Mean Compare Central Corneal Thickness Research Articles

Comparison of central corneal thickness measurements using three different imaging devices

The purpose of this study was to compare central corneal thickness (CCT) values and evaluate the agreement obtained with three different devices in healthy eyes. A total of 120 eyes of 60 healthy individuals (36 men and 24 women) were enrolled in this retrospective study. CCT measurements were performed using an optical biometer (AL-Scan), spectral-domain optical coherence tomography (SD-OCT) (Topcon 3D) and ultrasonic pachymetry (UP) (Accupach VI), and the results were compared. Bland-Altman analysis was used to quantify the agreement between methods. The mean patient age was 28±5.73years (18-40years). The mean CCT values obtained by AL-Scan, UP, and SD-OCT were 532.4μm±29.7, 549μm±30.4, and 547μm±30.6, respectively. The mean differences in CCT were 15.30±9.52μm between AL-Scan and OCT (P<0.01), 17.15±8.42μm between AL-Scan and UP (P<0.01), and 1.85± 8.78μm between UP and OCT (P=0.067). All three methods of CCT measurement were closely correlated with each other. The present study results suggest that, despite good agreement between the three devices, AL-Scan significantly underestimated CCT compared to UP and OCT. Therefore, clinicians should be aware that different results can be obtained using different devices for CCT measurements. It would be a better approach not to use them as interchangeable in clinical practice. CCT examination and follow-up should be performed using the same device, especially for patients who will undergo refractive surgery.

Central Corneal Thickness of Diabetic Patients in Yaound&amp;#233;: Case Control Study

Background: To compare central corneal thickness (CCT) values measured in diabetic eyes and compare the CCT values in normal patients without diabetes. Methods: A total of 83 diabetic patients and 83 non-diabetic patients were prospectively enrolled in this comparative case series. CCT was measured using a Topcon CT-1P non-contact automated pachymeter, and values were compared. Results: Mean age was 57 ± 11 years, with a range of 23 and 80 years. The mean CCT was 508.87 ± 35.83 μm for diabetic patients and 513.41 ± 37.22 μm for non-diabetic patients. There was no statistically significant difference between the CCT of diabetic patients compared to non-diabetic patients (p = 0.260). We did not find a significant correlation between the CCT of diabetic patients and clinical characteristics of diabetes. However, there was a positive and statistically significant linear correlation between the CCT of diabetic patients and intra ocular pressure (IOP). Conclusion: The mean CCT in diabetic patients was lower than in non-diabetic control patients, although there was no statistically significant difference.

Blind spot in ultrasound central corneal thickness measurement – Central corneal thickness of apex versus central corneal thickness of vertex

Aims: This study aimed to compare central corneal thickness (CCT) using ultrasound pachymetry (USP) (CCT apex) and specular microscopy (CCT vertex) and also to find out the intra-reading variability from the two instruments. Settings and Design: A prospective, observational study was conducted in a tertiary eye care center in southern India. Materials and Methods: This study was conducted on 12 patients (24 eyes, 96 data set eyes, 768 data points in total) aged 20–50, in non-pathological corneas. Eight CCT measurements by specular microscopy and eight measurements by USP were taken by two different experienced observers on day 1, followed by repeating the same on day 2. Statistical Analysis: The readings were averaged and compared by paired t-test. SPSS software was used for statistical analysis. Variability between the eight readings produced by the same instrument was calculated and coefficient of variation was plotted. Inter-examiner variability and intra-examiner variability of the two modalities were studied, and it was considered statistically significant if P &lt; 0.05. Results: The mean CCT by USP was 522.71 µm and the mean CCT by specular microscopy was 519.43 µm. The coefficient of variation of the eight readings varied significantly between the machines. On an average, the coefficient of variation was 0.4% compared to 0.8% in specular microscopy and USP, respectively. Conclusion: The intra-reading variability of ultrasound CCT is twice as that compared to specular microscopy. The clinical relevance of this spread is relevant and important in modern-day practice. Hence, it is better advisable that CCT readings from both the modalities, not be used interchangeably.

