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Frequently Asked Questions
Measurement Parameters
- What is Hysteresis?
- What is the difference between viscous and elastic resistance?
- How is Corneal Hysteresis measured?
- What is Corneal Hysteresis
- What is IOPg?
- Is IOPg different from the IOP value presented by a traditional Non-Contact Tonometer (NCT)?
- Is there a massage effect caused by repeated measurements with the Ocular Response Analyzer?
- What is IOPcc?
- How is IOPcc measured?
- What is CRF?
- What is the range of Corneal Hysteresis in normal Subjects?
- What is the range of Corneal Resistance Factor (CRF) in normal subjects
- What is the average value of Corneal Hysteresis in normal subjects?
- What is the average value of Corneal Resistance factor (CRF) in normal subjects?
- Are CH and CRF Related to the “Modulus of Elasticity” of the cornea?
- What is the acceptable repeat measurement variability for the corneal hysteresis measurement?
- What is the acceptable repeat measurement variability for the corneal resistance factor (CRF) measurement?
- Why is IOPg higher/lower than my Goldmann IOP value?
- How do Corneal Hysteresis (CH) and Corneal Reistance Factor (CRF) differ?
- Corneal hysteresis is a measure of the VISCOUS DAMPING in the corneal tissue. It is the "energy absorption capability" of the cornea.
*CH= P1 - P2
*CH is not strongly correlated with IOP.
Corneal Resistance Factor is an indicator of the total corneal response, including the ELASTIC RESISTANCE of the corneal tissue.
*CRF = P1 - (0.7*P2)
*It is strongly correlated with IOP measurements because a tonometer must overcome the static resistance of the cornea.
- Is Corneal Hysteresis (CH) related to Central Corneal Thickness (CCT)?
Interpreting results
- What is the average value of Corneal Hysteresis in normal subjects?
- What is the acceptable repeat measurement variability for the corneal hysteresis measurement?
- What is the acceptable repeat measurement variability for the corneal resistance factor (CRF) measurement?
- Why is IOPg higher/lower than my Goldmann IOP value?
- What are the characteristics of a "good" measurement signal for a normal subject?
- How can I tell a "bad signal" from a "good signal"?
Using the instrument
- What is the acceptable repeat measurement variability for the corneal hysteresis measurement?
- What is the acceptable repeat measurement variability for the corneal resistance factor (CRF) measurement?
- Why is IOPg higher/lower than my Goldmann IOP value?
- Why are the average values in the software different from the true mathematical average?
- Where are the results saved when I use the pachymeter?
- Should I use anesthesia before taking an Ocular Response Analyzer measurement?
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