Central Corneal Thickness Measurements Research Articles

Intrasession repeatability and agreement of the anterior corneal assessment provided by a multidiagnostic device

ABSTRACT Clinical relevance Multidiagnostic systems have recently appeared on the market. Knowledge of the repeatability and validity of any instrument is mandatory before its introduction in clinical practice. Background The aim of this work is to examine the intrasession repeatability of anterior pole measurements provided by the multidiagnostic device Wave Analyzer Medica 700 (WAM700) and agreement with Pentacam measurements in normal eyes. Methods In the right eyes of 113 participants, three repeat measurements of central keratometry, central corneal thickness, anterior chamber depth and corneal eccentricity were made with the WAM700 and Pentacam in random order. Intrasession repeatability and agreement were determined. Results Employing WAM700, intrasession repeatability for keratometry, central corneal thickness and anterior chamber depth was good (ICCs ≥ 0.992; CV 0.48–0.98%), yet worse than the values obtained for the Pentacam (ICCs ≥ 0.998; CV 0–0.33%). WAM700 showed excellent intrasession repeatability when used to measure the anterior chamber depth (Sw 0.03 mm). However, the repeatability of this device was inferior for central corneal thickness (Sw 4.24 μm) and keratometry measurements (Sw < 0.21 D) and was poor for corneal eccentricity (Sw 0.07; ICC 0.908; CV 14.58%). Agreement between WAM700 and Pentacam showed a high ICC for the keratometry measurements, central corneal thickness and anterior chamber depth (>0.972) but lower for corneal eccentricity (ICC 0.762). Conclusions In healthy eyes, the WAM700 multidiagnostic device showed good intrasession repeatability for keratometry, central corneal thickness and anterior chamber depth measurements. Agreement between WAM700 and Pentacam was good for the anterior chamber depth measurement. However, these instruments cannot be considered interchangeable for keratometry, central corneal thickness and eccentricity readings.

A comparative study of central corneal thickness in patients with diabetes and without diabetes mellitus

Diabetes mellitus (DM) is becoming increasingly and seriously prevalent lifestyle health problem worldwide. Up to 70% of diabetic patients can develop corneal changes and are also difficult to manage. Several studies were done to find out the morphological changes in cornea in type 2 DM, but the results are highly variable. Central corneal thickness (CCT) is widely considered as a constant parameter, so are measured only once during follow up in our daily clinical practice. Here we study the effect of diabetes over CCT, for a better understanding of the impact of diabetes over CCT.A comparative observational study of one and half years done among 106 diabetes and 106 non diabetic patients between 35 to 75 years old, attending ophthalmology OPD. CCT of both eyes was measured and mean CCT and was compared between diabetic and non-diabetic groups, among different subgroups of diabetic subjects and other parameters.CCT was thicker among diabetic groups (553.4434um) than non-diabetic groups (549.8491) but was not statistically significant according to our study. But there was statistically significant (p value 0.000165) thickening with increasing grades of diabetic retinopathy (DR) (mild DR (535.4524), moderate DR (543) and PDR (591.5)). Our study concludes that DM is associated with thicker cornea; hence CCT values can vary with time in DM. So repeated CCT measurements for corrected IOP values is advised and warranted in DM patients for proper management of IOP.

Correlation of Central Corneal Thickness with Refractive Error, Corneal Curvature, and Axial Length: An Observational Study

Background: Various demographic and ocular factors influence central corneal thickness (CCT). Studies on the relationships between these parameters have shown conflicting results. We aim to investigate the correlation of CCT with different types of refractive error, axial length (AL), and corneal curvature. Materials and Methods: An observational study was undertaken in the Department of Ophthalmology, recruiting patients from 18 to 40 years of age with myopia (−0.5 D to −6 D) or hypermetropia (≤ +3 D) or emmetropia (−0.25 D to +0.25 D). All participants underwent comprehensive ophthalmic examination, including refraction, slit lamp examination and fundoscopy, followed by CCT, corneal curvature, and AL measurement. Result: A total of 1224 eyes of 612 patients (260 males and 352 females) were enrolled in the study. Out of them, 31.5% (n = 386) had emmetropia, 28.6% (n = 350) had hypermetropia, and 39.9% (n = 488) had myopia. The mean (±standard deviation [SD]) keratometry (K), CCT and AL were found to be 44.08 (±1.55) D, 528.46 (±29.78) μm, and 22.75 (±1.21) mm, respectively. With increasing age, CCT was found to be decreased (P &lt; 0.001). Compared to myopia, a significantly higher CCT was noted in hypermetropia (P &lt; 0.001). There was a negative correlation between CCT and corneal curvature among the entire study population, irrespective of their refractive status (P &lt; 0.001). This correlation was more significant among emmetropes and hypermetropes as compared to myopes. However, we found no correlation between CCT and AL in any groups. Conclusion: CCT is found to be thicker in hypermetropia and thinner in myopia as compared to emmetropia. With increasing age, the cornea tends to become steeper and thinner.

