José Alberto Diaz-Rey

Comparison of the ICare® rebound tonometer with the Goldmann tonometer in a normal population

The aim of this study was to evaluate the accuracy of measurement of intraocular pressure (IOP) using a new induction/impact rebound tonometer (ICare®) in comparison with the Goldmann applanation tonometer (AT).

Clinical performance of the Reichert AT550: a new non-contact tonometer

The aim of the present study was to assess the level of accuracy for measurements of intra‐ocular pressure (IOP) obtained with a new non‐contact tonometer (NCT) the Reichert AT550®. Measurements were compared against those obtained with the Reichert Xpert Plus, Goldmann applanation tonometer and Perkins tonometer. Thirty‐five university students were assessed with the four tonometers in a randomised order, with non‐contact tonometry performed first. Each of the four measurement devices had its own trained clinical observer. Plots of differences of IOP as a function of the mean for each pair of instruments were obtained. No statistically significant differences were found when comparing the AT550® NCT with contact applanation tonometry (AT) (p > 0.05), displaying the closest level of agreement (as represented by the lowest mean difference and the narrowest confidence interval) with the Goldmann tonometer (limits of agreement, 0.12 ± 2.17). In conclusion, readings of IOP with the AT550® NCT are clinically comparable with those obtained with Goldmann tonometry in a population with IOP within the normal range.

Clinical performance of non-contact tonometry by Reichert AT550 in glaucomatous patients.

Measuring intraocular pressure (IOP) by non‐contact tonometry (NCT) has been demonstrated to be a valid and reliable technique to be used in primary eye care; it is easier to use, it does not transmit infectious diseases, and it is not necessary to use anaesthetic or staining eye drops. Recently, a new NCT device has showed an excellent level of agreement with Goldmann tonometry, but there are no records of its performance in glaucomatous eyes. To rectify this, IOP was measured in twenty‐two patients (44 eyes) receiving medical treatment to control elevated IOP, with AT550® and Goldmann tonometry. Mean values of IOP were 18.98 ± 2.77 and 19.08 ± 3.02 mmHg using Goldmann and AT550®, respectively. Plots of differences against means displayed good agreement (mean difference ± limits of agreement, −0.09 ± 3.30); this value was not significantly different from zero (t‐test for dependent samples, p = 0.709). In conclusion, IOP values as measured with the AT550® NCT are clinically comparable with those obtained with Goldmann tonometry in glaucomatous patients. This validates this NCT not only for screening of IOP but to follow‐up glaucomatous patients with a rapid, non‐invasive method.

Central corneal thickness and anterior chamber depth measurement by Sirius® Scheimpflug tomography and ultrasound

Background The purpose of this study was to compare the accuracy of the new Sirius® Scheimpflug anterior segment examination device for measurement of central corneal thickness (CCT) and anterior chamber depth (ACD) with that of CCT measurements obtained by ultrasound pachymetry and ACD measurements obtained by ultrasound biometry, respectively. Methods CCT and ACD was measured in 50 right eyes from 50 healthy subjects using a Sirius Scheimpflug camera, SP100 ultrasound pachymetry, and US800 ultrasound biometry. Results CCT measured with the Sirius was 546 ± 39 μm and 541 ± 35 μm with SP100 ultrasound pachymetry (P = 0.003). The difference was statistically significant (mean difference 4.68 ± 10.5 μm; limits of agreement −15.8 to 25.20 μm). ACD measured with the Sirius was 2.96 ± 0.3 mm compared with 3.36 ± 0.29 mm using US800 ultrasound biometry (P < 0.001). The difference was statistically significant (mean difference −0.40 ± 0.16 mm; limits of agreement −0.72 to 0.07 mm). When the ACD values obtained using ultrasound biometry were corrected according to the values for CCT measured by ultrasound, the agreement increased significantly between both technologies for ACD measurements (mean difference 0.15 ± 0.16 mm; limits of agreement −0.16 to 0.45 mm). Conclusion CCT and ACD measured by Sirius and ultrasound methods showing good agreement between repeated measurements obtained in the same subjects (repeatability) with either instrument. However, CCT and ACD values, even after correcting ultrasound ACD by subtracting the CCT value obtained with either technology should not be used interchangeably.

A comparison of the NCT Reichert R7 with Goldmann applanation tonometry and the Reichert ocular response analyzer

Citation information: Jorge J, González‐Méijome JM, Queirós A, Fernandes P & Diaz‐Rey JA. A comparison of the NCT Reichert R7 with Goldmann applanation tonometry and the Reichert ocular response analyzer. Ophthalmic Physiol Opt 2011, 31, 174–179. doi: 10.1111/j.1475‐1313.2010.00817.x

Corneal thickness mapping by topographical ultrasonic pachometry

Abstract Ultrasonic measurements of corneal thickness (CT) more than 25 points from a 6-mm diameter area of the central cornea were used to create computerized CT maps. Two subjects were evaluated in different sessions by topographical ultrasonic pachometry. The thickness values were stored as a two-dimensional array z(x,y), whose indices refer to positional coordinates x (in the nasal–temporal direction) and y (in the superior–inferior direction). Pachometric maps were then constructed by plotting thickness values against horizontal and vertical (x,y) position coordinates. Assisted computer interpolation between data points provides color-coded continuous pachometric maps. Data were processed and analyzed separately and an average map was also obtained for each subject. Goodness of fit for the average maps measured by coefficient of determination (r 2 ) was very high in both examples (r 2 = 0.98 and r 2 = 0.99). Fitting standard error was 5.42 μm and 4.17 μm, respectively. Also, points not measured in the ultrasonic evaluation could be automatically predicted from the fitted model. The technique described provides an affordable and reliable method for thickness mapping of full corneal tissue, enabling accurate anatomical evaluation of the changes induced in the cornea by refractive surgery procedures, contact lenses, or disease.