Discrepancies found in IOP measurement methods among patients with thyroid-associated orbitopathy

In patients with thyroid-associated orbitopathy (TAO), the non-contact airpuff tonometer (NCT) significantly overestimates intraocular pressure (IOP) values compared to the Goldmann applanation tonometer (GAT) and the iCARE rebound tonometer, according to a study. On the other hand, the iCARE rebound tonometer provides IOP measurements that are comparable to the gold standard GAT in these patients. This suggests that careful consideration should be given to the choice of tonometry method when measuring IOP in TAO patients, as the accuracy of measurements can vary among different tonometers.

A total of 98 eyes from 49 adult patients with TAO were examined. All patients had a history of mild to moderate TAO, evidence of thyroid disease, and no clinical signs or symptoms of active disease. Importantly, none of the patients exhibited diplopia in direct gaze direction.

The measurements were conducted using NCT, iCARE, and GAT, with the results revealing notable differences. The mean IOP was recorded as 18.1 ± 2.4 mmHg with GAT, 22.3 ± 5.0 mmHg with NCT, and 18.0 ± 2.4 mmHg with iCARE.

Bland-Altman analysis indicated a negligible mean difference of -0.1 ± 1.16 mmHg between GAT and iCARE measurements, suggesting comparable results. However, the mean difference between GAT and NCT measurements was 4.2 ± 3.6 mmHg, signifying a significant overestimation by NCT. Similarly, the mean difference between iCARE and NCT measurements was -4.3 ± 3.7 mmHg, again indicating a significant discrepancy.

Statistical analysis confirmed no significant difference between GAT and iCARE, while there was a substantial difference between GAT and NCT and iCARE and NCT.

Reference
Karhanová M, Kalitová J, Malušková M, et al. Comparison of Three Methods of Tonometry in Patients with Inactive Thyroid-Associated Orbitopathy. Cesk Slov Oftalmol. 2023 Fall;79(6):318-323. English. doi: 10.31348/2023/38. PMID: 38086704.