Does the new corneal visualization with Scheimpflug technology (CorVis ST) match well with the Goldmann applanation tonometry (GAT) or agree better with ocular response analyzer (ORA)

Poster Details

First Author: S.Tejwani INDIA

Co Author(s):    S. D'souza   A. Joshi   S. Devi   M. Kumar   R. Shetty  

Abstract Details

Purpose:

1. To establish the agreement and correlation of intraocular pressure (IOP) measurements by CorVis ST with that done by GAT 2. To establish agreement and correlation between IOPcc of ORA and IOP measured by GAT 3. To compare CorVis ST with ORA as both the instruments take in to account the corneal biomechanics while measuring the IOP

Setting:

Tertiary eye care centre in southern India.

Methods:

Eighty eyes of 42 patients visiting glaucoma clinic at a tertiary eye care centre were studied prospectively. Of these 50 eyes were of 27 glaucoma patients on treatment. All patients underwent intraocular pressure measurement using Goldman applanation tonometer, CorVis ST of Occulus, and Ocular response analyzer of Reichert. The patients that could not perform either of the tests were excluded from the analysis. Bland Altman analysis was then done to compare the GAT with CorVis, GAT with IOPcc of ORA, and also CorVis with IOPcc of ORA. Correlation coefficient was also calculated for comparing all the three tonometers. Also the analysis was done separately also for glaucoma patients.

Results:

Eighty eyes of 42 patients were analyzed to compare the IOP reading with different tonometers. The pearson’s correlation between GAT and CorVis showed the r value of 0.65 with 95% confidence interval (CI) of 0.50 to 0.76 (p<0.0001), the bias for agreement was 1.24, and 95% limits of agreement were -5.60 to 8.09.The correlation for GAT and IOPcc of ORA showed an r=0.53 with 95%CI of 0.35 to 0.67(p<0.0001), the bias of agreement was 4.41with limits of agreement being -4.99 to 13.82. The correlation between CorVis and ORA demonstrated the r=0.72 with 95% CI of 0.60 to 0.81, the bias for agreement was 3.17 with 95% limits of agreement being -4.25 to 10.11. The glaucoma group of 50 eyes was analyzed separately showed correlation of r=0.59 for GAT versus CorVis, 95% CI 0.38 to 0.75, the agreement had a bias of1.55 with 95% limits of agreement of -6.44 to 9.54. The GAT and IOPcc of ORA showed the r=0.52 (95% CI: 0.28-0.69) and agreement bias of 5.45 with wide limits of agreement i.e. -4.27 to 15.18.CorVis and ORA had r= 0.70 (95% CI 0.52 -0.82) and an agreement bias of 3.90 with 95%limits of agreement being -3.97 to 11.78.

Conclusions:

The correlation of IOP measurements obtained by CorVis and ORA were found to be good with Goldmann Applanation tonometer, however the agreement ranges of these instruments with GAT are very wide much beyond the level of clinical significance. Even the ORA and the CorVis, both the machines that consider corneal biomechanical properties into consideration while obtaining IOP did not show agreement. This suggests that all three machines have a good correlation with each other but they cannot be used interchangeably as each one takes the different parameters into account while measuring IOP. FINANCIAL DISCLOSURE?: No