Repeatability and agreement of AOCT-1000 M, RTVue XR and IOL master 500 in measuring corneal thickness mapping and axial length applying principle of optical coherence tomography

PurposeTo evaluate the repeatability and agreement of Fourier-domain optical coherence tomography (AOCT-1000 M and RTVue XR) and partial coherence interferometry biometer (IOL Master 500) in measuring corneal thickness mapping and axial length respectively.MethodsCorneal thickness was measured by AOCT-1000 M and RTVue XR. Axial lengths were measured by AOCT-1000 M and IOL Master 500. The repeatability and agreement of corneal thickness and axial length were calculated in two groups of devices. The intraclass correlation coefficient (ICC) was used to verify the repeatability of the device. The 95% confidence interval of the difference compared to the set cut-off value was used to verify the agreement between the two devices.ResultsA total of 60 subjects with 58 eyes were included. The central corneal thickness measured by AOCT-1000 M and RTVue XR were 504.46 ± 42.53 μm and 504.43 ± 42.89 μm respectively. The average difference between groups was 0.03 ± 4.58 μm, and the 95% confidence interval was (-1.17, 1.24), which was far less than the set threshold value of 15 μm (P < 0.001). Both RTVue XR and AOCT-1000 M had very good ICC values of central corneal thickness (0.998 and 0.994, respectively). The average axial lengths measured by AOCT-1000 M and IOL Master 500 were 24.28 ± 1.25 mm and 24.29 ± 1.26 mm respectively and the 95% confidence interval was (-0.02, 0.01), which was less than the set threshold value of 0.15 mm (P < 0.001). The ICC for both devices were 1.000.ConclusionGood repeatability and agreement were seen in measurements of central corneal thickness and axial length by AOCT-1000 M.

Central Corneal Thickness and Intraocular Pressure in Children with Type I Diabetes Mellitus.

The aim of this study is to determine the mean central corneal thickness (CCT) and mean intraocular pressure (IOP) in children with type 1 diabetes mellitus (T1DM) and to determine the relationship between CCT and IOP on the one hand and age, gender, retinopathy hemoglobin A1c (HbA1c), and duration of diabetes on the other. This is a case-control, hospital-based study conducted at Hospital ___________ between January and November 2022. Thirty-eight children with T1DM were recruited as cases, and 38 healthy children were recruited as controls. The cases and controls then underwent ophthalmic examination, IOP measurement, and CCT measurement using optical coherence tomography (OCT) of the right eye. The IOP measurements were adjusted for CCT for further analysis. The means CCT and IOP values were significantly higher in the T1DM group than in the control group (p-value<0.02 respectively). The mean CCT was 542.18 ± 20.40 µm in the T1DM group, and 529.52 ± 26.17 µm in the control group. The mean IOP was 14.68 ± 1.98 mmHg in the T1DM group, and 13.52 ± 1.66 mmHg in the control group. The mean HbA1c was 10.68 ± 2.49% in the T1DM group. Age and duration of diabetes mellitus (DM) were found to have a significant association with CCT in children with T1DM. The duration of DM was also found to be significantly associated with the IOP. Gender and HbA1c levels were found to have no significant relationship with either CCT or IOP. Children with T1DM have significantly higher CCT and IOP than the average child. The duration of DM is a significant factor that impacts both CCT and IOP. In addition, age is another factor that affects CCT in children with T1DM.

Repeatability and reliability of semi-automated anterior segment-optical coherence tomography imaging compared to manual analysis in normal and keratoconus eyes.

