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SOURCE

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Source: Fiscella RG, Lesar TS, Owaidhah OA, Edward DP. Glaucoma. In: DiPiro JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM, eds. Pharmacotherapy: A Pathophysiologic Approach. 10th ed. New York, NY: McGraw-Hill; 2017. http://accesspharmacy.mhmedical.com/content.aspx?bookid=1861&sectionid=133893440. Accessed May 12, 2017.

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DEFINITION

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  • Ocular disorder leading to optic neuropathy characterized by changes in optic nerve head (optic disk) associated with loss of visual sensitivity and field.

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ETIOLOGY

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  • Inherited disorder, congenital, or secondary to disease, trauma, or drugs.

  • Secondary open-angle glaucoma caused by:

    • Exfoliation syndrome.

    • Pigmentary glaucoma.

    • Systemic diseases.

    • Trauma.

    • Surgery.

    • Ocular inflammatory diseases.

    • Drugs (Table 1)

  • Secondary glaucoma classified as:

    • Pretrabecular.

    • Trabecular.

    • Posttrabecular.

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Table Graphic Jump Location
TABLE 1.Drugs That May Induce or Potentiate Increased Intraocular Pressure in Open-angle Glaucoma
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PATHOPHYSIOLOGY

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  • Cause of optic neuropathy unknown.

    • Increased intraocular pressure (IOP)

    • Ischemia.

    • Excitotoxicity.

    • Autoimmune reactions.

    • Other abnormal physiologic processes.

  • Risk of visual field loss increases with increasing IOP.

    • IOP is not constant and changes with:

      • Pulse.

      • Blood pressure.

      • Forced expiration or coughing.

      • Neck compression.

      • Posture.

    • IOP demonstrates diurnal variation with minimum pressure around 6 P.M. and maximum pressure upon awakening.

    • IOP determined by balance between inflow and outflow of aqueous humor.

      • Inflow.

        • Increased by β adrenergic agents.

        • Decreased by α 2- and β adrenergic blockers, dopamine blockers, carbonic anhydrase inhibitors (CAIs), and adenylate cyclase stimulators.

      • Outflow.

      • Increased by cholinergic agents, prostaglandin analogs, and β and α 2-adrenergic agonists.

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EPIDEMIOLOGY

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  • Affects up to 4 million individuals in the US and 70 million individuals worldwide.

  • Second leading cause of blindness.

    • 135,000 people in the US have glaucoma-related bilateral blindness.

  • Incidence increases with increasing age as well as family history, thinner central corneal thickness, lower ocular perfusion pressure, type 2 diabetes, myopia, and certain genetic mutations.

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SCREENING

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  • Essential to early diagnosis.

    • Annual eye examinations recommended with family history of glaucoma and in diabetics.

    • IOP measurement and eye examinations recommended every 3–5 years for those older than 50 years.

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RISK FACTORS

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  • Ocular hypertension.

  • Increased IOP

  • Older age.

  • Family history of glaucoma.

  • Lower ocular perfusion pressure.

  • Lower blood pressure.

  • Thinner central cornea.

  • Optic disk hemorrhage.

  • Larger cup-to-disk ratio.

  • Specific visual field findings.

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CLINICAL PRESENTATION

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  • Slowly progressive and usually asymptomatic until onset of substantial visual field loss. Central visual acuity maintained, even in late stages.

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SIGNS AND SYMPTOMS
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