Comparison of Central Corneal Thickness Measurements by Contact and Non-contact Pachymetry Devices.

Aim and objectiveTo compare central corneal thickness (CCT) measurements obtained by handheld contact ultrasound pachymetry (HCUP) and non-contact pachymetry devices.Materials and methodsNinety eyes of 90 patients (52 male and 38 female) were included in the study. Measurements from two non-contact devices, —specular microscopy (SM, Konan Medical, CA, USA) and Oculus Pentacam (Oculus Inc., Germany)—were compared against HCUP (Pachmate 2, DGH Technology, Inc, PA, USA). Ultrasound measurements were obtained 3 times by the same user and averaged. The differences were calculated by one-way ANOVA. Agreement between measurements were assessed by Bland–Altman plots and intraclass correlation coefficient tests. Coefficient of repeatability (%, CR) was defined as 1.96*standard deviations of the differences between pairs of measurements divided by the average of the means.ResultsThe mean age was 34.31 ± 14.39 (14–74) years, and the mean intraocular pressure was 16.48 ± 2.63 mm Hg (12–21). Mean CCT measured by HCUP, SM, and Pentacam was 557.76 ± 36.76 μm, 550.29 ± 43.74 μm, and 541.41 ± 35.7 μm, respectively (p < 0.05). In the Bland–Altman plot, 95% limit of agreements were 19.5 and 14.18 μm among HCUP measurements, 34.55 μm between HCUP and Pentacam, 41.49 μm between SM and Pentacam, and 46.98 μm between HCUP and SM. CR values (%) were 3.49, 2.54, 6.28, 7.68, and 8.47, respectively.ConclusionThere were significant differences between the mean CCT values of the measurement devices.Clinical significanceContact and non-contact devices may not interchangeable in the clinical assessment of CCT.How to cite this articleMayali H, Altinisik M, Diri I, et al. Comparison of Central Corneal Thickness Measurements by Contact and Non-contact Pachymetry Devices. J Curr Glaucoma Pract 2021;15(1):28–31.

A comparison of central corneal thickness measured using noncontact methods and ultrasonic pachymetry.

The aim of this study is to compare central corneal thickness (CCT) measurements in healthy eyes using ultrasonic pachymetry (UP) with values obtained using anterior segment spectral domain optical coherence tomography (SD-OCT), the Scheimpflug camera system, and noncontact specular microscopy. One hundred and twenty-five eyes of 117 healthy individuals (56 women, 61 men) were included. All patients underwent consecutive CCT measurement with UP, the Scheimpflug camera, anterior segment SD-OCT, and specular microscopy. The four devices could be read. Measurements from the four devices were classified in pairs and compared using the paired t-test. Relations between the devices were analyzed using the Pearson test. An alpha error level of P < 0.05 was regarded as statistically significant. The mean age of the healthy individuals included in the study was 34.75 ± 14.55 years (20-76). Mean CCT values were 541.21 ± 29.24 μm with UP, 539.26 ± 29.27 μm with the Scheimpflug camera system, 532.21 ± 29.53 μm with SD-OCT, and 534.45 ± 29.20 μm with specular microscopy. The differences in measurements at the paired t-test were statistically significant (P < 0.001 for all). However, measurements using the four devices exhibited significant mutual correlation (P < 0.001 for all). CCT can be measured using different devices. Noncontact methods have now begun replacing UP, regarded as the gold standard. Although CCT values obtained from different devices were correlated, the difference between these measurements was statistically significant. Therefore, the same device should be used for measurement in the diagnosis and follow-up of diseases such as corneal ectasia and glaucoma where corneal thickness is important.

Comparison of Anterior Ocular Biometric Measurements Using Swept-Source and Time-Domain Optical Coherence Tomography.

