Validity and limitations of the Nidek NT‐4000 non‐contact tonometer: a clinical study

Abstract

Using Goldmann applanation tonometry (GAT) as a gold standard, we evaluated the accuracy of Nidek NT-4000 pneumotonometry (NPT) in adults without corneal disease. Bland and Altman analysis of serial intra-ocular pressures (IOPs) measured with NPT and GAT in 10 healthy subjects revealed that the repeatability coefficients for the two methods were similar. NPT, GAT and ultrasonic pachymetry were then performed in 100 patients. Bland and Altman analysis showed that NPT yielded significantly higher readings than GAT [mean biases for right and left eye measurements were 1.37 mmHg (95% limits of agreement: -3.02-5.76) and 1.17 mmHg (95% limits of agreement: -2.76-5.11) respectively] and was more affected by corneal thickness variations. For detection of IOPs > or =21 mmHg, NPT displayed very high sensitivity (0.90) and good specificity (0.95). NPT may be useful in screening and clinical settings but borderline-high IOP readings should be confirmed with GAT.

The influence of soft contact lenses on the intraocular pressure measurement

“…Several studies compared the reproducibility and reliability of IOP measurements obtained with NCT, DCT, and GAT. [21][22][23][24] In most of these studies, similar reproducibility and reliability were demonstrated with all three devices. In this study, however, the results indicated better reproducibility of measurements for NCT, DCT, and GAT without a contact lens than with one.…”

Correlation Between Corneal and Scleral Pneumatonometry: An Alternative Method for Intraocular Pressure Measurement

“…A few techniques, including limbal pneumatonometry 5 and noncontact tonometry, 4 have been suggested as reliable alternatives for IOP measurements in diseased corneas. To our knowledge, we are unaware of any reports investigating these techniques in eyes implanted with keratoprostheses.…”

“…Various alternatives, including tactile estimation, have been suggested, but these require the use of special implants and/or measuring techniques that are not practical in the office setting. [1][2][3][4][5] Additionally, various disease states, including acromegaly, corneal edema, and keratoconus, produce surface and/or thickness irregularities that undermine the accuracy of IOP measurements. 6 Presently, corneal pneumatonometry is an acceptable alternative when dealing with diseased or irregular corneas, where mire distortion precludes the accuracy of Goldmann applanation tonometry (GAT).…”

Corneal structure and biomechanics: impact on the diagnosis and management of glaucoma

“…An optical detector measures the change in light reflected from the corneal surface and correlates the change to IOP [48 ]. Several studies have found that NCT is significantly affected by CCT.…”