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This website explores the agreement among the Goldmann Applanation Tonometer, Easyton Transpalpebral Tonometer, Tonopen, and Icare in Patients with Keratoconus
The study looked at how well four different devices measure eye pressure in people with keratoconus, a condition that changes the shape of the cornea. The devices were the Goldmann Applanation Tonometer (GAT), Easyton, Tonopen, and Icare.
The study included 46 eyes from 26 patients, with an average age of about 24 years. There were 15 men and 11 women in the group.
The Easyton device gave the highest average eye pressure readings (12.33 mmHg), followed by the Tonopen (11.59 mmHg), GAT (10.67 mmHg), and Icare (10.04 mmHg). The Easyton readings were significantly higher than those from GAT. However, there was no significant difference between the GAT readings and those from Tonopen or Icare. Also, there was no significant difference between Easyton and Tonopen readings.
The study also looked at how eye pressure measurements related to corneal thickness and shape. Icare readings were affected by the thickness and curvature of the cornea, while GAT readings were only affected by the maximum curvature of the cornea.
According to the Bland-Altman plots, 82.6% of the differences between GAT and Tonopen readings were within the acceptable range (±2 mmHg). This was true for 73.9% of the differences between GAT and Icare readings, and 78.3% for GAT and Easyton readings.
In summary, the Easyton device tends to give higher eye pressure readings compared to GAT, while Tonopen and Icare give similar readings to GAT. Among the devices, Tonopen had the closest agreement with GAT. This suggests that Tonopen and Icare are reliable alternatives to GAT for measuring eye pressure in patients with keratoconus, although Easyton may overestimate the pressure. This is important to know for doctors treating patients with this corneal condition.