Purpose To compare central corneal thickness (CCT), aqueous depth (AQD), and anterior chamber depth (ACD) measurements using the swept-source (CASIA SS-1000, Tomey, Japan) and time-domain (Visante, Carl Zeiss Meditec, USA) anterior segment optical coherence tomographers (OCT) in normal eyes. Methods Sixty-eight eyes of 68 subjects were included. Three consecutive scans of each subject were obtained using both devices in a random order by one experienced operator. Standard deviation (Sw), coefficient of repeatability (CoR), coefficients of variation (CoV), and intraclass correlation coefficients (ICC) were used to evaluate the intraoperator repeatability. Agreement was assessed using the Bland–Altman plots and 95% limits of agreement (LoA). Results All measurements of the swept-source OCT (SS-OCT) and time-domain OCT (TD-OCT) showed high repeatability with low CoR (CCT: 2.34 μm and 6.16 μm; AQD: 0.05 mm and 0.09 mm; ACD: 0.06 mm and 0.09 mm), low CoV (CCT: 0.16% and 0.42%; AQD: 0.61% and 0.97%; ACD: 0.53% and 0.83%), and high ICC (>0.98). The mean CCT with SS-OCT was slightly thicker than the results with TD-OCT (difference = 4.55 ± 2.62 μm, P < 0.001). There was no statistically significant difference in AQD or ACD measurements between the two devices (0.01 ± 0.05 mm, P=0.111; 0.02 ± 0.05 mm, P=0.022, respectively). The 95% LoA between the SS-OCT and TD-OCT were −0.59 to 9.69 μm for CCT, −0.10 to 0.12 mm for AQD, and −0.09 to 0.12 mm for ACD. Conclusions High levels of repeatability and agreement were found between the two devices for all three parameters, suggesting interchangeability. SS-OCT demonstrated superior repeatability compared with TD-OCT.

Comparison of Central Corneal Thickness Measured by Standard Ultrasound Pachymetry, Corneal Topography, Tono-Pachymetry and Anterior Segment Optical Coherence Tomography

ABSTRACTPurpose: To compare central corneal thickness (CCT) measured by standard ultrasound pachymetry (USP), and three non-contact devices in healthy eyes.Methods: A cross-sectional study of CCT measurement in 52 eyes of 52 healthy volunteers was done by a single examiner at Ocular Surface and Contact Lens Laboratory. Three consecutive measurements were done by standard USP, non-contact tono-pachymeter, Pentacam corneal topographer, and Anterior Segment Optical Coherence Tomography (AS-OCT). The mean values were used for assessment. The results were compared using multivariate ANOVA, linear regression, and Pearson correlation. Agreement among the devices was analyzed using mean differences and Bland–Altman analysis with 95% limits of agreement (LoA). Finally, reliability was analyzed using intraclass correlation coefficient (ICC).Results: Mean CCT by ultrasound pachymeter, tono-pachymeter, corneal topographer and AS-OCT were 558.9 ± 31.2 µm, 525.8 ± 43.1 µm, 550.4 ± 30.5 µm, and 545.9 ± 30.5 µm respectively. There was a significant positive correlation between AS-OCT and USP (Pearson correlation = 0.957, p < 0.001), corneal topography and USP (Pearson correlation = 0.965, p < 0.001), and corneal topography and AS-OCT (Pearson correlation = 0.965, p < 0.001). There was a lower correlation between CT-1P tono-pachymeter and the other three modalities. Intraclass correlation coefficients show an excellent reliability between pairs except for CT-1P against the other three instruments that were found moderate.Conclusions: CT-1P tono-pachymeter underestimates CCT measurements compared to Scheimpflug system, AS-OCT device, and USP. Mean CCT among USP, Pentacam and AS-OCT were comparable and had significant linear correlations. In clinical practice, these three modalities could be interchangeable in healthy patients.

Canine central corneal thickness measurements via Pentacam-HR® , optical coherence tomography (Optovue iVue® ), and high-resolution ultrasound biomicroscopy.