To assess the repeatability and reliability of semi-automated EyeMark Python program measurements compared to manual ImageJ image processing of anterior segment-optical coherence tomography (AS-OCT) structures in healthy and keratoconus eyes. Heidelberg AS-OCT was used to image 25 eyes from 14 healthy subjects and 25 eyes from 15 subjects with keratoconus between the ages of 20 and 80years, collected prospectively, in this observational case-control study. Visual axis scan containing vertical fixation light beam was selected from the 15-line AS-OCT scan raster. Central corneal thickness (CCT), anterior corneal radius of curvature (ACRC), posterior corneal radius of curvature (PCRC), and truncated anterior vault (TAV) were measured using ImageJ software and the EyeMark Python program. MedCalc and R were used to calculate the intraclass correlation coefficient (ICC) and generate Bland-Altman plots (BAP). When comparing the measurements of CCT, ACRC, PCRC, and TAV between manual ImageJ analysis and the EyeMark Python program, ICC values were consistently greater than 0.9, indicating excellent agreement. BAPs comparing the ImageJ and Python measurements of anterior segment structures show no systematic proportional bias and the average differences were near zero and within 95% of the limits of agreement. Semi-automated tools may provide the necessary efficiency for point-of-care quantitative corneal analysis of raw AS-OCT images. The semi-automated EyeMark Python program offers a repeatable and reliable tool compared to manual ImageJ analysis for measuring anterior segment structures from AS-OCT images among individuals with keratoconus.

The influence of topical anesthetic and fluorescein on non-contact tonometry measurements using ultra-high-speed dynamic Scheimpflug

This study aimed to investigate the effects of topical anesthetic and fluorescein drops on intraocular pressure (IOP), central corneal thickness (CCT) and biomechanical properties as measured by Corvis ST (CST-Oculus; Wezlar, Germany) in healthy eyes. A cross-sectional observational study was conducted on 46 healthy patients. The CST measurements were obtained before and immediately after the instillation of topical anesthetic and fluorescein drops. Pre-post instillation data were statistically analyzed. IOP measurements were compared to Goldmann's Applanation Tonometry (GAT), which was also performed after drops instillation. Biomechanical parameters analyzed included applanation 1 velocity, applanation 2 velocity, applanation 1 time, applanation 2 time, whole eye movement, deflection amplitude, and stiffness parameter at first applanation. A statistically significant difference in IOP, both for non-corrected IOP (IOPnct) and biomechanically corrected IOP (bIOP), was observed before and after the instillation of eyedrops. Despite this statistical significance, the observed difference lacked clinical relevance. The IOPnct demonstrated a significant difference pre and post-anesthetic and fluorescein instillation compared to GAT (14.99 ± 2.27 mmHg pre-instillation and 14.62 ± 2.50 mmHg post-instillation, versus 13.98 ± 2.04 mmHg, with p-values of 0.0014 and 0.0490, respectively). Comparable findings were noted when justaposing bIOP to GAT (14.53 ± 2.10 mmHg pre-instillation and 13.15 ± 2.25 mmHg post-instillation, against 13.98 ± 2.04 mmHg, with p-values of 0.0391 and 0.0022, respectively). Additionally, CCT measurements revealed a statistically significant elevation following the administration of topical anesthetic and fluorescein drops (from 544.64 ± 39.85 µm to 586.74 ± 41.71 µm, p < 0.01. None of the analyzed biomechanical parameters showed statistically significant differences after drops instillation. While the administration of topical anesthetic and fluorescein drops induced a statistically significant alteration in both IOPnct and bIOP readings, these changes were not clinically consequential. Furthermore, a notable statistical rise was observed in CCT measurements post-drops instillation, as determined by CST. Yet, corneal biomechanical parameters remained unaffected.

