Abstract
Purpose :
Numerous well-established sources of error contribute to intra-operator and inter-operator variability in Goldmann tonometry (GAT). There is unmet need for a tonometer that provides consistent intraocular pressure (IOP) measurements when taken by the same operator multiple times and when taken by different operators. This two-part study compared the intra-operator variability of IOP measurements taken with Goldmann and iCare tonometry, and evaluated the inter-operator agreement of IOP measurements taken with the iCare tonometer.
Methods :
In Part 1, an experienced ophthalmic technician obtained 5 masked GAT readings from 1 eye and 5 masked iCare readings from the fellow eye of 29 open-angle glaucoma (OAG) patients. For masking, an observer recorded each measurement and set the GAT dial back to 10 and cleared the iCare memory between readings. The variances of GAT and iCare measurements were compared with an F test; the sample size provided adequate power to detect a 25% difference in variance between instruments. In Part 2, 3 experienced technicians obtained 3 masked iCare readings from each eye of 19 OAG patients (different patients from the Part 1 sample). The intraclass correlation coefficient (ICC) assessed inter-technician agreement; the sample size provided adequate power to distinguish between an ICC of 0.75 (modest agreement) and 0.9 (excellent agreement).
Results :
In Part 1, iCare readings were more consistent than GAT readings (GAT variance 2.47, iCare variance 0.76, p=0.0035; 69% reduction in variance). In Part 2, iCare agreement among 3 technicians was excellent (ICC for right eyes 0.899, 95% confidence interval 0.784-0.958; ICC for left eyes 0.913, 95% confidence interval 0.815-0.964).
Conclusions :
iCare tonometry readings are more consistent than GAT, and the inter-operator agreement of iCare readings is excellent. An additional benefit of iCare over GAT is that iCare tonometry uses disposable probes that eliminate the risk of nosocomial infection, albeit at a higher cost. Overall, iCare tonometry may be a better method for IOP monitoring than Goldmann tonometry.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.