To compare central corneal thickness (CCT) values in canine eyes using Pentacam-HR® Scheimpflug imaging (Pentacam), Optovue® iVue spectral-domain optical coherence tomography (SD-OCT), and high-resolution ultrasound biomicroscopy (UBM) and generate normative canine Pentacam CCT values. Twenty-four client-owned dogs (37 eyes) with nondiseased cornea(s) presenting to the Colorado State University Veterinary Teaching Hospital. Corneal images were acquired via Pentacam, SD-OCT, and UBM in the listed order. Machine-calculated values of CCT from Pentacam and SD-OCT were compared to operator-measured values from UBM. Bland-Altman analysis was performed to evaluate agreement between instruments. Mean CCT ± SD measured by Pentacam was 629.73 ± 64.57 μm, by SD-OCT was 610.56 ± 57.48 μm, and by UBM was 689.77 ± 55.93 μm. On average, Pentacam CCT was 19.17 ± 32.90 μm (3%) thicker than SD-OCT and 65.12 ± 44.52 μm (10.3%) thinner than UBM. SD-OCT was on average 82.47 μm (13.5% ) thinner than UBM. The 95% limits of agreement were (-45.31, 83.65), (-152.38, 22.13), and (-126.674, -38.270) for Pentacam vs. SD-OCT, Pentacam vs. UBM, and SD-OCT vs. UBM respectively. All differences were statistically significant (P < 0.01). Considering there is an average of 7.5% normal diurnal variation in canine CCT, a 3.0% difference between Pentacam and SD-OCT values is likely not clinically relevant. However, Pentacam measurements were both statistically and clinically significantly different from UBM and SD-OCT measurements.

A comparative study of central corneal thickness measurement in four different groups by specular microscope

Background: A prospective, randomized, single-site clinical trial conducted on patients attending our eye outpatient department. Objective: To compare central corneal thickness (CCT) measurements by noncontact specular microscope in young, elder, cataract, and chronic primary open-angle glaucoma (POAG) patients. Materials and Methods: Total 120 patients were selected which were divided into four groups of 30 patients in each group, i.e., Group A, B, C, and D. CCT was measured by noncontact specular microscopy. Group A was considered control group for rest of the groups while Group B was considered as a control for Group C and D. The P value was calculated using student paired t-test and P < 0.005 was considered significant. Results: In our study, out of 120 patients 74 (61.66%) were male while 46 (38.33%) were female. Male predominance is seen in all groups. In Group A the mean CCT was 545.17 ± 31.43 μm, in Group B it was 547.67 ± 21.16 μm, in Group C CCT was 524.03 ± 27.48 μm while in Group D it was 467.53 ± 31.21 μm. POAG patients have significantly lesser CCT as compared to other three groups. Conclusion: In this study, no significant difference in CCT of male and female was seen. Aging and cataract had no significant effect on CCT. Glaucoma patients had significantly lower CCT than young patients (P < 0.001) and elder patients (P < 0.001). It concludes that POAG patients have thinner cornea.

Changes in Corneal Thickness and Specular Microscopic Indices in Acute Unilateral Anterior Uveitis

Purpose: To compare central corneal thickness (CCT) and specular microscopic indices in active unilateral anterior uveitis with the same indices 1 week after the initiation of treatment. Methods: This study included 30 eyes with active unilateral idiopathic anterior uveitis. CCT and specular microscopic indices were compared before and after 1 week of the treatment with topical medications.Results: At the first visit, mean CCT was significantly greater in affected eyes (mean ± standard deviation: 514.0 ± 23.0) than in fellow eyes (493.2 ± 10.6) (p < 05). There was a significant decrease in CCT of the involved eye 1 week after start of treatment to 494.1 ± 23.1 μm (p < 05). No significant differences were observed in the specular microscopic indices between the affected and fellow eyes before treatment and 1 week after the treatment.Conclusion: We found that eyes with unilateral active anterior uveitis had increased CCT in comparison to their healthy fellow eyes without a change in the specular microscopic indices.

Differences in Central Corneal Thickness between Spectral Domain-Optical Coherence Tomography and Ultrasound Pachymetry in Patients with Dry Eye Disease.

