Comparison of Central Corneal Thickness Measurements between Noncontact Specular Microscopy and Ultrasound Pachymetry

PURPOSE: We compared and analyzed central corneal thickness (CCT) measurements according to the corneal thickness obtained with noncontact specular microscopy (NCSM) and ultrasound pachymetry (USP). METHODS: CCT was measured in the order of NCSM and USP by a single optometrist in 120 eyes of 120 healthy subjects. The measurements were compared between the devices and the measurement agreements and correlations between the devices were analyzed. To determine if the measurements differed depending on the thickness of the cornea, the patients were divided into three tertile groups from the thinnest patient by CCT measurement using USP, and then the differences in CCT measured by the two devices were analyzed. RESULTS: The CCT measurements using NCSM and USP were 548.25 ± 4.64 µm and 533.09 ± 35.96 µm, respectively. NCSM measurements were found to be thicker, showing statistically significant differences between the measurements (p < 0.001). The two examinations showed a high degree of correlation (r = 0.878; p < 0.01). In the three groups, the differences in CCT measurements between NCSM and USP were 12.93 ± 21.88 µm, 16.85 ± 15.89 µm, and 15.70 ± 20.46 µm, respectively, but the differences between the three groups were not statistically significant (p = 0.655). CONCLUSIONS: Our results show that although the differences in CCT measurements using NCSM and USP were consistent regardless of the corneal thickness, the CCT measurements by NCSM and USP were highly correlated.

Comparison of the thinnest corneal thickness measured by Sirius, Oculyzer, AS-OCT and A-mode ultrasonography in myopic patients / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM:To compare the difference, correlation and consistency of the thinnest corneal thickness(TCT)in myopic patients among Sirius, Oculyzer, anterior segment optical coherence tomography(AS-OCT)and A-mode ultrasound pachymetry, in order to provide a reference for clinical applications.<p>METHODS: TCT was measured in 81 patients(162 eyes)treated between March and April, 2016 using Sirius, Oculyzer, AS-OCT and A-mode ultrasound pachymetry before femtosecond LASIK, and then the values were statistically analyzed.<p>RESULTS: TCT measured by A-mode ultrasound pachymetry, Sirius, Oculyzerand AS-OCT were respectively(537.91±24.12)μm,(538.12±22.64)μm,(538.20±23.74)μm,(527.04±23.11)μm(<i>P</i><0.01). There was a significant difference in TCT measurements among the four measurements. The results of AS-OCT were significantly smaller than those of the other three methods. There was no statistical difference among A-mode ultrasound pachymetry, Sirius and Oculyzer.Pearson correlation coefficient of measured value by the four measurements were more than 0.9(<i>r</i>=0.920, 0.914, 0.951, 0.908, 0.929, 0.919, <i>P</i><0.001), which means there were highly correlation between each other. The 95% <i>CI</i> of the consistency interval of A-mode ultrasound pachymetry and Sirius, A-mode ultrasound pachymetry and Oculyzer, A-mode ultrasound pachymetry and AS-OCT were(-18.77-18.33)μm,(-19.79-19.19)μm,(-3.79-25.53)μm, respectively. The Bland-Altman Plots demonstrates relatively good consistency between A-mode ultrasound pachymetry and the other three methods.<p>CONCLUSION:The TCT measured by AS-OCT were thinner than that measured by A-mode ultrasound pachymetry. There were a high correlation and consistency of the thinnest corneal thickness in myopic patients among Sirius, Oculyzer, AS-OCT and A-mode ultrasound pachymetry. The TCT measured by the four measurements can be referenced but not replaced since the 95% of the consistency intervals were wide.

Comparison of Central Corneal Thickness Measured by Swept-source Optical Coherence Tomography and Ultrasound Pachymetry

