Measuring intraocular pressure

Tonometry is undergoing a long-overdue renaissance. Goldmann applanation tonometry (GAT) is 50-year-old technology. Although GAT is considered a 'reference standard', it has many limitations and confounders. This review compares GAT to some of the newer technologies that have recently been commercialized or are in development.

Dynamic contour tonometry is fairly cornea-independent, but requires technical skill to carry out. Rebound tonometry requires no anesthetic and is particularly useful in children. The ocular response analyzer quantifies corneal biomechanical factors and provides other useful measures relevant to glaucoma risk. A transpalpebral tonometer that claims to measure intraocular pressure (IOP) through the closed eyelid has been introduced, but studies comparing it to conventional tonometers suggest it is too unreliable for routine use. Various new technologies including IOP-sensing contact lenses and implantable sensors are in clinical evaluation.

There is no perfect tonometer, and clinicians must choose which to use in their daily practice, balancing accuracy, precision, convenience, and cost. Clinicians should recognize that a single IOP measurement is but an often error-prone snapshot of a widely varying physiologic parameter. IOP data should only be used in the context of the overall clinical picture.