Corneal Parameters Measurement in Healthy Subjects Using Scheimpflug and Anterior Segment Optical Coherence Tomography

Purpose: To compare the central corneal thickness (CCT),minimum corneal thickness (MCT) and corneal power measured using theScheimpflug-Placido device and optical coherence tomography (OCT) in healthy eyes. Study Design: Descriptive observational. Place and Duration of Study: Al-Kindy college of medicine/university of Baghdad, from June 2021 to April 2022. Methods: A total of 200 eyes of 200 individuals were enrolled in this study. CCT and MCT measurements were carried out using spectral-domain optical coherence tomography (Optovue) and a Scheimpflug-Placido topographer (Sirius).The agreement between the two approaches was assessed using Bland-Altman analysis in this study. Results: Mean age was 28.54 ± 6.6 years, mean spherical equivalent of refraction was -3.57 ± 3.35 D. Mean CCT by Optovue, and Sirius were534.13 ± 27.88 μm, and 540.2 ± 27.85μm, respectively.Mean CCT differences between them were -6.070± 6.593 μm, (p &lt; 0.05). Minimum thickness by Optovue was 526.79 ± 27.81, and by Sirius was 537.44 ± 27.56, mean difference between the two devices was 10.66 ± 6.89,p= 0.00. The net power by OCT was 43.44 ± 1.456, mean K by Sirius was 43.597 ± 1.408, with p=0.000. Maximum level of agreement between the two devices is -18.99 to 6.85 for CCT, is widest for minimum thickness -24.166 to 2.85 and narrowest for differences between net corneal power by OCT and mean K By Sirius is -0.87 to 1.18. Conclusion: In clinical practice, the two devices cannot be used interchangeably. CCT and keratometry should be evaluated and followed up using the same device.

Comparison Between Ocular Biometric Parameters and Intraocular Pressure With and Without Contact Lenses.

To compare the values of central corneal thickness, anterior chamber depth (ACD), lens thickness (LT), vitreous length (VL), axial length (AL), and corneal-compensated intraocular pressure performed with and without contact lenses (CL). Forty volunteer participants (16 men and 24 women, 24.2±2.9 years) were recruited. In a single visit, participants underwent autorefraction, keratometry, biometry, topography, pachymetry, and tonometry with the naked eye (without CL). Then, biometry, pachymetry, and tonometry were repeated twice wearing two CL (somofilcon A and nesofilcon A) fitted in a random order. Many of the ocular biometric values were affected by the use of CL during measurements (paired t test; all P ≤0.003), except for LT and VL (Wilcoxon test; both P ≥0.272). Corneal-compensated intraocular pressure was also affected by contact lens wear during measurements, obtaining lower values when wearing them (Wilcoxon test; all P ≤0.001). Central corneal thickness, ACD, AL, and corneal-compensated intraocular pressure measurements cannot be performed while wearing CL. However, LT and VL measurements were not affected by any contact lens use. In addition, it was observed that ACD results from both devices are not interchangeable either when measured with the naked eye or using any contact lens.

Effect of Cycloplegia on Anterior Segment Structures and Scleral Thickness in Emmetropic Eyes.

Purpose: To evaluate the effects of topical cyclopentolate hydrochloride-induced cycloplegia on anterior segment biomechanics in emmetropic eyes using anterior segment-optical coherence tomography (AS-OCT). Methods: Twenty-five emmetropic eyes of 25 volunteers were included. All underwent central corneal thickness (CCT) and anterior chamber depth (ACD) measurements. Anterior scleral thickness (AST) was measured at the level of the scleral spur (SS)(AST-0), 1,000 μm posterior of the SS (AST-1), and 2,000 μm posterior of the SS (AST-2) in the nasal and temporal quadrants using AS-OCT. All measurements were repeated after cycloplegia. Results: The mean age was 30.6 ± 12.4 (8-45) years. The mean CCT did not significantly change after cycloplegia (P = 0.7). The mean ACD was significantly increased [3.3 ± 0.2 (2.7-3.9) to 3.7 ± 0.3 (3-4.2) μm; P = 0.001]. In the nasal quadrant, the mean AST-1 and AST-2 were 512.3 ± 34.4 (433-570) and 529.6 ± 34.2 (449-599); decreased to 478 ± 26.8 (423-530) and 486.2 ± 28.3 (422-544) μm, respectively, after cycloplegia (P = 0.00; P = 0.00). In the temporal quadrant, the mean AST-1 and AST-2 were 522.5 ± 24.7 (473-578) and 527.2 ± 39.9 (450-604); decreased to 481.1 ± 33.7 (421-550) and 484.6 ± 26.6 (433-528) μm, respectively (P = 0.00; P = 0.00). There was no significant difference in AST-0 after cycloplegia in both quadrants [from 697.5 ± 46 (605-785) to 709.5 ± 64.7 (565-785) for nasal and from 718.4 ± 40.1 (632-796) to 722.9 ± 60.6 (596-838) for temporal; P = 0.2; P = 0.3, respectively]. Conclusion: After cycloplegia, there was a significant thinning of ASTs posterior to SS and a slight increase in AST in the SS level. ACD deepened after cycloplegia, and there was no significant change in CCT. Cycloplegic agents temporarily inhibit ciliary muscle contraction and may affect anterior segment parameters and sclera. Inhibition of forward-inward movement of the ciliary body by cycloplegia affects ASTs and ACD by causing a change in the mechanical force of the ciliary muscle on the sclera.