PURPOSE: To analyze and compare ultrasound pachymetry (USP) with a more recently adopted device, the intra ocular lens (IOL) master 700, which are both used to measure central corneal thickness. METHODS: The central corneal thickness was measured in 24 eyes of 12 glaucoma patients and in 83 eyes of 42 normal patients. First, the IOL master 700 was used to measure the central corneal thickness, followed by measurements taken using USP later. The results were analyzed using a paired t-test. We analyzed the agreement and the correlations between the two test devices by using Bland-Altman plots and the Pearson correlation test. To evaluate the reproducibility, measurements with the IOL master 700 were taken twice for a few normal patients within a small time interval. RESULTS: Via the IOL master 700, the thickness of the central cornea showed a high reproducibility and repeatability, demonstrating 2.7 ± 1.7 µm for the test-retest variability, 6.78% for the coefficient of variation, and 0.997 for the intraclass correlation value. The mean measurements using USP and the IOL master 700 are 554.4 ± 37.4 µm and 551.1 ± 37.1 µm, respectively, showing that the IOL master 700 measured significantly smaller values than USP with a p-value < 0.001. The deviations between the two methods are scattered throughout the 95% confidence interval. According to the Pearson correlation test, the measured values of the two test devices were found to have a highly positive correlation (r = 0.977, p < 0.0001). CONCLUSIONS: This study demonstrated that the central corneal thickness (CCT) measured via the IOL master was significantly thinner than that of USP, and the two test devices had a high correlation and good agreement. The CCT value measured via the IOL master 700 also exhibited high reproducibility.

Corneal Thickness Measurements Using 2 Kinds of Spectral Domain Optical Coherence Tomography, Pentacam, Ultrasound Pachymetry

PURPOSE: To compare the measurements of central corneal thickness (CCT) obtained using two kinds of spectral domain optical coherence tomography (OCT), Pentacam®, and ultrasound pachymetry (USP). METHODS: CCT was measured by Cirrus OCT®, Spectralis OCT®, Pentacam®, and USP in 32 eyes from 32 subjects without ocular disease of the anterior segment. RESULTS: The average CCT measurements using Cirrus OCT®, Spectralis OCT®, Pentacam®, and USP were 549.2 ± 28.7 µm, 545.2 ± 25.4 µm, 554.0 ± 27.8 µm, and 548.4 ± 27.9 µm respectively. The measurements were significantly highly correlated with each other (Pearson's correlation coefficient r > 0.9, all p-values < 0.001), but were significantly different (p < 0.001). The CCT 95% limits of agreement between Cirrus OCT® and Spectralis OCT®, Cirrus OCT® and Pentacam®, Cirrus OCT® and USP, Spectralis OCT® and Pentacam®, and Spectralis OCT® and USP were 27.70 µm, 26.1 µm, 26.97 µm, 22.91 µm, 35.59 µm, and 32.15 µm, respectively. CONCLUSIONS: The CCT values measured using the four devices were highly correlated with each other, but the measurement using Pentacam® was significantly thicker than that using USP. The measurements of the two kinds of spectral domain OCT were similar to those using USP. Therefore, these differences should be considered in clinical use, and measurements cannot be considered interchangeable.

Utility of the Swept Source Optical Coherence Tomography for Measurements of Central Corneal Thickness

PURPOSE: To evaluate the efficacy of swept source optical coherence tomography (SS-OCT) by comparing the measurement of central corneal thickness (CCT) to the measurement obtained using Orbscan II, anterior segment optical coherence tomography (AS-OCT) and ultrasound pachymetry. METHODS: One examiner measured the CCT in 65 eyes of 65 healthy subjects using Orbscan II, AS-OCT, SS-OCT and ultrasound pachymetry. The mean values and correlations were analyzed. RESULTS: The average CCT measurements obtained using Orbscan II, AS-OCT, SS-OCT and ultrasound pachymetry were 534.83 ± 38.46, 517.80 ± 32.48, 528.22 ± 33.71 and 528.02 ± 34.90 µm, respectively. A significant linear correlation was observed among Orbscan II, AS-OCT, SS-OCT and ultrasound pachymetry (r > 0.894, p < 0.001). There was no significant difference between the SS-OCT and ultrasound pachymetry (p = 0.782). CONCLUSIONS: The results of the 4 methods were significantly correlated and the SS-OCT reached a high level of agreement when CCT was determined using ultrasound pachymetry. The CCT measurements using SS-OCT is a better alternative for ultrasound pachymetry than Orbscan II and AS-OCT.

Comparability and repeatability of pachymetry in keratoconus using four noncontact techniques.

