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?

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?

In order for the CCT results to be archived, the pachymeter must be used only after taking an IOP/CH measurement.  Once the necessary patient data has been entered and the IOP/CH has been taken for the desired eye(s), then the CCT can be taken.  The data will be stored alond with all of the other measurement data.

The pachymeter can be used to take a stand-alone CCT measurement.  The results will be displayed on the screen, but they will not be saved unless the IOP/CH data has been collected first.

Should I use anesthesia before taking an Ocular Response Analyzer measurement?