Glaucoma

Glaucoma

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Glaucoma, Increased Intraocular Pressure

  • See Also
  1. Open Angle Glaucoma
  2. Narrow Angle Glaucoma
  • Definitions
  1. Glaucoma
    1. Increased Intraocular Pressure AND Optic Nerve injury
    2. High risk of blindness if untreated (acuity <20/200)
  • Epidemiology
  1. Within top 3 causes of blindness in U.S.
    1. Leading cause of blindness in non-white
  2. U.S. Prevalence: 2 Million
    1. Only 50% are estimated to now be under treatment
    2. 120,000 are blind due to Glaucoma
    3. Highest risk groups for Glaucoma-related blindness in Blacks and Hispanics
  3. World Prevalence: 80 Million (estimated by 2020)
    1. Bilateral blindness due to Glaucoma estimated at 11 million worldwide by 2020
  • Pathophysiology
  1. Elevated Intraocular Pressure (IOP)
    1. Increased production of Aqueous Humor by ciliary body
      1. Aqueous Humor is typically produced at 2 ul/min
    2. Increased outflow resistance at Aqueous Outflow Angle
      1. Trabecular meshwork
      2. Canal of Schlemm
  2. Progressive changes in optic disc
    1. Nerve damage related to increased IOP is variable
      1. Glaucoma suspects (66% of those with high IOP)
        1. No damage despite high Intraocular Pressure (>21)
        2. Optic Nerve injury rate in suspects: 1% per year
      2. Normal-pressure Glaucoma (15% of Glaucoma patients)
        1. Normal Intraocular Pressure (21 mmHg or less)
        2. Glaucoma-related Optic Nerve damage
    2. Progressive Glaucomatous cupping at the optic disc
      1. IOP collapses Optic Nerve head structural support
      2. Axons destroyed by mechanical compression
  3. Peripheral Visual Field loss
    1. Open Angle Glaucoma: Slowly progressive
    2. Narrow Angle Glaucoma: Rapid Vision Loss
  • Types
  1. Primary Glaucoma
    1. Open Angle Glaucoma (89% of cases)
      1. Outflow blocked by microscopic outflow changes
      2. Results in progressive peripheral Vision Loss
      3. Usually asymptomatic until 40% of nerve loss
    2. Narrow Angle Glaucoma (11% of cases)
      1. Outflow tract blocked by base of iris
      2. Permanent Vision Loss may occur in hours
      3. Presents as acute painful Red Eye with Vomiting
  2. Secondary Glaucoma
    1. Medications that increase IOP in those predisposed
      1. Corticosteroids (Systemic and Topical)
        1. Reversible
      2. Mild Adrenergic or Anticholinergic Medications
        1. Examples
          1. Cold Medications
          2. Antidepressants
          3. Antidiarrheals
        2. Effect: Dilate Pupil
          1. Theoretically worsen angle closure Glaucoma
          2. Not contraindicated in Glaucoma
  • Resources
  1. Aging Eye Glaucomatrac (Glaucoma Management Tracking)
    1. http://www.agingeye.net/glaucomacharting.index
  2. Aging Eye Glaucoma Video
    1. http://www.agingeye.net/mainnews/video.php
  • References
  1. Alward (1998) N Engl J Med 339:1298-307 [PubMed]
  2. Distelhorst (2003) Am Fam Physician 67(9):1937-50 [PubMed]
  3. Gupta (2016) Am Fam Physician 93(8):668-74 [PubMed]
  4. Infeld (1998) Postgrad Med 74:709-15 [PubMed]