Purpose. To compare central corneal thickness (CCT) values via Spectral Domain-Optical Coherence Tomography (SD-OCT) and ultrasonic pachymetry in patients with severe dry eye disease (DED) to determine the level of agreement between these 2 methods. Methods. The paired samples t-test was used to compare CCT values in severe DED patients. Matching analysis between methods was performed using intraclass correlation coefficient (ICC). Intrasession reliability of the measurement methods was calculated via the concordance correlation coefficient (CCC), variation equivalent, and Pearson's correlation coefficient. The Bland-Altman procedure was used to graphically represent the differences between CCT values. Results. The study included 56 eyes of 24 female and 4 male patients. Mean age of the patients was 50.9 ± 11.3 years. Mean CCT via Cirrus SD-OCT was 523.82 ± 30.98 μm versus 530.050 ± 31.85 μm via ultrasonic pachymetry (paired samples t-test, P < 0.001). The Bland-Altman plot showed good agreement between the examiners. The ICC for repeatability was 0.974. The CCC between the 2 methods' CCT values was 0.973. The variation equivalent was 0.976 and Pearson's correlation coefficient was 99.3%, which also indicated high correlation between the 2 methods' measurements. Conclusions. The present findings show that in patients with severe DED Cirrus SD-OCT provides reliable intraobserver CCT values.

Comparison of Central Corneal Thickness Measurement Using Non-Contact and Contact Pachymetry Devices in Normal Eyes

Purpose: To compare central corneal thickness (CCT) in normal population using contact and non-contact pachymetry devices and to assess the intra operator repeatability of measurement with each device. Materials and Methods: This prospective, cross sectional comparative study evaluated 30 healthy subjects fulfilling the inclusion criteria reporting in AFIO Rawalpindi. CCT was measured in both eyes of subjects using noncontact specular microscope, Dual Scheimpflug analyzer and contact ultrasound pachymeter by a single investigator at the same time of the day. Pearson’s correlation coefficient test was performed to ascertain correlation between pachymetry devices. Intra operator repeatability was analysed using within subjects coefficient of variation/repeatability (CoV) and intra class correlation coefficient (ICC). Results: Sixty eyes of 30 male subjects were analysed. Mean age of study population was 31.03 ± 10.30 years. Mean CCT values were 536.48 ± 35.77 µm, 498.62 ± 34.70 µm and 526 ± 37 µm with Dual Scheimpflug Analyzer , Specular microscope and Ultrasonic pachymeter respectively (p 0.90). Conclusion: All three devices showed excellent intra operator repeatability for CCT measurement making them reliable tools for CCT measurement. Key Words: Central Corneal Thickness, Pachymetry, Repeatability, Microscopy.

Comparison of Central Corneal Thickness Measurements Obtained by RTVue OCT, Lenstar, Sirius Topography, and Ultrasound Pachymetry in Healthy Subjects

ABSTRACTPurpose: To compare central corneal thickness (CCT) measurement results obtained by RTVue OCT, Lenstar, Sirius topography, and ultrasound pachymetry (UP) (OcuScan RxP Ophthalmic Ultrasound System, Alcon Laboratories) in healthy subjects. Materials and Methods: 256 eyes of 128 healthy subjects were included in the study. CCT measurements were obtained from the eyes for each subject using the UP, Lenstar, Sirius topography, and RTVue OCT instruments. Ultrasound pachymetry measurements were performed after the eyes were anesthetized with one drop of 0.5% proparacaine hydrochloride and were performed at the same day after 15 minutes after previous measurements. Results: Of 128 participants, 84 were male and 44 were female with a mean age of 33.15 ± 12.95 years (ranging from 18 to 75 years). The mean CCTs for UP, Lenstar, Sirius topography, and RTVue OCT were 535.60 ± 35.15 (440,00–668,00); 532.63 ± 34.44 (449,00–650,00); 526.05 ± 36.45 (314,00–640,00); 525.89 ± 33.21 (437,00–646,00) µm, respectively. The mean CCT measurements were statistically different among the three groups (p = 0.002). CCT measurements obtained using RTVue-OCT were significantly thinner than those obtained using UP (p = 0.009). Sirius CCT measurements were also thinner than UP (p = 0.011). Mean CCT measurements between UP and Lenstar were similar (p = 0.769). Measurements with Lenstar (r = 0.849), Sirius topography (r = 0.883), and RTVue OCT (0.949) were highly correlated with UP measurements. Conclusion: RTVue OCT and Sirius topography significantly underestimated the CCT compared with UP. Although highly correlated, the measurement values with these devices are not directly interchangeable in clinical practice.

