Tonopen Versus Goldmann Applanation Tonometry for Detecting Restrictive Thyroid Eye Disease

Purpose: In thyroid eye disease (TED), intraocular pressure (IOP) measurements are taken in both the primary and upgaze positions to elicit restrictive muscle disease. The aim of this study was to assess whether the IOP when measured with the eyes in upgaze (the Goldmann applanation tonometer [GAT] head applanating the inferior/peripheral cornea) is similar when compared with the central corneal IOP in upgaze using the Tono-Pen XL. Methods: IOP was measured with the GAT on the central cornea in primary gaze and on the inferior cornea in upgaze. IOP was measured with the Tono-Pen XL in the central cornea in both primary gaze and upgaze. The outcome measure was the difference in IOP readings between the GAT and the Tono-Pen XL for patients with restrictive TED. Results: Fifty-two patients were included in the study; 31 patients with restrictive TED and 21 control patients. In the control group, there was no significant difference in Tono-Pen XL and GAT readings for both primary gaze and upgaze (p = 0.99). Both instruments detected an increase in IOP with upgaze in patients with restrictive TED compared with controls (p = 0.0006). There was no significant difference between the 2 instruments' readings in upgaze for patients with restrictive TED (p = 0.39). Conclusions: Both the GAT and the Tono-Pen XL can be used to establish IOP in patients with restrictive TED.