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Open Angle Glaucoma
Aka: Open Angle Glaucoma, Primary Open-Angle Glaucoma, POAG
- See Also
- Glaucoma
- Narrow Angle Glaucoma
- Epidemiology
- Most common type of Glaucoma (89%)
- Lifetime Prevalence: 10% of U.S. population (50% are unaware of diagnosis)
- More common in older patients
- Rare under age 40 years
- Prevalence among those over 80 years old: 14%
- However most undiagnosed Glaucoma is at age <60 years old
- Risk Factors
- Increasing age
- Odds Ratio increases 1.6 to 2.2 per decade of life
- Prevalence at age 40-49 years old
- Black: 1.3 to 1.4%
- Hispanic: 0.5 to 1.3%
- Caucasian: 0.2 to 0.5%
- Prevalence at age >80 years old
- Black: 11.3 to 23.2%
- Hispanic: 12.6 to 21.8%
- Caucasian: 1.9 to 11.4%
- Ethnicity or Race
- See age related Prevalence above
- Black patients
- Relative Risk: 3.5 to 4 fold increase in Glaucoma risk over caucasian patients
- Hispanic Patients
- Relative Risk: 2 fold increase in Glaucoma risk over caucasian patients
- First Degree Relative with Glaucoma (4-16% Risk)
- Sibling Relative Risk: 3.7 to 16
- Child or parent Relative Risk: 1.1 to 2.2
- Specific Glaucoma related genetic mutation accounts for <5% of cases
- Diabetes Mellitus
- Relative Risk: 1.4 to 1.5
- Severe Myopia (Nearsightedness)
- Eye Injury
- Eye Trauma
- Uveitis
- Corticosteroids (especially intra- and periocular)
- Pathophysiology
- Increased Aqueous Humor production
- Aqueous outflow obstruction by microscopic blockages
- Normal chamber angles
- Symptoms
- Bilateral eyes affected but asymmetrically
- Colored halos around lights
- Asymptomatic until severe Visual Field or central loss
- Visual Field loss irreversible unless caught early
- Compensation from opposite eye masks earlier visual changes
- Insidious painless Vision Loss
- Peripheral Vision Loss progresses to blindness
- Loss not symptomatic until 40% of nerve fibers lost
- Signs
- Pupil dilatation
- Increased Intraocular Pressure (by Tonometer)
- IOP < 22 mmHg: Normal if optic disks normal
- IOP 22-30 mmHg: Borderline
- IOP >31 mmHg: Abnormal
- Progressive peripheral Vision Loss
- Stages of Vision Loss
- Stage 1: Loss of nasal and superior Visual Field
- Stage 2: Loss of peripheral Visual Field
- Stage 3: Total blindness
- Screen Visual Fields by confrontation
- Perimetry offers computerized Visual Field evaluation
- Glaucomatous changes in the optic disc
- General
- Focal thinning of neural rim
- Nerves at edge of cup and edge of disc
- Thinning seen at temporal (lateral) disc margin
- Superficial Hemorrhage overlying disc edge
- Diagnostic changes
- Symmetrically enlarged cup-to-disc ratio >0.5 or
- Cup-to-disc ratio difference between eyes >0.2 or
- Significantly asymmetric cup in one eye
- Diagnosis
- Formal Open Angle Glaucoma diagnosis requires a combination of findings
- IOP measurement
- Stereoscopic Optic Nerve exam
- Visual Field testing
- Intraocular Pressure alone is not sufficient for diagnosis
- Normal Intraocular Pressure in 50% of POAG
- Most patients with Intraocular Pressure >22 mm Hg do not develop Glaucoma (with Optic Nerve injury)
- Screening is not recommended to be performed in primary care (USPTF)
- Combination of factors needed for diagnosis (see signs above)
- Typically performed by eye specialists
- Differential Diagnosis
- Acute Angle Closure Glaucoma
- Presents as a painful Red Eye
- Requires immediate evaluation and management
- Management
- General
- Regular aerobic Exercise reduces Intraocular Pressure
- Emphasize Medication Compliance (<50% continue medications >1 year)
- Simplify regimens as much as possible
- Approach treatment in similar fashion to systemic Hypertension Management
- Start with initial first-line agents
- Advance first-line agents
- Add additional medications as needed for persistent elevated pressures
- First Line Agents
- Prostaglandin Analogues (Latanoprost, Travoprost, Bimatoprost, Tafluprost, Unoprostone)
- Once daily, effective agent with low side effects
- Latanoprost (Xalatan) 0.005% one drop daily
- Intraocular Beta Blockers (Betaxolol, Carteolol, Levobunolol, Metipranolol, Timolol)
- Less expensive than other Glaucoma medications
- Consider other medications if higher risk for adverse effects
- Systemic Beta Blocker use
- Beta Blockers otherwise contraindicated (e.g. COPD, Asthma)
- More adverse effects
- Due to Beta Blocker systemic absorption with Hypotension and bronchoconstriction risk
- See Don't Open Eyes Technique for Eye Drop Instillation (to reduce systemic absorption)
- Second Line Agents
- Intraocular Cholinergics (Pilocarpine, Carbachol)
- Adjunctive Agents
- Intraocular Sympathomimetic (Dipivefrin, Propine)
- Topical Carbonic Anhydrase Inhibitor (Brinzolamide, Dorzolamide)
- Intraocular Alpha-Adrenergic (Apraclonidine, Brimonidine)
- Acute exacerbations of refractory chronic Glaucoma
- Systemic Carbonic Anhydrase Inhibitor
- Combination agents to consider
- Dorzolamide and Timolol Maleate (Cosopt, generic)
- Brinzolamide and Brimonidine (Simbrinza, expensive)
- Brimonidine and Timolol (Combigen, expensive)
- Surgery for refractory cases
- Laser trabeculoplasty
- May be used as first line therapy (esp. for patients non-compliant with topical drops)
- Surgical trabeculectomy
- Higher risk procedure used as last available option
- Prevention
- See Preventive Eye Examination for Glaucoma screening intervals
- References
- Alward (1998) N Engl J Med 339:1298-307 [PubMed]
- Distelhorst (2003) Am Fam Physician 67(9):1937-50 [PubMed]
- Gupta (2016) Am Fam Physician 93(8):668-74 [PubMed]
- Infeld (1998) Postgrad Med 74:709-15 [PubMed]
- Pelletier (2016) Am Fam Physician 94(3):219-26 [PubMed]