Comparison of Central Corneal Thickness Measurements with Four Different New Devices and Ultrasound Pachymetry.

Objectives: To assess the central corneal thickness (CCT) with 5 different devices, evaluate the repeatability of the devices, and determine the possible relationship between thickness values and sex. Materials and Methods: The study included 308 eyes of 154 patients (76 women, 78 men) between the ages of 18-30 who presented to the Ophthalmology Clinic of Mugla Sitki Koçman University Training and Research Hospital. Autorefractor (Topcon, Japan), ultrasound pachymetry (UP) (Ceniscan, USA), high-resolution Pentacam (Oculus, USA), anterior segment-optical coherence tomography (AS-OCT) (Optovue, USA), and Spectralis AS-OCT (Heidelberg, Germany) measurements were assessed. Results: The mean age of the study participants was 23.2±0.2 years and the mean CCT was 540±14.1 µm, with no statistically significant difference in CCT between sexes (p>0.05). Mean CCT values were 557.0±26.7 µm with the autorefractor, 543.6±32.9 µm with UP, 533.8±30.2 µm with the Oculus Pentacam, 519.8±30.1 µm with Optovue AS-OCT, and 547.5±31.6 µm with Heidelberg AS-OCT. Pairwise comparisons between devices showed that the Optovue AS-OCT gave significantly lower CCT measurements than the autorefractor and Heidelberg AS-OCT device (p=0.027 and p=0.033, respectively). The coefficient of repeatability for autorefractor, UP, high-resolution Pentacam, Optovue AS-OCT, and Heidelberg AS-OCT CCT measurements were 1.51%, 2.46%, 3.72%, 2.57%, and 3.34%, respectively. Conclusion: Measurements made with five different devices showed that CCT was comparable and clinically usable. However, it was determined that the Optovue AS-OCT showed lower CCT values compare to other devices. When compared in terms of repeatability, it was found to be lower in the Pentacam than other devices.

The effect of central corneal thickness on intraocular pressure values using various tonometers in the dog.

OBJECTIVE: To compare intraocular pressure readings from three different tonometers, the Tono-Pen AVIA® (TP), TonoVet® (TV) and TonoVet Plus® (TV+) and to determine how measurements from each tonometer are affected by central corneal thickness (CCT). ANIMALS: Ninety dogs. PROCEDURES: Normal dogs and dogs with ocular disease were selected for study inclusion. Central corneal thickness measurements were gathered with the Pachette 4 ultrasonic pachymeter, and IOP measurements were gathered with the three tonometers in random order. ANOVA or Wilcoxon tests were utilized for overall group comparisons. Linear regression analyses were utilized to determine the association between IOP and CCT. RESULTS: When comparing tonometers to each other, for all dogs, readings from the TV+were significantly different compared to the TV (p = <.0001) and TP (p = <.0001); however, there was no significant difference between the TV and the TP (p = .999). Linear regression did not find any significant correlation between corneal thickness and IOP readings with any tonometer when looking at normal dogs or when including dogs with ocular abnormalities. DISCUSSION: This study did not find a significant correlation between an increase in CCT and increase in IOP reading in any tonometer comparison amongst normal and dogs with ocular abnormalities. The TV+produced consistently and significantly higher readings, but measurements did not exceed the expected IOP range in normal dogs. For consistency, the same tonometer should be used when monitoring IOP over time.

The Interday Repeatability of Parameters for the Assessment of Progressive Disease in Subjects With Less Advanced Keratoconus.

PURPOSE: To evaluate the interday repeatability in the measurement of parameters used for the detection of progression of keratoconus by prediction limits (PL) for single measurements, and the repeatability coefficient (RC) for the mean of replicate measurements. DESIGN: Prospective reliability analysis for cases and control eyes. METHODS: Twenty-five eyes in 25 subjects with KC and 25 eyes in 25 healthy controls were included. Four consecutive measurements were made, 3 days apart, with a Pentacam HR tomographic instrument (denoted the Pentacam) and a Nidek ARK 560-A auto-keratometer (denoted the keratometer). Main outcome measures were the intra- and interday RC of parameters used in the detection of progression of keratoconus. RESULTS: The most repeatable parameter obtained with the Pentacam was the curvature power of the central flat meridian (K1, 0.44 D [RC], -0.55 to 0.60 diopter [D] [PL]), followed by the central steep meridian (K2, 0.72 D [RC], -0.90 to 0.94 D [PL]). The interday repeatability of K1 and K2 was similar when using the keratometer (K1, 0.32 D [RC], -0.66 to 0.57 D [PL], K2, 0.93 D [RC], -1.36 to 1.08 D [PL]). The interday repeatability of the curvature power of the steepest point (Kmax, 0.84 D [RC], -0.90 to 1.11 D [PL]) would benefit from being stratified: RC = 0.44 D and PL = -0.49 to 0.67 D for Kmax < 49.0 D, and RC = 1.08 D and PL = -1.19 to 1.42 D for Kmax ≥ 49.0 D. CONCLUSIONS: The interday repeatability of measurements, single or replicate, in subjects with keratoconus should be considered when diagnosing progressive disease. K1 exhibited the best intraday repeatability. Kmax benefits from being stratified according to disease severity.

