A Comparison of the Corrected Intraocular Pressure Obtained by the Corvis ST and Reichert 7CR Tonometers in Glaucoma Patients

<div><p>The purpose of the study was to investigate the accuracy of two corrected intraocular pressure (IOP) measurements by Corvis Scheimpflug Technology (CST)-IOPpachy and by corneal-compensated IOP (IOPcc) using the Reichert 7CR (7CR) tonometers. We also investigated the effects of corneal anatomical and structural parameters on the IOP measurements. The participants included 90 primary open-angle glaucoma patients. We assessed the IOP measurements, obtained by the CST, 7CR, and Goldmann applanation tonometer (GAT), using a paired <i>t</i>-test with Bonferroni correction, Bland-Altman plots, and multiple regression analyses. The 7CR-IOPcc gave the highest value (15.5 ± 2.7 mmHg), followed by the 7CR-IOPg (13.7 ± 3.1 mmHg), GAT-IOP (13.6 ± 2.2 mmHg), CST-IOP (10.3 ± 2.6 mmHg), and CST-IOPpachy (9.7 ± 2.5 mmHg). The values of CST-IOPpachy were significantly lower than those obtained by the other IOP measurement methods (all, p < 0.01). The values of 7CR-IOPcc were significantly higher than those obtained by the other IOP measurement methods (all, p < 0.01). Bland-Altman plots showed a mean difference between the GAT-IOP and the other IOP measurements (CST-IOP, CST-IOPpachy, 7CR-IOPg, and 7CR-IOPcc), which were −3.20, −3.82, 0.14, and 2.00 mmHg, respectively. The widths of the 95% limits of agreement between all pairs of IOP measurements were greater than 3 mmHg. With the exception of the 7CR-IOPcc, all of the IOP variations were explained by regression coefficients involving gender, average corneal curvature, and central corneal thickness. The IOP values obtained by the GAT, CST, and 7CR were not interchangeable. Each new IOP measurement device that was corrected for ocular structure had its own limitations.</p></div

The results of univariate and multiple regression analyses: Factors independently associated with the intraocular pressure measurements (β, p, VIF).

<p>The results of univariate and multiple regression analyses: Factors independently associated with the intraocular pressure measurements (β, p, VIF).</p

Bland-Altman plots for inter-method differences.

<p>A, The differences between the CST-IOP and GAT-IOP. B, The difference between the CST-IOPpachy and GAT-IOP. C, The difference between the 7CR-IOPg and GAT-IOP. D, The difference between the 7CR-IOPcc and GAT-IOP. The mean values and 95% LOA are indicated by bold lines and solid lines, respectively. IOP, intraocular pressure; CST-IOP, IOP using the Corvis ST; CST-IOPpachy, corrected CST-IOP; GAT-IOP, IOP using the Goldmann applanation tonometer; 7CR-IOPg, Goldmann-correlated IOP using the 7CR tonometer; 7CR-IOPcc, corneal-compensated IOP using the 7CR tonometer; CI, confidence interval; LOA, limits of agreement.</p

Characteristics of primary open-angle glaucoma patients (n = 90).

<p>Characteristics of primary open-angle glaucoma patients (n = 90).</p

Product comparison.

<p>Product comparison.</p

Morphological Features and Important Parameters of Large Optic Discs for Diagnosing Glaucoma

<div><p>Purpose</p><p>To compare the optic disc parameters of glaucomatous eyes to those of non-glaucomatous eyes with large discs.</p><p>Methods</p><p>We studied 225 consecutive eyes with large optic discs (>2.82 mm2): 91 eyes with glaucoma and 134 eyes without glaucoma. An eye was diagnosed with glaucoma when visual field defects were detected by the Humphrey Field Analyzer. All of the Heidelberg Retina Tomograph II (HRT II) parameters were compared between the non-glaucomatous and glaucomatous eyes. A logistic regression analysis of the HRT II parameters was used to establish a new formula for diagnosing glaucoma, and the sensitivity and specificity of the Moorfields Regression Analysis (MRA) was compared to the findings made by our analyses.</p><p>Results</p><p>The mean disc area was 3.44±0.50 mm2 in the non-glaucomatous group and 3.40±0.52 mm2 in the glaucoma group. The cup area, cup volume, cup-to-disc area ratio, linear cup/disc ratio, mean cup depth, and the maximum cup depth were significantly larger in glaucomatous eyes than in the non-glaucomatous eyes. The rim area, rim volume, cup shape measurement, mean retinal nerve fiber layer (RNFL) thickness, and RFNL cross-sectional area were significantly smaller in glaucomatous eyes than in non-glaucomatous eyes. The cup-to-disc area ratio, the height variation contour (HVC), and the RNFL cross-sectional area were important parameters for diagnosing the early stage glaucoma, and the cup-to-disc area ratio and cup volume were useful for diagnosing advanced stage glaucoma in eyes with a large optic disc. The new formula had higher sensitivity and specificity for diagnosing glaucoma than MRA.</p><p>Conclusions</p><p>The cup-to-disc area ratio, HVC, RNFL cross-sectional area, and cup volume were important parameters for diagnosing glaucoma in eyes with a large optic disc. The important disc parameters to diagnose glaucoma depend on the stage of glaucoma in patients with large discs.</p></div

Demographics of the study subjects.

<p>The data are expressed as the means ± SD.</p><p>N: non-glaucomatous group</p><p>G: glaucomatous group</p><p>EG: early stage glaucoma group (MD <-5dB)</p><p>AG: advanced stage glaucoma group (MD ≥-5dB)</p><p>SE: spherical equivalent</p><p>MD: mean deviation</p><p>PSD: pattern standard deviation</p><p>* Difference between the normal group and all glaucoma cases</p><p>† Difference between the normal group and the early glaucoma group</p><p>‡ Difference between the normal group and the progressive/advanced glaucoma group</p><p>Demographics of the study subjects.</p

The ROC curves of the logistic regression analyses with the stepwise method in which glaucoma was the outcome variable among all subjects.

<p>The ROC curves of the logistic regression analyses with the stepwise method in which glaucoma was the outcome variable among all subjects.</p

The sensitivity and specificity of the MRA (Moorfield’s Regression Analysis) for all subjects (n = 225).

<p>tmp: temporal</p><p>nsl: nasal</p><p>sup: superior</p><p>inf: inferior</p><p>The sensitivity and specificity of the MRA (Moorfield’s Regression Analysis) for all subjects (n = 225).</p

The sensitivity and specificity of the MRA (Moorfield’s Regression Analysis) for the non-glaucomatous group and the early stage glaucoma group (n = 200).

<p>tmp: temporal</p><p>nsl: nasal</p><p>sup: superior</p><p>inf: inferior</p><p>The sensitivity and specificity of the MRA (Moorfield’s Regression Analysis) for the non-glaucomatous group and the early stage glaucoma group (n = 200).</p