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Frequently Asked Questions
Measurement Parameters
- What is Hysteresis?
- The phenomenon was identified, and the term coined, by Sir James Alfred Ewing in 1890.
Hysteresis is a property of physical systems that do not instantly follow the forces applied to them, but react slowly, or do not return completely to their original state.
The Merriam-Webster Dictionary defines hysteresis as a lagging or retardation of the effect, when the forces acting upon a body are changed, as if from velocity or internal friction; a temporary resistance to change from a condition previously induced, observed in magnetism, thermoelectricity, etc., on reversal of polarity.
Etymology: New Latin, from Greek hysteresis shortcoming, from hysterein to be late, fall short, from hysteros.
- 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?
- 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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