When gold standards change: time to move on from Goldmann tonometry?

The English ophthalmologist Richard Banister was one of the first to report palpable hardness of the normal-appearing eye in 1622.1 Tonometry is an essential measurement in the assessment of eye health and a key component of glaucoma diagnosis and treatment, with intraocular pressure (IOP) remaining the only modifiable risk factor for glaucoma.2 Goldmann applanation tonometry (GAT) is the currently accepted ‘gold standard’ and approximates IOP by measuring the force needed to flatten a fixed area at the corneal apex.3 4 To do so, GAT makes important assumptions about corneal thickness and behaviour, assumptions that are not met in a significant proportion of patients.5 GAT has been used for nearly 70 years and is considered the reference standard4 for IOP measurement largely owing to the fact that nearly all clinical trial protocols have relied on GAT. The technique is widely integrated within clinical practice, and a certain amount of inertia has prevented clinicians from shifting to newer, possibly better, technologies. This resistance is perhaps analogous to the slow adoption of superior logarithm of the minimum angle of resolution measures of visual acuity, even when the limitations of Snellen were well established.6 The relatively low cost of GAT also contributes to its ongoing appeal. Yet GAT has significant limitations that make it a suboptimal, …