Assessment of the iCare HOME2, a New IOP Self-Measurement Tonometer.

The iCare HOME2 tonometer generally can be considered reliable for most eyes and clinical settings, although it may produce slightly overestimated or underestimated intraocular pressure readings in thicker and thinner corneas, respectively. To evaluate the accuracy, correlation, and analysis of differences in intraocular pressure (IOP) measurements between the gold standard Goldmann applanation tonometer (GAT) and the new, self-measurement iCare HOME2 tonometer (icare, Vantaa, Finland). In this retrospective study, patients were randomly selected from those who attended for a routine examination in our clinic. After a complete ocular examination, each patient's IOP was measured and recorded with GAT (IOPG) and iCare HOME2 (IOPi). Central corneal thickness (CCT) was measured. Eyes with any corneal morbidity were excluded. Pearson's correlation coefficient was used to determine correlation between paired IOP measurements. Bland-Altman plots were graphed for the analysis of differences for IOP between the instruments. One hundred and thirty-five eyes of 70 patients were included in the study. The mean IOPG was 16.3 ±6.5mm Hg (range 3-56). The mean IOPi was 16.5 ±7.3mm Hg (range 3-55), (P=0.47). A strong, significant positive correlation was found for paired IOP measurements by the two instruments (r=0.94; P<0.0001). A small systematic proportional bias was seen for the paired IOP measurements, meaning that with higher IOPs the iCare HOME2 yielded higher IOP readings than GAT; but this difference was clinically insignificant. The instrument underestimated IOPs with corneas thinner than 522 µm while it overestimated IOPs when corneas were thicker than this. The iCare HOME2 could be a reliable tonometer for most eyes and clinical settings. CCT measurement is recommended in patients who use the instrument.

Comparison of the Central Corneal Thickness between a Scheimpflug Imaging-Based Device and an Optical Measurement-Based Device

Background Central corneal thickness is a critical parameter in corneal evaluation for a wide range of purposes in ophthalmology such as refractive surgeries including LASIK, cataract surgeries to assess endothelial pump function preoperatively to preserve the corneal transparency, and glaucoma in terms of diagnosis, management and follow up to avoid over/underestimation of intraocular pressure due to variations in CCT. Aim of the Work The study will investigate the discrepancy in measuring the CCT between Scheimpflug imaging using the Nidek AL-Scan and optical pachymetry using the Nidek Specular Microscope CEM-530. Patients and Methods In our study, we compared CCT measurements of both devices among 70 eyes of 35 normal subjects with a nonsignificant past ocular history. All subjects attended Ophthalmology Department at Ain Shams University Hospitals and all measurements were taken by the same examiner at the same time of the day. Our study is an observational comparative crosssectional study for six months in Ain Shams University Hospitals, Cairo, Egypt after approval of the research ethical committee on normal people without any history of ocular pathology except for refractive errors. Results The mean age of the study subjects was 29.49 ± 7.98 years (range 20-48 years). Regarding age, sex, and refraction, there was no statistically significant difference between CCT measurements by each individual device. However, there was a statistically significant difference between CCT measurements when compared by both devices. The difference between the mean ± SD of both devices was 7.17 ± 0.98 µm. Conclusion There is a statistically significant difference in central corneal thickness measurement between Nidek AL-Scan and Nidek Specular Microscope CEM-530. Several studies are needed to further correlate CCT with other parameters measured by both devices, namely anterior chamber depth and axial length.

Correlation Between Corneal Keratometry, Central Corneal Thickness and Anterior Chamber Depth as Measured by Wavelight OB 820 Biometer and Wavelight Oculyzer II in Preoperative Cataract Surgery Patients.