Purpose: To compare and determine the repeatability of central corneal thickness (CCT) measurements using four noncontact pachymetry instruments in eyes with keratoconus. Materials and Methods: The CCT of consecutive patients with keratoconus was measured during a single visit using the swept source optical coherence tomography (SS‑OCT, Casia SS‑1000°CT, Tomey, Nagoya, Japan), a rotating Scheimpflug camera system (Pentacam, Oculus Optikgerate GmbH, Wetzlar, Germany), scanning slit topographer (Orbscan IIz topography, Baush and Lomb Surgical Inc., San Dimas, CA, USA), and a hand‑held spectral domain OCT (HHSD‑OCT, Bioptigen Inc., Durham, North Carolina, USA). Test‑retest variability, correlation between measurements and interdevice agreement were analyzed. Results: Fifty eyes of 25 participants were analyzed in this study. All measurement methods correlated well with each other (r > 0.9, P < 0.001). Mean ± standard deviation CCT measured by HHSD‑OCT, Orbscan IIz, SS‑OCT, and Pentacam was 462 ± 41 μm, 458 ± 41 μm, 454 ± 40 μm, and 447 ± 42 μm, respectively. While the HHSD‑OCT over‑estimated the CCT (P < 0.001), there was a good correlation between the measurements obtained from the other three devices. However, the numerical difference was high and this trend was seen in all the paired comparisons. Conclusions: Though the measurements by different devices correlated well, the numerical agreement may be inadequate for their interchangeable use in clinical practice.

Comparison of different methods for the measurement of central and paracentral corneal thickness in post-LASIK eyes / 中华实验眼科杂志

Background Accurate measurement of corneal thickness is very important during the pre-and post-operative management of corneal surgical procedures,especially laser-assisted in-situ keratomileusis (LASIK),which is the most popular approach to the correction of refractive errors currently.This may be particularly important for the patients who have undergone previous laser refractive surgery with suboptimal outcomes and are being considered for an enhancement procedure.Objective This study was to compare the measuring outcomes of corneal thickness by slit-scanning pachymetry,non-contact specular microscope,anterior segment optical coherence tomography (AS-OCT)and ultrasound pachymetry,with a focus on central and midperipheral (from the central 3.0 mm) region of cornea in post-LASIK eyes.Methods Sixty-four right eyes of 64 patients who received LASIK were collected in Henan Eye Institute,Henan Eye Hospital from March to June 2011 with the equivalent spherical diopter of (-4.75±2.38)D and horizontal corneal diameter of (11.36±0.32)mm.Central corneal thickness was measured on each eye by using non-contact specular microscope (Topcon SP-3000P),slit-scanning pachymetry (Orbscan Ⅱ),AS-OCT and A-type ultrasound pachymetry,respectively,and the paracentral corneal thickness including 12:00,2:00,6:00 and 10:00 meridian was measured using Orbscan Ⅱ,non-contact specular microscope and AS-OCT.The measuring values and the agreement from different instruments were compared and evaluated.Results The mean central corneal thickness was (467.12±31.10)tμm for AS-OCT,(466.67±30.99)μm for ultrasound pachymetry,(441.84 ± 33.65) μm for specular microscopy and (422.51 ± 44.09) μm for Orbsan Ⅱ,respectively,showing a significant difference among the four methods (F =23.730,P =0.000).The central thickness value of the A-type ultrasound pachymetry was significantly higher than that of Orbsan Ⅱ or non-contact specular microscope (q =6.940,6.720,both at P =0.000).Compared with Orbscan Ⅱ,the measuring values of non-contact specular microscope and AS-OCT were significantly higher (q =-5.54,6.940,both at P =0.000),and the measuring value of AS-OCT was significantly higher that of non-contact specular microscope (q =6.800,P =0.000).The lowest difference value (25.3 μm)and the best agreement was found between the ultrasound pachymetry and AS-OCT.The paracentral corneal thickness values in 12:00,2:00,10:00,6:00 meridians were highest for Orbsan Ⅱ and the next for AS-OCT,and non-contact specular microscope had the lowest values,with significantly differences among them (F =5.020,22.950,67.890,18.850,all at P ＜ 0.01).Conclusions The corneal thickness values vary with the different instruments.Orbsan Ⅱ underestimates the central corneal thickness and overestimates the midperipheral corneal thickness,and non-contact specular microscope underestimates both the central and midperipheral corneal thickness.The measuring outcome from AS-OCT has a good agreement with ultrasound pachymetry and therefore they can be used interchangeably.

