Pediatric intraocular pressure measurements: Tonometers, central corneal thickness, and anesthesia

Measuring intraocular pressure (IOP) is the cornerstone of a comprehensive glaucoma examination. In babies or small children, however, IOP measurements are problematic, cannot often be performed at the slit lamp, and sometimes require general anesthesia. Therefore, it is essential for an ophthalmologist who examines a pediatric patient to be aware of the different tonometers used in children, as well as the effects of central corneal thickness and anesthesia on IOP measurements. Goldmann applanation tonometry is the gold standard for IOP assessment. Most alternative tonometers tend to give higher IOP readings than the Goldmann applanation tonometer, and readings between different tonometers are often not interchangeable. Similar to Goldmann tonometry, many of these alternative tonometers are affected by central corneal thickness, with thicker corneas having artifactually high IOP readings and thinner corneas having artifactually lower IOP readings. Although various machines can be used to compensate for corneal factors (e.g., the dynamic contour tonometer and ocular response analyzer), it is important to be aware that certain ocular diseases can be associated with abnormal central corneal thickness values and that their IOP readings need to be interpreted accordingly. Because induction and anesthetics can affect IOP, office IOPs taken in awake patients are always the most accurate.