Effect of the eyelid speculum on pachymetry during corneal collagen crosslinking in keratoconus patients

To compare central corneal thickness (CCT) with and without using an eyelid speculum during corneal collagen crosslinking (CXL). University Medical Center Utrecht, Utrecht, the Netherlands. Prospective nonrandomized comparative study. Eyes with progressive keratoconus were treated by CXL and consecutively divided into 2 groups. In Group A, an eyelid speculum remained in place throughout the entire CXL procedure. In Group B, the eyelids remained closed during the 30-minute riboflavin instillation. Intraoperative ultrasound pachymetry measurements were performed at different timepoints. The visual acuity, refraction, keratometry, pachymetry, and endothelium were evaluated 6 months after CXL. The main outcome measures were intraoperative CCT measurements and the clinical CXL effect after 6 months. Fifty-two eyes (50 patients) were treated. After riboflavin instillation, a statistically significant difference in CCT reduction was found between the 2 groups (P<.001), with a mean CCT decrease of 62 μm±53 (SD) (13%±11%) in Group A and 11±35 μm (2%±8%) in Group B. No statistically significant between-group differences were found after epithelial removal or ultraviolet-A (UVA) irradiation. Six months after CXL, no statistically significant between-group difference was found in the visual acuity, refraction, keratometry, pachymetry, or endothelium. Avoidance of an eyelid speculum during riboflavin instillation resulted in less CCT reduction during CXL. This finding could increase the chance of attaining the required pachymetry safety margin for applying UVA and thus decrease the chance of premature CXL treatment termination. No author has a financial or proprietary interest in any material or method mentioned.

Comparison of anterior segment measurements using rotating Scheimpflug imaging and partial coherence interferometry.

To compare central corneal thickness (CCT) and anterior chamber depth (ACD) measurements using rotating Scheimpflug imaging and partial coherence interferometry. As part of the first phase of Shahroud Eye Cohort Study with 5 190 subjects of 40 to 64 years of age, CCT and ACD were measured using Scheimpflug imaging with the Pentacam (Oculus, Inc., Lynnwood, WA, USA) and partial coherence interferometry with the Allegro BioGraph (Wavelight, Erlangen, Germany). After applying exclusion criteria, we had data of 4 387 subjects with a mean age of 50.7±6.2 years. Mean CCT with Pentacam and BioGraph were 528.6±33.2µm and 525.6±32µm respectively; the difference was statistically significant (P<0.001), but the correlation was high (R=0.920). Mean ACD measurements using Pentacam and BioGraph were 2.68±0.35mm and 2.62±0.33mm respectively; the inter-device difference was significant (P<0.001) with high correlation (R=0.944). The 95% limits of agreements between devices were -22.65µm to 28.61µm and -0.16mm to 0.29mm for CCT and ACD measurements, respectively. For both CCT and ACD, the BioGraph gave significantly lower values than the Pentacam (P<0.05). Despite the high inter-device correlation, the 95% limits of agreements were wide, and this may limit their interchangeability in measuring the CCT and ACD.

