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Yukinori Harada - One of the best experts on this subject based on the ideXlab platform.

  • IOP measured by dynamic contour tonometry correlates with IOP measured by goldmann applanation tonometry and non-contact tonometry in Japanese individuals
    Journal of Glaucoma, 2012
    Co-Authors: Ken Ito, Toshiaki Kubota, Akihiko Tawara, Yukinori Harada
    Abstract:

    PURPOSE: The purpose of this study was threefold. We sought to compare the intraocular pressure (IOP) measured by dynamic contour tonometry (DCT) with that measured by Goldmann applanation tonometry (GAT) and noncontact tonometry (NCT). We also examined the influence of central corneal thickness (CCT) and corneal curvature radius (CCR) on the IOP measurements. Last, we investigated the factors that could affect the ocular pulse amplitude (OPA) measurements.\n\nMETHODS: Seventy-four patients with no history of intraocular surgery were enrolled in this study. We measured IOP by DCT, GAT, and NCT, and the CCT, CCR, and axial length (AL) in the right eye of each patient. We also measured OPA by DCT. We subsequently analyzed the correlation of IOP measurements between GAT and DCT and between NCT and DCT. We also examined the influence of CCT, CCR, and AL on IOP readings by the 3 tonometers. In addition, we investigated the factors that could affect the OPA measurements.\n\nRESULTS: The mean IOP measured by DCT was 2.8 mm Hg higher than that by GAT and 3.2 mm Hg higher than that by NCT. This difference was greater with thinner CCT in the lower IOP group than in the higher IOP group. IOP measurements by both GAT and NCT significantly correlated with CCT; however, IOP measurement by DCT did not correlate with CCT. No significant correlations were shown between the IOP measured by each of the 3 tonometers and either CCR or AL. OPA measurements positively correlated with age, IOP measurement by DCT, and pulse pressure.\n\nCONCLUSIONS: IOP measured by DCT correlates with IOP measured by GAT or NCT with a roughly 3.0 mm Hg higher value, and these differences were greater in the patients with a thinner CCT. IOP measurements by both GAT and NCT significantly correlated with CCT; however, IOP measurement by DCT did not correlate with CCT. Our findings also indicate that OPA measured using DCT shows a positive correlation with patient age, IOP measurement by DCT, and pulse pressure.

Dexin Zhang - One of the best experts on this subject based on the ideXlab platform.

  • DCT based iris recognition
    IEEE Transactions on Pattern Analysis and Machine Intelligence, 2007
    Co-Authors: Donald M Monro, S Rakshit, Dexin Zhang
    Abstract:

    This paper presents a novel iris coding method based on differences of discrete cosine transform (DCT) coefficients of overlapped angular patches from normalized iris images. The feature extraction capabilities of the DCT are optimized on the two largest publicly available iris image data sets, 2,156 images of 308 eyes from the CASIA database and 2,955 images of 150 eyes from the Bath database. On this data, we achieve 100 percent correct recognition rate (CRR) and perfect receiver-operating characteristic (ROC) curves with no registered false accepts or rejects. Individual feature bit and patch position parameters are optimized for matching through a product-of-sum approach to Hamming distance calculation. For verification, a variable threshold is applied to the distance metric and the false acceptance rate (FAR) and false rejection rate (FRR) are recorded. A new worst-case metric is proposed for predicting practical system performance in the absence of matching failures, and the worst case theoretical equal error rate (EER) is predicted to be as low as 2.59 times 10-1 available data sets

Ken Ito - One of the best experts on this subject based on the ideXlab platform.

  • IOP measured by dynamic contour tonometry correlates with IOP measured by goldmann applanation tonometry and non-contact tonometry in Japanese individuals
    Journal of Glaucoma, 2012
    Co-Authors: Ken Ito, Toshiaki Kubota, Akihiko Tawara, Yukinori Harada
    Abstract:

