Portable tonometers: a clinical comparison of applanation and indentation devices

Optometric services to outpatient clinics, nursing homes and hospitals require portable equipment for ocular assessment. Of the various tonometric methods available, Goldmann applanation tonometry remains the standard. We present a clinical comparison of the hand-held version of Goldmann's instrument (Perkins tonometer) and the less expensive Schiotz tonometer. In a clinical comparison, we measured the intraocular pressure (IOP) of 51 inpatient and outpatient veterans (100 eyes) during routine examination. In each case the Perkins applanation tonometer was used first. This measurement was followed by IOP measurements using the Schiotz indentation tonometer with the 7.5 g and 5.5 g plunger loads. Plunger loads were alternated so that each was used, initially, 50% of the time. Good correlations, ranging from +.85 to +.68, were achieved between the applanation and indentation modes. Compact portability, lower cost and comparable reliability make the Schiotz tonometer a viable option for IOP screening.