Goldmann Applanation Tonometry: Using a Red-Free Filter for Mass Screening

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial 3.0 License (CC BY-NC 3.0), which allows users to read, copy, distribute and make derivative works for non-commercial purposes from the material, as long as the author of the original work is cited properly. Goldmann applanation tonometry is the gold standard medical instrument for the measurement of intraocular pressure (IOP) for a long time (1, 2). Fluorescein staining (either using a fluorescein-impregnated paper strip or a fluorescein solution) is often conducted prior to IOP measurement. However, following the application of fluorescein, patients often experience a stinging sensation, eyelid discoloration, mucus discharge, or a combination of these side effects. To avoid these side effects, and to thereby improve patient comfort, several researchers have suggested that IOP measurement should be conducted without fluorescein. However, there is no consensus on this proposal, and some of the researchers have proposed using a reduced quantity of fluorescein, while others have suggested completely eliminating it (3,4,6). Au et al. measured the IOP of 30 subjects using Goldmann applanation tonometry with a small quantity of fluorescein, and they found that this technique was an effective and precise method for measuring IOP prior to fitting soft contact lenses (3). In addition, a recent cross-sectional study by Ghoneim et al. measured the IOP of 250 patients, first with fluorescein (with cobalt blue light) and then without fluorescein (with red-free light). There was no significant difference in the measured IOP between the two measurement methods. The mean IOP using the technique without fluorescein was 15.23 ± 3.3 mmHg, and that associated with the use of fluorescein was 12.8215.78 ± 2.43.7 mmHg (4). The authors concluded that IOP measurement using Goldmann applanation tonometry without fluorescein and with a red-free filter resulted in accurate IOP measurements (4). In contrast, a 1981 study by Bright et al. of 100 patients found that the mean IOP measured without fluorescein