Corneal thickness evaluation in healthy eyes: Comparison between two different Scheimpflug devices.

PURPOSE: To evaluate the correlation between corneal thickness (CT) measurements obtained with two Scheimpflug devices, Pentacam HR and Precisio, and to elaborate, if necessary, a regression formula which could make these results comparable. DESIGN: Retrospective, Comparative, Observational study. SETTING: Department of Medicine, Surgery and Dentistry, "Scuola Medica Salernitana" University of Salerno, Italy. METHODS: One hundred twenty four healthy eyes of 124 volunteers (65 males; range: 20-32 years; mean age of 24.8 ± 1.7) were included in this study. CT was measured using Pentacam HR and Precisio in three different points: the pupil center (PC), the corneal apex (CA) and the thinnest point (TP). RESULTS: CT obtained with both devices at the PC, at the CA and at the TP showed a good correlation (r = 0.97, r = 0.97, r = 0.97, respectively), but Pentacam HR measurements were significantly thicker than those provided by Precisio (p < 0.01). The differences between Pentacam HR and Precisio were 21.9 ± 8.8 µm at the PC, 21.9 ± 8.9 µm at the CA, 19.1 ± 9.0 µm at the TP. The calculated regression formulas were: y = 0.9558x + 2.3196 for the PC, y = 0.9519x + 4.5626 for the CA, y = 0.9364x + 15.436 for the TP, where x is the CT measured with Pentacam HR and y is the Precisio measurement. CONCLUSIONS: The findings provided by this study highlight that Precisio measures thinner corneas compared to Pentacam HR. The identified regression formulas could be utilized to make interchangeable the results obtained with these two devices.

Comparison of variables measured with a Scheimpflug device for evaluation of progression and detection of keratoconus.

Keratoconus is a progressive ectatic corneal disorder, which can result in severe visual impairment. The new ABCD keratoconus classification system allows differentiated description of the disease. Aim of the study was to evaluate the components of this novel staging system (ARC, PRC, thinnest pachymetry) as well as topometric indices, deviation of normality indices, and other parameters in terms of repeatability and reliability. 317 eyes with keratoconus were examined twice with a Scheimpflug device (Pentacam, Oculus). Bland Altman analysis and intraclass correlations were carried out to evaluate the parameters repeatability and reliability. Apart from IHA (ICC = 0.730), all parameters showed excellent reliability (ICC > 0.900). ARC, PRC, thinnest pachymetry, Kmax, CKI, KI, Rmin, and Progression Avg were the best repeatable parameters with relative repeatability values < 2.5%. Other parameters performing well in terms of repeatability were IHD, ISV, IVA, and final D (RR < 13%). Regression analysis revealed consistently high repeatability along all stages of keratoconus for PRC, thinnest pachymetry, and CKI. All parameters of the ABCD staging system showed excellent reliability and repeatability, PRC and thinnest pachymetry even at all stages of keratoconus and can consequently be reliably used in the determination of keratoconus progression.

The architecture of corneal stromal striae on optical coherence tomography and histology in an animal model and in humans.

The purpose of this study was to use a portable optical coherence tomography (OCT) for characterization of corneal stromal striae (CSS) in an ovine animal model and human corneas with histological correlation, in order to evaluate their architectural pattern by image analysis. Forty-six eyes from female adult sheep (older than 2 years), and 12 human corneas, were included in our study. The eyes were examined in situ by a portable OCT, without enucleation. All OCT scans were performed immediately after death, and then the eyes were delivered to a qualified histology laboratory. In the ovine animal model, CSS were detected with OCT in 89.1% (41/46) of individual scans and in 93.4% (43/46) of histological slices. In human corneas, CSS were found in 58.3% (7/12) of cases. In both corneal types, CSS appeared as "V"- or "X"-shaped structures, with very similar angle values of 70.8° ± 4° on OCT images and 71° ± 4° on histological slices (p ≤ 0.01). Data analysis demonstrated an excellent degree of reproducibility and inter-rater reliability of measurements (p < 0.001). The present study demonstrated that by using a portable OCT device, CSS can be visualized in ovine and human corneas. This finding suggests their generalized presence in various mammals. The frequent observation, close to 60%, of such collagen texture in the corneal stroma, similar to a 'truss bridge' design, permits to presume that it plays an important structural role, aimed to distribute tensile and compressive forces in various directions, conferring resilience properties to the cornea.

