Norm of Pachymetry Test for Corneal Thickness
Average central corneal thickness = 540–555 μm.
Usage of Pachymetry Test for Corneal Thickness
Screening for eligibility for laser eye surgery; detection of clients at higher risk for open-angle glaucoma because of thinner than normal corneas. Also is recommended for glaucoma screening in clients who have previously had laser eye surgery.
Description of Pachymetry Test for Corneal Thickness
The pachymetry test uses a hand-held ultrasonic device, called a pachymeter, to gauge central corneal thickness. Corneal thickness information is essential in determining eligibility for laser eye surgery (refractive surgical procedures), because the surgery reduces corneal thickness. In these clients, pachymetry assures that a minimal amount of central cornea is present in order to prevent an abnormal bowing of the corneas postoperatively. Clients who have previously had laser eye surgery are at risk for a false-negative tonometry test (see Tonometry test for glaucoma) because their surgically thinned corneas may test low.
Professional Considerations of Pachymetry Test for Corneal Thickness
Consent form NOT required.
- Obtain eye drops to localize the cornea.
- Instill eye drops in each eye to be tested.
- Place measurement device on eye.
- Three separate measurements (on each eye) are taken, and an average value is obtained.
- No special care needed.
Client and Family Teaching
- Use eyewear protection until eye sensation returns.
- Measurements assist in glaucoma therapy.
- This test is noninvasive.
Factors That Affect Results
- Clients with thin corneas may demonstrate artificially lower intraocular pressure measurements than actually exist.
- Clients with thicker corneas may demonstrate artificially higher intraocular pressure measurements than actually exist.
- Corneal edema causes a higher than normal reading.