Open Angle Glaucoma

1. See Also
   1. Glaucoma
   2. Narrow Angle Glaucoma
2. Epidemiology
   1. Most common type of Glaucoma (89%)
   2. Lifetime Prevalence: 10% of U.S. population (50% are unaware of diagnosis)
   3. More common in older patients
      1. Rare under age 40 years
      2. Prevalence among those over 80 years old: 14%
3. Risk Factors
   1. Increasing age
      1. Black race: Over age 40 years
      2. Caucasian: Over age 65 years
   2. Black Race
      1. Relative risk: 4 fold increase in Glaucoma risk
   3. First Degree Relative with Glaucoma (4-16% Risk)
      1. Relative risk: 7 fold increase in Glaucoma risk
   4. Diabetes Mellitus
   5. Severe Myopia (Nearsightedness)
   6. Eye Injury
      1. Eye Trauma
      2. Uveitis
      3. Corticosteroids (especially intra- and periocular)
4. Pathophysiology
   1. Increased Aqueous Humor production
   2. Aqueous outflow obstruction by microscopic blockages
   3. Normal chamber angles
5. Symptoms
   1. Bilateral eyes affected but asymmetrically
   2. Colored halos around lights
   3. Asymptomatic until severe visual field or central loss
      1. Visual field loss irreversible unless caught early
      2. Insidious painless Vision Loss
         1. Peripheral Vision Loss progresses to blindness
         2. Loss not symptomatic until 40% of nerve fibers lost
6. Signs
   1. Pupil dilatation
   2. Increased Intraocular Pressure (by Tonometer)
      1. IOP < 22 mmHg: Normal if optic disks normal
      2. IOP 22-30 mmHg: Borderline
      3. IOP >31 mmHg: Abnormal
   3. Progressive peripheral Vision Loss
      1. Stages of Vision Loss
         1. Stage 1: Loss of nasal and superior visual field
         2. Stage 2: Loss of peripheral visual field
         3. Stage 3: Total blindness
      2. Screen visual fields by confrontation
      3. Perimetry offers computerized visual field evaluation
   4. Glaucomatous changes in the optic disc
      1. General
         1. Focal thinning of neural rim
            1. Nerves at edge of cup and edge of disc
            2. Thinning seen at temporal (lateral) disc margin
         2. Superficial hemorrhage overlying disc edge
      2. Diagnostic changes
         1. Symmetrically enlarged cup-to-disc ratio >0.5 or
         2. Cup-to-disc ratio difference between eyes >0.2 or
         3. Significantly asymmetric cup in one eye
7. Differential Diagnosis
   1. Acute Angle Closure Glaucoma
      1. Presents as a painful red eye
      2. Requires immediate evaluation and management
8. Management
   1. Lifestyle changes
      1. Regular aerobic Exercise reduces Intraocular Pressure
   2. First Line Agents
      1. Prostaglandin Analogues (Latanoprost, Travoprost, Bimatoprost)
         1. Once daily, effective agent with low side effects
      2. Intraocular Beta Blockers (Betaxolol, Carteolol, Levobunolol, Metipranolol, Timolol)
         1. Less expensive, but more adverse effects
         2. Consider other meds if on systemic Beta Blocker
   3. Second Line Agents
      1. Intraocular Cholinergics (Pilocarpine, Carbachol)
   4. Adjunctive Agents
      1. Intraocular Sympathomimetic (Dipivefrin, Propine)
      2. Topical Carbonic Anhydrase Inhibitor (Brinzolamide, Dorzolamide)
      3. Intraocular Alpha-Adrenergic (Apraclonidine, Brimonidine)
   5. Acute exacerbations of refractory chronic Glaucoma
      1. Systemic Carbonic Anhydrase Inhibitor
   6. Combination agents to consider
      1. Dorzolamide with Timolol Maleate (Cosopt)
   7. Surgery for refractory cases
      1. Laser trabeculoplasty
         1. May be used as first line therapy
      2. Surgical trabeculectomy
         1. Higher risk procedure used as last available option
9. Prevention
   1. See Preventive Eye Examination for Glaucoma screening intervals
10. References
    1. Alward (1998) N Engl J Med 339:1298-307
    2. Distelhorst (2003) Am Fam Physician 67(9):1937-50
    3. Infeld (1998) Postgrad Med 74:709-15