Measurement of Intraocular Pressure: Tono-Pen Technique (Emergency Medicine)

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SAMPLE EXCERPT
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PRE-PROCEDURE
INDICATIONS
  • Confirmation of a clinical diagnosis of acute angle-closure glaucoma
  • Determination of a baseline ocular pressure after blunt ocular injury
  • Determination of a baseline ocular pressure in a patient with iritis
  • Documentation of ocular pressure in the patient at risk for open-angle glaucoma
CONTRAINDICATIONS
  • Tonometric examination, with the exception of the palpation technique (through the lids) and the noncontact method, should not be performed on a cornea without complete anesthesia.
  • Tonometry should not be performed with a suspected penetrating ocular injury.
  • The presence of corneal defects represents a relative contraindication to tonometry.
  • Patients who cannot maintain a relaxed, immobile position
EQUIPMENT
  • Tono-Pen or Tono-Pen XL (Reichert, Inc, Depew, NY)
    • Disposable latex covers
  • Topical ocular anesthetic (e.g., tetracaine, proparacaine)
ANATOMY
  • Just beneath the cornea and anterior to the iris is the fluid-filled anterior chamber.
  • Aqueous flow
    • Aqueous humor is produced in the nonpigmented cells of the ciliary body.
    • This fluid travels between the posterior surface of the iris and anterior surface of the lens, through the pupil, and out of the eye via the trabecular outflow path and the uveoscleral path.
    • Elevated intraocular pressure occurs when aqueous outflow is impaired.
    • Low intraocular pressure can be due to either a decrease in aqueous production (e.g., uveitis) or an increase in aqueous outflow (e.g., ruptured globe).

PROCEDURE
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The full content of this section includes:
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  • Links to medical evidence and related procedures

POST-PROCEDURE
CARE
  • Intraocular pressure should be reduced by topical medications such as latanoprost, timolol, brimonidine tartrate, and dorzolamide see.
  • Oral agents (acetazolamide 250 mg tablets, 2 by mouth) or intravenous agents (mannitol; dosing varies by body weight) should be reserved for situations in which topical agents do not control intraocular pressure.
  • Anterior chamber paracentesis is not recommended.
COMPLICATIONS
  • Complications are unusual.
  • Additional trauma can occur in an eye with preexisting corneal injury.
  • Corneal abrasions can be produced by ocular movement during testing.
  • Infection can be transmitted by the use of the instrument.
  • Extrusion of ocular contents with penetrating injuries is a potential but rare complication.
RESULT ANALYSIS
  • IOP 0-8 mm Hg: Recheck IOP; if results are replicated, consult with an ophthalmologist.
  • IOP 9-21 mm Hg: routine follow up with an ophthalmologist
  • IOP 22-30 mm Hg: If otherwise asymptomatic, the patient should follow up with an ophthalmologist within 2 weeks.
  • IOP ≥30 mm Hg: requires urgent consultation with an ophthalmologist and initiation of therapy
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