To compare and correlate corneal keratometry (K), central corneal thickness (CCT), and anterior chamber depth (ACD) using a partial coherence interferometry device and a Scheimpflug camera system device in patients planned for cataract surgery. Comparative cross-sectional study. Place and Duration of the Study: Armed Forces Institute of Ophthalmology, from December 2021 to June 2022. Patients planned for cataract surgery underwent measurement of central corneal thickness (CCT), anterior chamber depth (ACD), and keratometric values (K) by Wavelight OB 820 biometer and Allergo Oculyzer II, preoperatively. Correlation and inter-device agreement were assessed between two devices. There were 115 patients with a mean age of 64.23 ± 9.26 years. All anterior segment parameters showed excellent agreement and high degree of correlation between the two optical devices. Correlation coefficient (r) for central corneal thickness was r = 0.958 (p<0.001) while correlation coefficient for anterior chamber depth was r = 0.965 (p<0.001), r = 0.966 (p<0.001) for flat K, and r = .0969 (p<0.001) for steep keratometry, respectively. Ophthalmic parameters assessed by both devices were comparable and are recommended to be used in the clinical practice of keratorefractive and cataract surgeries interchangeably. ACD, CCT, Keratometry, Cataract, OB 820 biometer, Oculyzer II.

The measurement of Central Corneal Thickness.

We aimed to compare five different devices that measure Central Corneal Thickness. The Central Corneal Thickness (CCT) is an important parameter in ophthalmology. It is involved in the management of various eye conditions such as: glaucoma, keratoconus, contact lens wearing, corneal dystrophies, refractive surgery and keratoplasty. We measured the CCT using OCT, Topographer (TOPO), Ultrasonography Pachymeter (US), Specular Microscope (MS), and Non-contact Tonometer (TONO). In the analysis of the data collected from 59 patients we found the following mean values: US - 554.51 ± 29.849 μm, OCT - 548.73 ± 31.080 μm, TOPO - 553.76 ± 29.845 μm, MS - 564 ± 32.637 μm, and TONO - 538.9 ± 35.657 μm. Our results confirmed the strong correlation between techniques. Abbreviations: OCT = Optical Coherence Tomography, CCT = Central Corneal Thickness, TOPO = Topographer, US = Ultrasonography Pachymeter, MS = Specular Microscope, TONO = Non-contact Tonometer.

Repeatability and agreement of central corneal thickness measurements with a new handheld non-contact pachymeter.

To compare the repeatability of central corneal thickness (CCT) measurements taken with a new handheld pachymeter (Occuity PM1 pachymeter) and to assess its agreement with ultrasound biometry and two commercially available optical biometers in participants with normal eyes. Three consecutive CCT measurements of the right eye of 105 participants with normal corneas were acquired by the PM1 pachymeter, Lenstar LS 900 and Oculus Pentacam HR in a random order. This was followed by three measurements with a handheld ultrasound pachymeter (UP) (Pachmate 2). Repeatability and the repeatability limit were calculated for each device and Bland-Altman limits of agreement (LoA) were determined for the PM1 pachymeter compared to the other devices. The mean CCT (±SD) was 551.04 ± 33.43, 558.62 ± 31.46, 549.41 ± 31.00 and 539.73 ± 29.50 μm for the PM1 pachymeter, UP, Lenstar and Pentacam, respectively. The repeatability limits (expressed as the within subject SD for repeat measurements) were 14.02, 13.68, 4.99 and 9.90 μm, respectively. The closest agreement was between the PM1 and Lenstar (mean difference = -1.63 μm with LoA 10.72 μm below and 13.97 μm above the readings obtained with the Lenstar). The PM1 underestimated CCT compared to UP (mean difference = 7.58 μm, LoA 24.63 μm below and 9.47 μm above UP). The agreement was lowest between the PM1 and Pentacam (mean difference = -11.30 μm, LoA between 4.29 and 26.89 μm). The PM1 pachymeter shows excellent precision for CCT measurements across a range of corneal thicknesses in normal eyes and provides a safe and easy-to-use alternative to ultrasound pachymetry.

A Comparison Between Ultrasound Pachymetry and CASIA2 (Anterior-Segment Optical Coherence Tomography) in the Measurement of Central Corneal Thickness.

