Abstract
Purpose :
Corneal hysteresis (CH) is a measure of the biomechanical properties of the cornea. Within the last few years the ability to measure this value has become commercially available with the Ocular Response Analyzer (ORA)(Reichart). Since CH has been described as both associated with glaucoma progression and a risk factor for developing glaucoma, reliability of data collection is paramount. Measurement with this device gives a measure of reliability in the form of a wavefrom score (WS). One previous study suggested that a WS value of less than 3.7 should be ignored, while others use different cutoffs such as 5, or list in their methods “good quality” results without quantifying the score used. We set out to see if there was a correlation between optic nerve head cupping and hysteresis in a glaucomatous population and whether or not that correlation was impacted at different WS measurements.
Methods :
This was a multicenter study with data collection from 2 sites. Patients who had been previously diagnosed with glaucoma, or who were glaucoma suspects had their intraocular pressure (IOP), CH and WS measured on the ORA. A dilated fundus exam was done and the cup to disk ratio was determined. Pearson correlations were evaluated on all patients with a WS of 0+, 1+, 2+...9+ for CH and optic nerve head cupping.
Results :
136 Glaucomatous or glaucoma suspect eyes were enrolled, CH correlation with cupping was apparent for all groups with a WS of at least 4. As WS increased, a stronger correlation was also noted. The attached table, has detailed N, R, and P values for each of 10 tested WS parameters. A WS of less than 4 showed no correlation, The cohorts with a WS of 4+ to 8+ had a statistically significant weak correlation, and WS of 8+ had a similar correlation but an N too low to show statistical significance.
Conclusions :
Optic nerve head cupping was similarly correlated for all values of WS of 4+. As WS increased, the correlation became stronger. We were able to confirm that CH can be helpful in glaucoma diagnosis due to its correlation to optic nerve head cupping but that this is only valuable if the reliability is high enough to be useful. Clinically this demonstrates that if using the ORA, if a measurement has a WS of less than 4, the data is likely not reliable and should be repeated.
This is a 2020 ARVO Annual Meeting abstract.