Central corneal thickness measurements in normal dogs: a comparison between ultrasound pachymetry and optical coherence tomography

To compare central corneal thickness (CCT) measurements obtained from normal canines using a spectral-domain optical coherence tomography device (SD-OCT) and an ultrasonic pachymeter. Fifteen clinically normal dogs. Dogs were briefly anesthetized with propofol. Central corneal thickness measurements were obtained from both eyes of each animal four times by one operator using a SD-OCT system. The CCT was automatically calculated using the pachymetry software generated from eight radial scans, 6 mm in length. Ultrasonic pachymetry was then performed in both eyes of each animal by one operator five times in succession. The CCT was recorded for each modality and compared statistically for agreement and bias. Fifteen dogs (seven castrated male, eight spayed female) with a mean age of 2.3 ± 1.3 years were examined. The mean CCT for all eyes examined via SD-OCT and ultrasonic pachymetry (velocity set at 1636 m/s) was 587.72 ± 32.44 μm and 598.54 ± 32.28 μm, respectively. Ultrasonic pachymetry consistently overestimated CCT as compared to OCT by a mean value of 10.82 μm (P < 0.0001). No significant difference in CCT was found based on the age or sex of the animal. There was no significant difference in CCT measurements between replicates performed by the same operator for each modality. The coefficient of variation within and between imaging modalities was low (range 0.63-2.5%). The intraclass correlation coefficient comparing methods was 0.92. Correlation between modalities was excellent; however, ultrasonic pachymetry set at a standard velocity of 1636 m/s overestimates CCT as compared to OCT.

Evaluation of central corneal thickness after cataract surgery, penetrating keratoplasty and long-term soft contact lens wear

The aim of this study was to compare central corneal thickness (CCT) between corneas of normal healthy eyes (cNHE), corneas of eyes that had undergone cataract surgery by clear corneal phacoemulsification with implantation of an intracapsular intraocular lens (cIOL), corneal grafts after penetrating keratoplasty (gPK) and corneas of long-term soft contact lens wearers (cCL). The study design was a consecutive cross-sectional trial. CCT was measured using rotating Scheimpflug camera (Pentacam, software version 1.16r04) in 80 cNHE, 79 cIOL, 46 gPK and 78 cCL. Analysis of variance (one-way ANOVA) was performed to compare differences of mean values between these four groups. Pearson's or Spearman's correlation coefficient (r) was determined between CCT value and age, follow up time after penetrating keratoplasty (timePK) or contact lens wearing time (timeCL). Means of CCT measurements were comparable between cNHE (mean CCT±standard deviation, 554±36μm), cIOL (551±40μm) and gPK (534±52μm) as determined by one-way ANOVA. Mean CCT values in cCL (537±37μm) were statistically significantly lower in comparison to cNHE (p=0.026, 95% CI=1.43-31.44). There was no linear correlation between age and CCT values of cNHE and cIOL (p=0.841, r=-0.031 and p=0.931, r=0.011, respectively). No linear relationship was determined between CCT values of cCL and timeCL (p=0.315, r=-0.125). CCT values of gPK did not correlate with timePK (p=0.738, r=0.054). The data reported here indicate that in the same statistical model among CCT values of cNHE, cIOL and gPK only long-term soft contact lenses (CL) wearer have significantly lower CCT measurements.

Comparative Study of Central Corneal Thickness Using Fourier-Domain Optical Coherence Tomography Versus Ultrasound Pachymetry in Primary Open-Angle Glaucoma

To compare central corneal thickness (CCT) results measured by Fourier-domain optical coherence tomography (FD-OCT) and ultrasound pachymetry (USP) in glaucomatous eyes. In this prospective, observational cross-sectional study, 80 eyes of 80 patients with primary open-angle glaucoma (POAG) and no other ocular abnormality were selected: 28 were treated with 1 drug (subgroup 1), 32 with 2 drugs (subgroup 2), and 20 with 3 drugs (subgroup 3). CCT was measured by FD-OCT (RTVue OCT) and USP (Pachymeter Reichert IOPac). Bland-Altman plots were used to assess the agreement between both instruments. The differences between CCTs measured by USP and FD-OCT were compared among the 3 subgroups. The mean CCT was 537.76 ± 32.24 μm and 520.53 ± 30.44 μm for USP and FD-OCT, respectively. A significant difference was found between the mean values obtained by FD-OCT and USP (17.22 ± 7.96 μm, P < 0.001, paired Student t test). A high correlation was obtained for CCT measured by both methods (Pearson correlation coefficient = 0.969; P < 0.001), and there was good agreement between the 2 pachymetry methods. Similar differences in CCT using USP and FD-OCT were found among the 3 treatment subgroups (P > 0.05 in all pairwise comparisons, analysis of variance). FD-OCT underestimates CCT compared with CCT measured by USP in POAG. Although highly correlated, the difference between these 2 devices can be clinically significant in the context of refractive surgeries in POAG patients but not in intraocular pressure estimation. This difference also seems to be independent of the number of antiglaucoma treatments used.

