetes is Neovascular Glaucoma (NVG), a secondary form resulting from advanced diabetic eye disease. NVG is a complication of Proliferative Diabetic Retinopathy (PDR), where prolonged damage to the retinal blood vessels causes severe oxygen deprivation (ischemia) in the retina. The oxygen-starved retina responds by releasing excessive amounts of Vascular Endothelial Growth Factor (VEGF), a signal to grow new blood vessels.
These new vessels, called neovascularization, are abnormal, fragile, and grow into the front of the eye, across the iris, and into the drainage angle. The vessels and accompanying fibrous tissue rapidly block the trabecular meshwork, severely impeding fluid drainage. This blockage causes a sudden spike in intraocular pressure. This condition can lead to rapid, irreversible vision loss and is responsible for a significant portion of diabetes-related blindness.
Proactive Eye Health Management for Diabetics
Mitigating the risk of glaucoma and other eye complications begins with rigorous control of diabetes. Maintaining blood sugar levels close to the target A1C of 7% or less, and controlling blood pressure and cholesterol levels, are essential. These efforts slow the progression of microvascular damage that underlies both POAG risk and the development of Proliferative Diabetic Retinopathy.
A comprehensive, dilated eye examination by an ophthalmologist or optometrist is necessary at least once a year. This should start shortly after diagnosis for Type 2 diabetes and within five years for Type 1 diabetes. Dilation allows the doctor to thoroughly inspect the retina and optic nerve for the earliest signs of damage, often before any symptoms appear. Should early signs of diabetic eye disease be detected, treatments like laser therapy or anti-VEGF injections can be used to stabilize the retina, preventing progression to Neovascular Glaucoma.