Measurement of intraocular pressure using the NT-4000: a new non-contact tonometer equipped with pulse synchronous measurement function.

PURPOSE: NT-4000 (Nidek Co. Ltd., Gamagori, Japan) is a new non-contact tonometer (NCT) equipped with pulse synchronous measurement function that can measure intraocular pressure (IOP) synchronized with the ocular pulse. The purpose of this study was to evaluate the usefulness of NT-4000 in normal subjects and in patients with glaucoma and ocular hypertension. METHODS: This study included 175 eyes of 175 subjects. Firstly, the IOP was measured using NT-4000 without the pulse synchronous measurement function (NTn). Secondly, the IOP at peak, middle, and trough phases of the pulse signal were measured using NT-4000 with the pulse synchronous measurement function (NTp, NTm, NTt, respectively). Additionally, the IOP was measured with Goldmann applanation tonometer (GT). The coefficient of variation (CV) of three readings in the NCT measurements was used to evaluate the intra-session reproducibility. Statistical comparisons were performed using Wilcoxon signed rank test and one-way analysis of variance with Scheffe's test. Linear regression analysis was used to calculate correlation coefficients. P values less than 0.05 were accepted as statistically significant. RESULTS: The CV of NTn, NTp, NTm, and NTt were 6.4%, 5.5%, 4.9%, and 5.2%, respectively. The CV of NTp, NTm, and NTt were significantly smaller than that of NTn (P = 0.007, P < 0.001, P < 0.001, respectively). NTp was significantly higher than NTt (P = 0.038). GT was significantly correlated with NTn, NTp, NTm, and NTt (r = 0.898, P < 0.001; r = 0.912, P < 0.001; r = 0.908, P < 0.001; r = 0.900, P < 0.001, respectively). CONCLUSION: NT-4000 can detect the fluctuation of IOP associated with the ocular pulse.

Optic disc topography as measured by confocal scanning laser ophthalmoscopy and visual field loss in Japanese patients with primary open-angle or normal-tension glaucoma.

PURPOSE: To determine whether differences in the optic disc topography and those in the relation between the optic disc topography and visual field indices exist between Japanese patients with primary open-angle glaucoma (POAG) and normal-tension glaucoma (NTG). METHODS: The study included consecutive Japanese patients with POAG (n = 60) or NTG (n = 60). Using the Heidelberg Retina Tomograph (HRT), we measured disc area, cup area, cup-to-disc area ratio, rim area, cup volume, rim volume, cup shape measure, and height variation contour. Each HRT parameter was measured in the total optic disc and in its four 90 degree quadrants (superior, temporal, inferior, and nasal). The mean deviation for the entire field and the sum of the total deviation values corresponding to each optic disc quadrant were calculated using the Humphrey full-threshold 30-2 program. RESULTS: No significant differences were found between the POAG and NTG groups for any HRT parameter either globally or regionally. There were no significant differences between the two groups in the correlation coefficients between any HRT parameter and the corresponding visual field indices either globally or regionally. CONCLUSION: No significant differences were apparent between Japanese patients with POAG and NTG both in the optic disc parameters as measured by HRT and in the degree of correlation between HRT parameter and the corresponding visual field indices.

Relationship between indices of Humphrey perimetry and Frequency Doubling Technology Perimetry in glaucoma.

PURPOSE: To study whether the correlation between indices of Humphrey perimetry and Frequency Doubling Technology (FDT) perimetry differs in the early and later stages of glaucoma. METHODS: This study included 200 eyes of 200 patients with primary open-angle glaucoma or normal-tension glaucoma. The eyes were classified into the early and later stages by the median value (-4.51 dB) (Classification 1; n = 100 and 100, respectively) or the average value of the maximum and minimum values (-11.90 dB) (Classification 2; n = 165 and 35, respectively) of mean deviation (MD) obtained from a set of measurements with the Humphrey Full-Threshold 30-2 program in all eyes. The correlation between MD (H-MD) or pattern standard deviation (PSD) (H-PSD), as obtained from another set of measurements with the Humphrey Full-Threshold 30-2 program, and MD (F-MD) or PSD (F-PSD), as calculated by the Full-Threshold N-30 program of FDT perimetry, were evaluated using linear regression analysis. RESULTS: Overall, H-MD and H-PSD significantly correlated with F-MD (r = 0.713; P < 0.001) and F-PSD (r = 0.731; P < 0.001), respectively. In each of Classifications 1 and 2, H-MD and H-PSD significantly correlated with F-MD and F-PSD, respectively, both in the early and later stages. However, in each classification, the correlation between H-MD and F-MD differed significantly between the two stages (Classification 1; P < 0.001; Classification 2, P = 0.003), while the correlation between H-PSD and F-PSD did not differ significantly between the two stages. CONCLUSION: The degree of correlation between H-MD and F-MD differed between the early and later stages of glaucoma.