Comparative evaluation of intraocular pressure with an air-puff tonometer versus a Goldmann applanation tonometer

Abstract

PurposeTonometry, or measurement of intraocular pressure (IOP), is one of the most important examination procedures in ophthalmic clinics, and IOP is an important parameter in the diagnosis of glaucoma. Because there are numerous types of tonometer available, it is important to evaluate the differences in readings between different tonometers. Goldmann applanation tonometers (GATs) and noncontact air-puff tonometers (APTs) are largely available in ophthalmic clinics. The purpose of this study was to evaluate the role of AP tonometer by comparing the measurements of IOP made using this device with those made using a GAT.Patients and methodsThis study involved 196 eyes from 98 study participants, all of whom were patients attending an ophthalmic outpatient clinic. Each patient’s IOP was measured using both Goldmann applanation tonometry and AP tonometry, and the difference in readings between the two methods was calculated.ResultsThe mean IOP as measured by GAT was 13.06 ± 4.774 mmHg, while that as measured by AP tonometer was 15.91 ± 6.955 mmHg. The mean difference between the two methods of measurement was 2.72 ± 2.34 mmHg. The readings obtained by AP tonometer were higher than those obtained by GAT in 74% of patients, and this difference was most obvious when the GAT measurement of IOP exceeded 24 mmHg. No statistically significant variation in IOP was noted between the devices when the patients’ age, sex, and laterality (right and left eyes) were considered.ConclusionThere is a significant difference in the measurement of IOP between GATs and AP tonometers. Goldmann applanation tonometry remains the most suitable and reliable method for measuring IOP. Because measurements of IOP by AP tonometer are usually higher than those obtained by GAT regardless of the patient’s age, sex, or laterality of eyes, AP tonometry is a suitable method for community or mass screenings of IOP.

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“…It is also worth noting that the average age of the China study population was about 14 years younger than that of the US study population, and younger age has also been associated with steroid-induced IOP elevations.- 20,25 Furthermore, different techniques were used to measure IOP in the US (applanation tonometry) and China (non-contact tonometry) studies. Non-contact tonometry has been shown to overestimate IOP relative to applanation tonometry in some studies, 26,27 while others have reported similar results between the two methods. 28,29 A number of studies have noted better intra-and interoperative reproducibility of IOP measurements with Goldman applanation tonometry and dynamic contour tonometry (DCT) compared with non-contact methods.…”

Comparison of three methods of tonometry in normal subjects: Goldmann applanation tonometer, non-contact airpuff tonometer, and Tono-Pen XL

“…However, other studies found contrasting results 23,24. Farhood23 showed that NCT and GAT were not well correlated, and NCT measurements gave higher IOP results regardless of the patient’s age or sex. In particular, when the GAT measurement exceeded 24 mmHg, the difference in readings between the two instruments increased.…”

“…In another study, Tonnu et al17 compared NCT, TPXL, and GAT and reported that all three devices showed homologous results 17. However, other studies found contrasting results 23,24. Farhood23 showed that NCT and GAT were not well correlated, and NCT measurements gave higher IOP results regardless of the patient’s age or sex.…”

Air-Puff Tonometry in population research – a comparison with Goldmann tonometer in individuals with suspected ocular hypertension

“…A study evaluating the IOP ranging from 6 to 40 mmHg with different tonometers found variable concordances according to the blood pressure levels, with overestimated or underestimated values (14) . According to other authors, the difference between the methods is more important when the IOP exceeds 24 mmHg with TG, and the matching between the methods is seen especially when IOP values are below 20 mmHg (16) . The results of the present study are in line with the literature findings, which show that the values obtained with TA are higher than those obtained with TG.…”

“…TAs must be considered for their efficiency in the detection of elevated IOP indicating glaucoma. There are many positive points in favor of the use of TAs in populational studies, such as a simpler use, faster service, needless to use anesthetic eyedrops and fluorescein, reduced contamination risk by contact of secretions from different patients, lack of corneal abrasion, more comfort and possibility of use by assistants of ophthalmologists (16) . Although the confirmation of the measure with TG is necessary when the IOP exceeds the limits deemed normal values, TA is very useful as a screening method.…”