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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?
- Ocular Reponse Analyzer IOPg is strongly correlated to Goldmann and provides the same results on average. However, in some cases, there may be a significant difference between IOPg and GAT. Quite simply, different tonometers utilize different methods of operation and will respond to the cornea (and other factors involved in the IOP measurement process) differently. Therefore, it is normal to see slight differences between IOPg and Goldmann and even occasional large differences between the two devices.
If operators are noticing a systematic offset between IOPg and Goldmann (one is always higher or lower than the other) another issue may be at play. Consider the following possibilities:
- Goldmann is dependant on operator technique. Has the offset been validated using multiple operators?
- The Goldmann tonometer requires routine calibration. Is the device properly calibrated?
- Is the Goldmann "sticky"? Try another Goldmann tonometer
If these variables can be ruled, out and there is still a systematic bias in the measurement results, the Ocular Response Analyzer may need to be evaluated. Contact Reichert for further information.
- 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?
- Ocular Reponse Analyzer IOPg is strongly correlated to Goldmann and provides the same results on average. However, in some cases, there may be a significant difference between IOPg and GAT. Quite simply, different tonometers utilize different methods of operation and will respond to the cornea (and other factors involved in the IOP measurement process) differently. Therefore, it is normal to see slight differences between IOPg and Goldmann and even occasional large differences between the two devices.
If operators are noticing a systematic offset between IOPg and Goldmann (one is always higher or lower than the other) another issue may be at play. Consider the following possibilities:
- Goldmann is dependant on operator technique. Has the offset been validated using multiple operators?
- The Goldmann tonometer requires routine calibration. Is the device properly calibrated?
- Is the Goldmann "sticky"? Try another Goldmann tonometer
If these variables can be ruled, out and there is still a systematic bias in the measurement results, the Ocular Response Analyzer may need to be evaluated. Contact Reichert for further information.
- 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?
- Ocular Reponse Analyzer IOPg is strongly correlated to Goldmann and provides the same results on average. However, in some cases, there may be a significant difference between IOPg and GAT. Quite simply, different tonometers utilize different methods of operation and will respond to the cornea (and other factors involved in the IOP measurement process) differently. Therefore, it is normal to see slight differences between IOPg and Goldmann and even occasional large differences between the two devices.
If operators are noticing a systematic offset between IOPg and Goldmann (one is always higher or lower than the other) another issue may be at play. Consider the following possibilities:
- Goldmann is dependant on operator technique. Has the offset been validated using multiple operators?
- The Goldmann tonometer requires routine calibration. Is the device properly calibrated?
- Is the Goldmann "sticky"? Try another Goldmann tonometer
If these variables can be ruled, out and there is still a systematic bias in the measurement results, the Ocular Response Analyzer may need to be evaluated. Contact Reichert for further information.
- 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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