A Study of Central Corneal Thickness in Glaucoma and Nonglaucoma Patients in a West African Population

To compare central corneal thickness (CCT) in high-tension glaucomatous eyes and nonglaucomatous eyes with normal intraocular pressure (IOP) and to determine if there is any correlation between CCT and severity of glaucoma, as indicated by vertical cup-to-disc ratio. A case-control study that involved 506 subjects at the Korle-Bu Teaching Hospital, Accra, Ghana, from August 2006 to July 2007. The cases were patients with (high tension and IOP more than 21 mm Hg) primary open-angle glaucoma, and the controls were patients with normal IOP (less than 21 mm Hg) and no evidence of glaucoma. The main outcome measures were CCT, as measured by ultrasonic pachymetry (model DGH 55 pachmate), and vertical cup-to-disc ratio. Five hundred six subjects were recruited: 253 cases (506 eyes) and 253 controls (505 eyes). The mean CCT of the right eye for the glaucoma cases was 524.28 μm [95% confidence interval (CI), 4.44; SD, 36.85] and for the controls was 530.00 μm (95% CI, 4.56; SD, 35.75). The mean CCT of the left eye for the glaucoma cases was 524.70 μm (95% CI, 4.48; SD, 36.20) and for the controls was 531.06 μm (95% CI, 4.40; SD, 35.52). The relation between CCT and cupping determined by Pearson correlation coefficient yielded values of -0.09 and 0.01 for the right and left eyes, respectively. There was no significant difference between mean CCT of cases and controls in the right eye (P = 0.08), but there was a weakly significant difference in the CCT of the left eye (P = 0.05). Also, there was no correlation between cup-to-disc ratio and CCT.

Central corneal thickness in Iranian congenital glaucoma patients

Purpose:To compare central corneal thickness (CCT) in subjects with controlled primary congenital glaucoma (PCG) and nonglaucomatous subjects and to investigate the correlation between CCT and intraocular pressure (IOP) in the study population.Materials and Methods:Twenty-three consecutive PCG cases with controlled IOP and no clinical evidence of corneal edema comprised the Study Group. There was an interval of at least 2 months between last intraocular surgery and inclusion in the study. Twenty-one subjects with strabismus or lacrimal drainage insufficiency who did not have glaucoma or any history of intraocular surgery or ocular trauma comprised the control group. The Control Group was age and sex-matched. Data from ultrasonic pachymetry and applanation tonometry were analyzed for differences between groups. Correlation of the study parameters was investigated. A P-value less than 0.05 was statistically significant.Results:Data from both eyes of subjects in the Study Group and Control Group were included in the original analysis. Mean CCT was statistically significantly higher in the Study Group compared to the Control Group (589.42 ± 53.44 μm vs. 556.14 ± 30.51 μm, respectively; P=0.001). There was a significant correlation between CCT and IOP (r=0.63; P<0.0001). Similar statistically significant outcomes were observed when only one eye per subject was used in a reanalysis of the data for the Study and Control Groups.Conclusion:Patients with PCG who had controlled IOP have statistically significantly thicker corneas than nonglaucomatous age and sex-matched subjects The thicker cornea could significantly alter IOP measurement with applanation tonometry. Pachymetry should be considered an essential part of the evaluation for PCG.