Pachymetry

Synonym/Acronym:
N/A

Rationale
To assess the thickness of the cornea prior to LASIK surgery and evaluate glaucoma risk.

Patient Preparation
There are no food, fluid, activity, or medication restrictions unless by medical direction.

Normal Findings

  • Normal corneal thickness of 535 to 555 micron.

Critical Findings and Potential Interventions
N/A

Overview

(Study type: Sensory, ocular; related body system: Nervous system.) Pachymetry is the measurement of the thickness of the cornea using an ultrasound device called a pachymeter. Refractive surgery procedures such as LASIK (laser-assisted in situ keratomileusis) remove tissue from the cornea. Pachymetry is used to ensure that enough central corneal tissue remains after surgery to prevent ectasia, or abnormal bowing, of thin corneas. Also, studies point to a correlation between increased risk of glaucoma and decreased corneal thickness. This correlation has influenced some health-care providers (HCPs) to include pachymetry as part of a regular eye health examination for patients who have a family history of glaucoma, have high blood pressure, or are part of a high-risk population. People of African descent have a higher incidence of glaucoma than any other ethnic group.

Indications

  • Assist in the diagnosis of glaucoma (Note: The intraocular pressure in glaucoma patients with a thin cornea, 530 micron or less, may be higher than in patients whose corneal thickness is within normal limits).
  • Determine corneal thickness in potential refractive surgery candidates.
  • Monitor the effects of various therapies using eyedrops, laser, or filtering surgery.

Interfering Factors

Factors that may alter the results of the study

  • Improper technique during application of the probe tip to the cornea.

Potential Medical Diagnosis: Clinical Significance of Results

Abnormal Findings In:

  • Bullous keratopathy
  • Corneal rejection after penetrating keratoplasty
  • Fuchs endothelial dystrophy
  • Glaucoma

Nursing Implications

Before the Study: Planning and Implementation

Teaching the Patient What to Expect

  • Inform the patient this procedure can assist in measuring the thickness of the cornea in the eye.
  • Review the procedure and address concerns about pain.
  • Explain that some discomfort may be experienced after the test when the numbness wears off from anesthetic drops administered prior to the test, or discomfort may occur if too much pressure is used during the test.
  • Explain that the test evaluates both eyes and takes about 3 to 5 min.
  • Positioning for this study is comfortably seated.
  • Explain that topical anesthetic drops will be instilled in each eye and allowed time to work.
  • Advise the patient that it will be important to look straight ahead, unblinking, and keep the eyes open while the probe of the pachymeter is applied directly on the cornea of the eye.
  • An average of three readings are taken for each eye. Individual readings should be within 10 microns. Results on both eyes should be similar.

Potential Nursing Actions

  • Obtain a history of known or suspected visual impairment, including type and cause (e.g., dry eye, narrow-angle glaucoma); eye conditions with treatment regimens; eye surgery; changes in visual acuity; and use of glasses or contact lenses.
  • Instruct the patient to remove contact lenses or glasses, as appropriate.

After the Study: Potential Nursing Actions

Treatment Considerations

  • Anticipate anxiety related to test results and provide teaching related to the clinical implications of the test results.
  • Encourage the family to recognize and be supportive of impaired activity related to vision loss, anticipated loss of driving privileges, or the possibility of requiring corrective lenses (self-image).
  • Discuss the implications of test results on lifestyle choices.
  • Provide reassurance regarding concerns related to impending corneal surgery.

Followup Evaluation and Desired Outcomes

  • Acknowledges contact information provided for patient education on the topic of eye care, such as the American Academy of Ophthalmologists (www.aao.org), American Optometric Association (www.aoa.org), or All About Vision (www.allaboutvision.com).
  • Acknowledges contact information provided for the Glaucoma Research Foundation (www.glaucoma.org).

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