Background and objective Due in part to its effect on intraocular pressure (IOP) measurements, the assessment of central corneal thickness (CCT) is recognized as an essential part of the initial glaucoma assessment. The most widely utilized clinical technique to measure CCT is ultrasound pachymetry (USP). In recent years, many dedicated anterior-segment optical coherence tomography scanners (AS-OCTs) have been developed. Previous studies have compared CCT measurements between USP and various AS-OCTs. This study aimed to assess the degree of agreement between USP and CASIA2 (Tomey Corporation, Nagoya, Japan), a second-generation swept-source AS-OCT developed in Japan. Methodology The data on CCT screening measurements of 156 eyes (88 patients)performed over a period of three months, from January to March 2020, on glaucoma patients attending the Royal Hallamshire Hospital (RHH) in Sheffield, UKwere collected retrospectively and statistically analyzed. Results The average age of the 88 patients included in the study was 66 years (range: 20-86 years). Our findingsshow that when compared to CASIA2 measurements, USP measurement of the CCT resulted in significantly thicker values (paired t-test: t=23.15,p<2.2 x 10-16). The average difference between the two methods was 19.98 ±10.78 μm. It is hypothesized that this difference may be duein partto inaccurate probe placement during ultrasound probemeasurement, resulting in thicker CCT values. Conclusion The observed difference may be clinically significant as it could induce clinical discrepancy in terms of perceived glaucoma risk in patients. Therefore, USP and CASIA2 should not be used interchangeably, and clinicians should take into account the significant difference between these methods.

Repeatability of a fully automated swept-source optical coherence tomography biometer and agreement with a low coherence reflectometry biometer

BackgroundTo evaluate the repeatability of a fully automated swept-source optical coherence tomography (SS-OCT) and its agreement with an optical low coherence reflectometry (OLCR) for several biometric parameters.MethodsIn this study, 74 eyes of 74 patients were measured using the Eyestar 900 SS-OCT and Lenstar LS 900 OLCR. Flat keratometry (K1) and steep keratometry (K2), central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), and axial length (AL) were measured three times with each device. The repeatability was analyzed with the intrasubject standard deviation, coefficient of variability (CoV), and coefficient of repeatability (CoR) for each instrument. The agreement between the instruments was evaluated with Bland-Altman analysis.ResultsK1, K2 and CCT CoV values were < 0.2%, < 0.4% and < 0.55%, respectively. Higher CoV values were found for ACD and LT ranging from 0.56% to 1.74%. The lowest CoV values were found for the AL measurements (0.03% and 0.06% for the Eyestar 900 and the Lenstar LS 900, respectively). AL measurements provided the highest repeatability, measured with both CoV and CoR values, and the CCT was the parameter with the lowest repeatability. The CCT and LT measurements were statistically significant between the two biometers (P < 0.001). The interval of the limits of agreement was < 0.6 D for K1 and K2, 15.78 µm for CCT, 0.21 mm for ACD, 0.34 mm for LT, and 0.08 mm for AL.ConclusionsBoth biometers provide repeatable measurements for the different parameters analyzed and can be used interchangeably.

Comparison of Central Corneal Thickness Measurement by Specular Microscopy, Optical Coherence Tomography, Optical Biometry and Ultrasound Pachymetry in Normal Eyes

BACKGROUND&#x0D; Precise central corneal thickness (CCT) measurement is of utmost importance in various corneal diseases and refractive procedures. Various methods are available to measure CCT. But studies comparing CCT measurements with different devices have shown variable results. This study compares the CCT measurements by different devices and Ultrasound Pachymetry (USP).&#x0D; METHODS&#x0D; This prospective study that was conducted from October 2017 to June 2019 included 100 subjects aged more than 18 years and CCT was measured by non-contact specular microscopy (NCSM), spectral domain optical coherence tomography (SD-OCT), optical biometry (OB) and USP in normal eyes. For every patient and with each device, three readings were taken and an average was recorded. The data recorded per protocol was analyzed using Intraclass correlation coefficient and Bland-Altman analysis.&#x0D; RESULTS&#x0D; The mean value of CCT with NCSM, SD-OCT, OB, USP was 528.98±32.18µm, 532.64±30.49µm, 517.47±31.89µm and 533.39±33.44µm, respectively. The intraclass correlation was found to be maximum between NCSM and USP (0.953, p&lt;0.001). The mean paired difference of CCT values with SD-OCT and USP was statistically insignificant (-0.75±14.73, p=1.00) whereas the difference obtained with all other devices was statistically significant.&#x0D; CONCLUSIONS&#x0D; A statistically significant positive correlation (p&lt;0.001) was observed on comparing all the four devices with each other for measurement of CCT. The OCT had the best agreement and also positively correlated with USP. Hence, we conclude that OCT can be an effective alternative to USP for measuring CCT.