Utility of the Noncontact Specular Microscopy for Measurements of Central Corneal Thickness

PURPOSE: To evaluate the efficacy of noncontact specular microscopy (NCSM) by comparing the measurement of central corneal thickness (CCT) to the measurement with anterior segment optical coherence tomography (AS-OCT) and ultrasound pachymetry (USP). METHODS: One examiner measured the CCT of 50 eyes of 50 healthy young subjects using NCSM, AS-OCT, and USP. The mean values and correlations were analyzed. RESULTS: The mean CCT value was 546.92 +/- 32.06 microm with NCSM, 535.24 +/- 30.54 microm with AS-OCT, and 546.38 +/- 30.70 microm with USP. The CCT measurements with NCSM and USP were significantly thicker than with AS-OCT (p 0.900 in all groups, p < 0.001 in all groups). CONCLUSIONS: CCT measurements of healthy eyes using NCSM are more correlated with USP than AS-OCT. The CCT measurement using NCSM is a better alternative for USP than AS-OCT.

Corneal Thickness Measured by Dual Scheimpflug, Anterior Segment Optical Coherence Tomography, and Ultrasound Pachymetry

PURPOSE: To compare central corneal thickness (CCT) as measured by dual rotating Scheimpflug camera (Galilei), anterior segment optical coherence tomography (AS-OCT), and ultrasound pachymetry (USP). METHODS: The measurements of CCT using a dual rotating Scheimpflug camera, AS-OCT, and USP in 40 eyes of 20 healthy subjects were compared. RESULTS: The average measurements of CCT by dual rotating Scheimpflug camera, AS-OCT, and USP were 538.10 +/- 31.36 microm, 536.20 +/- 31.21 microm, and 541.93 +/- 34.93 microm, respectively. The CCT measurement by USP was statistically significantly thicker than by the dual rotating Scheimpflug camera and AS-OCT (p = 0.017, p = 0.001, respectively). There was no significant difference between the dual rotating Scheimpflug camera and AS-OCT (p = 0.054). A significant linear correlation was observed between the dual rotating Scheimpflug camera, the AS-OCT, and the USP (r > 0.900, p < 0.001). CONCLUSIONS: The results of the 3 methods have significant correlation with each other, but the measurement by USP was significantly thicker than the dual rotating Scheimpflug camera and AS-OCT. Therefore, CCT should be interpreted in the context of the instrument used.

Comparison of Flap Thickness Measured with Ultrasound Subtraction Method, Direct Method, and Optical Coherence Tomography

PURPOSE: To compare the flap thicknesses measured with the ultrasound (US) subtraction method, the direct method, and optical coherence tomography (OCT) in femtosecond laser-assisted LASIK eyes. METHODS: The present study included 65 eyes of 37 patients who underwent femtosecond laser-assisted LASIK surgery. Flap thickness was measured intraoperatively using the direct and subtraction methods with US pachymetry and postoperatively using anterior segment OCT. Flap thickness measurements were compared among the three methods. RESULTS: There was no significant difference between the flap thickness measured using the US subtraction method and OCT (p = 0.511). The flap thickness values obtained by these two different methods also correlated well with each other (gamma = 0.820, p < 0.001). However, flap thickness measured using the US direct method was significantly different (p < 0.001) with a low agreement value compared to the other two methods. Furthermore, the US direct method showed a lower measurement success rate compared to the US subtraction method (54% vs. 95%). CONCLUSIONS: Flap thickness measured using the US subtraction method and OCT showed different values compared to that measured using the US direct method. Because of the lower measurement success rate and agreement value, the US direct method is not capable of being used in substitute for the US subtraction method.

Comparison of central corneal thickness measurements with the Galilei dual Scheimpflug analyzer and ultrasound pachymetry.

Purpose: To compare corneal pachymetry assessment by the Galilei dual Scheimpflug analyzer with that done by ultrasound (US) pachymetry. Materials and Methods: Forty six patients (92 eyes) were subjected to corneal pachymetry assessment by Galilei dual Scheimpflug analyzer and US. All the readings were taken by a single operator. Intraoperator repeatability for the Galilei was assessed by taking 10 readings in one eye each of 10 patients. To study the interoperator reproducibility for the Galilei, two observers took a single reading in both the eyes of 25 patients. Results: The mean central corneal thickness (CCT) measured by US was 541.83 ± 30.56 μm standard deviation (SD) and that measured by Galilei was 541.27 ± 30.07 μm (SD). There was no statistically significant difference between both the methods (P < 0.001). The coefficient of repeatability was 0.43% while the coefficient of reproducibility was 0.377% for the Galilei. Conclusion: Objective, noncontact measurement of the CCT with the Galilei dual Scheimpflug analyzer was convenient, had excellent intraoperator repeatability and interoperator reproducibility, and findings were similar to those obtained with standard US pachymetry.