    PURPOSE: The purpose of this study was threefold. We sought to compare the intraocular pressure (IOP) measured by dynamic contour tonometry (DCT) with that measured by Goldmann applanation tonometry (GAT) and noncontact tonometry (NCT). We also examined the influence of central corneal thickness (CCT) and corneal curvature radius (CCR) on the IOP measurements. Last, we investigated the factors that could affect the ocular pulse amplitude (OPA) measurements.\n\nMETHODS: Seventy-four patients with no history of intraocular surgery were enrolled in this study. We measured IOP by DCT, GAT, and NCT, and the CCT, CCR, and axial length (AL) in the right eye of each patient. We also measured OPA by DCT. We subsequently analyzed the correlation of IOP measurements between GAT and DCT and between NCT and DCT. We also examined the influence of CCT, CCR, and AL on IOP readings by the 3 tonometers. In addition, we investigated the factors that could affect the OPA measurements.\n\nRESULTS: The mean IOP measured by DCT was 2.8 mm Hg higher than that by GAT and 3.2 mm Hg higher than that by NCT. This difference was greater with thinner CCT in the lower IOP group than in the higher IOP group. IOP measurements by both GAT and NCT significantly correlated with CCT; however, IOP measurement by DCT did not correlate with CCT. No significant correlations were shown between the IOP measured by each of the 3 tonometers and either CCR or AL. OPA measurements positively correlated with age, IOP measurement by DCT, and pulse pressure.\n\nCONCLUSIONS: IOP measured by DCT correlates with IOP measured by GAT or NCT with a roughly 3.0 mm Hg higher value, and these differences were greater in the patients with a thinner CCT. IOP measurements by both GAT and NCT significantly correlated with CCT; however, IOP measurement by DCT did not correlate with CCT. Our findings also indicate that OPA measured using DCT shows a positive correlation with patient age, IOP measurement by DCT, and pulse pressure.

Gerassimos Lascaratos; David F Garway-heath; Richard A Russell; David Paul Crabb; Haogang Zhu; Corne Ukgts - One of the best experts on this subject based on the ideXlab platform.

  • Intraocular pressure (IOP) measured with the Ocular Response Analyzer is a better predictor of glaucoma progression than Goldmann IOP in the United Kingdom Glaucoma Treatment Study (UKGTS)
    Investigative Ophthalmology & Visual Science, 2014
    Co-Authors: Gerassimos Lascaratos; David F Garway-heath; Richard A Russell; David Paul Crabb; Haogang Zhu; Corne Ukgts
    Abstract:

    Purpose: Intraocular pressure (IOP) and central corneal thickness (CCT) are important risk factors for glaucoma progression. However, it is uncertain whether CCT risk is independent or mediated through IOP measurement error. The Ocular Response Analyzer (ORA) and Dynamic Contour Tonometer (DCT) make IOP measurements less affected by corneal biomechanics than the Goldmann applanation tonometer (GAT). Our hypothesis was that the correlation between the rate of visual field (VF) loss and ORA IOP and DCT IOP is stronger than with GAT IOP. Methods: 516 previously untreated open angle glaucoma patients were monitored over 2 years in the United Kingdom Glaucoma Treatment Study with VF testing, and tonometry with the GAT, DCT and ORA at 11 visits. The eye with the most negative baseline mean deviation (MD) was selected and only eyes with VFs over at least 5 visits were included. Pearson’s correlation coefficient (R) was used to measure the strength of the relationship between median follow-up IOP [GAT, DCT, corneal compensated IOP (IOPcc) and Goldmann correlated IOP (IOPg)] and MD slope. IOP models, with CCT, corneal hysteresis (CH), corneal resistance factor (CRF) and axial length (AL) included as covariates, were compared using the Akaike Information Criterion (AIC) and Akaike weights (AWs). Data analysis was performed with the statistical software R. Results: 342 eyes of 342 patients were included. Pearson’s R of the MD slope against median GAT IOP, DCT IOP, IOPcc and IOPg was 0.263, 0.230, 0.294 and 0.244, respectively (P

Donald M Monro - One of the best experts on this subject based on the ideXlab platform.

  • DCT based iris recognition
    IEEE Transactions on Pattern Analysis and Machine Intelligence, 2007
    Co-Authors: Donald M Monro, S Rakshit, Dexin Zhang
    Abstract:

    This paper presents a novel iris coding method based on differences of discrete cosine transform (DCT) coefficients of overlapped angular patches from normalized iris images. The feature extraction capabilities of the DCT are optimized on the two largest publicly available iris image data sets, 2,156 images of 308 eyes from the CASIA database and 2,955 images of 150 eyes from the Bath database. On this data, we achieve 100 percent correct recognition rate (CRR) and perfect receiver-operating characteristic (ROC) curves with no registered false accepts or rejects. Individual feature bit and patch position parameters are optimized for matching through a product-of-sum approach to Hamming distance calculation. For verification, a variable threshold is applied to the distance metric and the false acceptance rate (FAR) and false rejection rate (FRR) are recorded. A new worst-case metric is proposed for predicting practical system performance in the absence of matching failures, and the worst case theoretical equal error rate (EER) is predicted to be as low as 2.59 times 10-1 available data sets