Effects of fluorescein on corneal endothelial morphology after fundus fluorescein angiography in patients with diabetic macular edema

Purpose To evaluate the effects of fluorescein dye on corneal endothelial morphology (CEM) after fundus fluorescein angiography (FFA) in patients with diabetic macular edema (DME). Methods In this retrospective study, patients were divided into two groups, nonproliferative diabetic retinopathy (Group-1, NPDR) and proliferative diabetic retinopathy (Group-2, PDR). CEM properties including endothelial cell density (ECD), coefficient of variation of cell area (CV), average cell area (AVG), percentage of hexagonal cells (HEX), and central corneal thickness (CCT) were measured before FFA and at week 1 and month 1 after FFA were collected from patients’ charts. Results The study consisted of 48 patient’s 48 eyes in Group-1 and 50 patient’s 50 eyes in Group-2. In both groups, the mean ECD, CV, AVG, HEX, and CCT measurements at week 1 and month 1 after FFA did not differ statistically from the mean measurements before FFA (p > 0.05). The mean ECD measurements in Group-1 were higher than that in Group-2 and showed statistically significant differences among the groups (p < 0.01 for all). In the Pearson correlation analysis in Group-1, there was no statistically significant relationship between best-corrected visual acuity (BCVA) and (intraocular pressure) IOP values and ECD, AVG, CV, HEX, and CCT measurements (except central macular thickness [CMT] and HEX) before FFA, at week 1 and month 1 after FFA (p > 0.05). In Group-2 there was no statistically significant relationship between BCVA, IOP, and CMT measurements and ECD, AVG, CV, HEX, and CCT measurements before FFA, at week 1 and month 1 after FFA (p > 0.05). Conclusions There is no significant change in CEM after FFA in patients with NPDR and PDR with DME.

Evaluation of scleral thickness in patients with Fuchs endothelial dystrophy.

To evaluate scleral thickness using anterior segment-optical coherence tomography (AS-OCT) in Fuchs endothelial dystrophy (FED) and compare the results with healthy individuals. Thirty-two eyes of 32 patients with FED and 30 eyes of 30 age, gender, spherical equivalent and axial length matched healthy participants were included. All subjects underwent a detailed ophthalmological examination including endothelial cell density and central corneal thickness (CCT) measurements. Scleral thickness was measured by AS-OCT (Swept Source-OCT, Triton,Topcon,Japan) in 4 quadrants (superior, inferior, nasal, temporal) from 6mm posterior to the scleral spur. The mean ages were 62.5 ± 13.2 (33-81) for FED group; 64 ± 8.1 (48-81) for control group. CCT was significantly greater in FED group than in the control group (586.8 ± 33.1 (514-635) vs 545.0 ± 20.7 (503-587), respectively)(p = 0.000). In FED group, mean scleral thickness in the superior, inferior, nasal and temporal quadrants were 434.0 ± 30.6 (371-498), 442.8 ± 27.6 (395-502), 447.7 ± 31.4 (382-502), 443.4 ± 30.3 (386-504) μm, respectively. In control group, the mean scleral thickness in the superior, inferior, nasal and temporal quadrants were 381.3 ± 20.0 (341-436), 383.2 ± 16.0 (352-436), 389.2 ± 21.0 (353-440), 383.2 ± 19.2 (349-440) µm, respectively. The mean scleral thickness was significantly higher in all quadrants in FED group than in control group (p = 0.000). In patients with FED, scleral thickness was significantly higher. FED is a progressive corneal disease that results in the accumulation of extracellular material in the cornea. These findings suggest that the accumulation of extracellular deposits may not be limited to the cornea. Due to their functional similarity and anatomical proximity, sclera may also be affected in FED.