What is Open-Angle Glaucoma
Open-angle glaucoma (OAG) is a progressive, chronic optic neuropathy characterized by optic nerve damage and visual field loss, typically associated with elevated intraocular pressure, that often remains asymptomatic until significant irreversible vision loss has occurred. 1
Disease Definition and Pathophysiology
Primary open-angle glaucoma (POAG) is fundamentally an optic neuropathy, not simply a disease of elevated eye pressure. 2 The condition involves progressive damage to the optic nerve with characteristic enlarging optic disc cupping and peripheral visual field loss. 3 Importantly, elevated intraocular pressure (IOP) is a strong modifiable risk factor but not diagnostic—some patients have normal IOP (normal-pressure glaucoma) while others with elevated IOP never develop glaucoma (glaucoma suspects). 3
The disease is bilateral but typically asymmetric, progressing at different rates in each eye. 4
Epidemiology and Disease Burden
Global and U.S. Prevalence
- An estimated 76 million people worldwide had glaucoma in 2020, projected to increase 50% to 79.8 million by 2040 as populations age. 1
- In the United States, POAG prevalence among adults aged 40 and older was approximately 3.05% in 2013. 1
- Glaucoma is the second leading cause of blindness worldwide. 1
High-Risk Populations
African Americans face a threefold higher prevalence of OAG compared to non-Hispanic whites and it is the leading cause of blindness in this population. 1 The prevalence is even higher in Afro-Caribbeans than African Americans. 1
Hispanic/Latino populations have high OAG prevalence rates comparable to African Americans. 1
Asian Americans demonstrate prevalence rates comparable to Latinos and higher than non-Hispanic whites. 1
Age-Related Risk
The disease prevalence increases substantially with age, particularly after age 40. 5 Blacks older than 40 years and whites older than 65 years are at increased risk. 3
Clinical Presentation
Asymptomatic Nature
More than half of patients with POAG are asymptomatic, and extensive permanent optic nerve damage can occur before patients become aware of visual field loss. 6, 2 This lack of early symptoms means many patients are unaware they have a vision-threatening condition. 1
Progressive Vision Loss
The disease causes progressive loss of peripheral vision, which leads to:
- Difficulty with driving, particularly at night 2
- Increased risk of falls and subsequent fractures 2
- Higher risk of motor vehicle collisions in patients with severe visual field defects 1
Diagnostic Features
Structural Changes
A cup-to-disc ratio greater than 0.6 on ophthalmoscopy is suspicious for glaucoma. 2 Optic disc imaging, retinal nerve fiber layer (RNFL) imaging, and macular imaging enable detection of definite abnormalities consistent with glaucoma even before visual field changes manifest. 5
Functional Assessment
Standard automated perimetry (SAP) remains the gold standard for functional assessment, showing characteristic peripheral visual field loss. 5, 2 Formal visual field testing (perimetry) is a mainstay of glaucoma diagnosis and management. 3
Severity Staging
The American Academy of Ophthalmology establishes three severity classifications: 5
- Early stage: Definite structural abnormalities with normal visual fields
- Moderate stage: Structural abnormalities with visual field defects in one hemifield not within 5 degrees of fixation
- Severe stage: Structural abnormalities with bilateral hemifield defects and/or loss within 5 degrees of fixation
Additional Risk Factors
Beyond age and ethnicity, established risk factors include: 5
- Thin central cornea
- Myopia (particularly severe myopia) 3
- Type 2 diabetes mellitus
- Low ocular perfusion pressure
- Disc hemorrhage
- Family history of glaucoma 3
Impact on Quality of Life and Mortality
Visual impairment from glaucoma has been associated with: 1
- Cognitive decline and Alzheimer's disease
- Increased risk of mortality in older adults
- Reduced life satisfaction and mental health
- Decreased participation in home and community activities
Economic Burden
Annual direct medical costs escalate dramatically with disease progression, ranging from $623 for early glaucoma to $2,511 for end-stage disease. 5 Lifetime costs for glaucoma patients average $1,688 higher than patients without the condition. 5
Critical Clinical Pitfall
Without treatment, open-angle glaucoma leads to irreversible vision loss and blindness. 3 The asymptomatic nature combined with irreversible damage underscores the importance of early detection through routine comprehensive eye examinations, particularly in high-risk populations, rather than waiting for symptoms to develop.