Comparison of Corneal Thickness and Anterior Chamber Depth Measured With Orbscan, Pentacam, and Ultrasound Pachymetry

PURPOSE:We compared the measurements of corneal thickness and anterior chamber depth (ACD) using three different methods Orbscan, Pentacam and ultrasound pachymetry. METHODS: In healthy volunteers, central corneal thickness was measured with Orbscan, Pentacam and ultrasound pachymetry. Estimation of peripheral corneal thickness and ACD were done by Orbscan and Pentacam. All results were compared statistically. RESULTS: The mean central corneal thickness of 64 eyes measured by Orbscan, Pentacam and ultrasound pachymetry were 509.1+/-61.0 microm, 539.2+/-51.7 microm and 527.4+/-48.3 microm, respectively. There were statistically significant differences in the results among the three methods (repeated-measures analysis of variance (ANOVA), p0.90, p<0.05). The temporal and nasal peripheral corneal thicknesses were thinner in the Pentacam than in the Orbscan (paired t-test, p<0.05). The superior and inferior corneal thickness and ACD were not significantly different. CONCLUSIONS: The results of the three instruments have significant correlations with each other, so all methods are clinically useful.

Utility of the Anterior Segment Optical Coherence Tomography for Measurements of Central Corneal Thickness

PURPOSE: To demonstrate the capability of anterior segment optical coherence tomography (OCT), to evaluate central corneal thickness (CCT) and to compare the results with those by Orbscan II and standard ultrasound (US) pachymetry. METHODS: One examiner measured the CCT of 44 normal eyes of 22 subjects using anterior OCT, Orbscan II, and US pachymetry. Non-contact measurements by anterior segment OCT and Orbscan II were performed first, followed by contact measurements using US pachymetry. Three consecutive measurements were taken with each method and the mean values and correlations were analyzed. RESULTS: The mean value of the CCT was 531.45+/-32.90 micrometer with anterior OCT, 537.11+/-32.21 micrometer with Orbscan II, and 548.18+/-34.17 micrometer with US pachymetry. There was no statistically significant difference among the values obtained by the 3 instruments (P>0.05). CCT measurements by anterior segment OCT were highly correlated with Orbscan II and US pachymetry (P<0.001) measurements. CONCLUSION: CCT measurements by anterior segment OCT are highly correlated with Orbscan II or US pachymetry measurements. Using non-contact anterior segment OCT, a closer examination of the anterior segment including the cornea is possible. The measurement of the CCT using anterior segment OCT is applicable because result values are similar to measurements by Orbscan II or US pachymetry.

Central Corneal Thickness before and after Excimer Laser Photore fractive Keratectomy in Myopia

This prospective study was done to investigate the correlation between central corneal thickness before excimer laser photorefractive keratectomy in myopic eyes and clinical factors including age, sex, left or right eye, myopic degree, and preoperative contact lens wearings, and also the relationship between the changes in postoperative central corneal thickness and age, sex, and myopic degrees. The average values of preoperative groups of less than -6.0D and over -6.0D were 519.78+/-29.87micrometer and 514.63+/-3 0.5 3 micrometerrespectively, showing much thinner value in high degree myopic eyes with statistical significance(p=0.02). Female patient's value was much thinner than male patient's value with statistical significance(p=0.016). The postoperative changes according to time process in central corneal thickness in 79 eyes which were followed up for more than six months were statistically significant(p=0.046). Among the changes in postoperative central corneal thickness, the recovery pace had no relations with age but female patient and over -6.0D in myopic degree showed faster recovery paces than male patient(p=0.035) and under -6.0D in myopic degree respectively during follow up period(p=0.001).

Difference of Corneal Thickness in Enucleated Eye

The maintenance of corneal endothelial cells is essential for success of corneal transplantation. Endothelial cell count by specular microscope and measurement of donor corneal thickness is useful in measuring the function of cornea. We studied difference of corneal thickness in central and peripheral corneal region in enucleated eye. We measured corneal thickness of 48 eyes(48 persons) with ultrasound pachymetry that were presented to The Eye Bank of Catholic University Medical College. Average age was 61.42+/-16.12 years and average time was 163.02+/-102.52 minutes until measurement of corneal thickness after death. Increased amount of corneal thickness was 136.73+/-101.44micrometer in center and 61.37+/135.46micrometer in periphery compared with normal average corneal thickness. According to these results, corneal edema due to functional loss of endothelial cells after death lead to increased corneal thickness, especially in central region being more statistically significant than peripheral region (p=0.002).