Pachymeter Use and Disinfection Practice in the United Kingdom: A National Survey.

OBJECTIVE: Pachymetry plays a crucial role in the diagnosis and management of glaucoma and corneal diseases. There have been several outbreaks of epidemic ocular infections in ophthalmology clinics worldwide with reports of viral, parasitic, and prion disease. Contact pachymetry is a possible vehicle of transmission due to its risk of contamination. We aim to identify the types of pachymetry used and methods employed for cleaning and disinfection in eye units throughout the United Kingdom. METHODS: A telephone survey was carried out, and a senior nurse or sister questioned based on the proforma created. A follow-up email was sent to units that did not respond with the questionnaire attached. RESULTS: Of 109 responses, 10 eye units were unaware of the device name and 4 were unaware of the cleaning method used. Overall, 69/105 (66%) were cleaned with some form of alcohol wipe between patients, 12/105 (11%) used presept solution to soak the pachymetry head mainly 5 to 10 minutes, with 2 units soaking for 20 to 30 minutes. Milton solution was used by 4 units (4%) (10 s to 10 min). Three used a hydrogen peroxide solution for 10 minutes (3%). Three (3%) used an alcohol solution. Fifteen (14%) units used some chlorine-based solution (actichlor/chloraprep) for 5 to 10 minutes. Two (2%) units combined an alcohol-based wipe with solution to soak afterward. CONCLUSIONS: There is a large variation in methods and duration of tip disinfection with only a few units following the Royal College of Ophthalmologists (RCOphth) guidelines on pachymeter disinfection. The majority of eye units use alcohol/chlorine-based wipes for cleaning the pachymetry heads which is against the current recommended guidelines. The average immersion time when solutions were used was 5 to 10 minutes.

Comparison of corneal thickness in patients with dry eye disease using the Pentacam rotating Scheimpflug camera and anterior segment optical coherence tomography.

The purpose of this study was to compare central corneal thickness, thinnest corneal thickness, and the thinnest point of the cornea between Pentacam and anterior segment optical coherence tomography (ASOCT) in patients with dry eye disease (DED). This cross-sectional study included 195 participants between November 2015-June 2017. DED was diagnosed using the Asia Dry Eye Society criteria and further divided into mild and severe DED based on kerato-conjunctival vital staining. Central corneal thickness, thinnest corneal thickness, and the thinnest point of the cornea measured by Pentacam and ASOCT were compared, and Pearson's correlation coefficients were estimated. The differences in central corneal thickness and the thinnest corneal thickness between Pentacam and ASOCT were analysed using Bland-Altman and multivariate regression analyses adjusted for age and sex. This study included 70 non-DED subjects and 52 patients with mild and 73 with severe DED. The Pentacam and ASOCT measurements of central corneal thickness and thinnest corneal thickness were strongly correlated, but the respective values were higher when measured with Pentacam. The Bland-Altman analysis revealed differences in central corneal thickness (non DED, 11.8; mild DED, 13.2; severe DED, 19.6) and in thinnest corneal thickness (non DED, 13.1; mild DED, 13.4; severe DED, 20.7). After adjusting for age and sex, the differences in central corneal thickness (ß = 7.029 µm, 95%CI 2.528-11.530) and thinnest corneal thickness (ß = 6.958 µm, 95%CI 0.037-13.879) were significantly increased in the severe-DED group. The distribution of the thinnest point of the cornea in the cornea's inferior temporal quadrant between Pentacam and ASOCT deviated in severe DED (Pentacam: 90.4% vs. ASOCT: 83.6%). Clinicians should consider that there were significant differences in corneal-morphology assessment between the measurements with Pentacam and ASOCT in severe DED.

Comparison of corneal elevation and pachymetry measurements made by two state of the art corneal tomographers with different measurement principles.

PURPOSE: To compare corneal tomography measurements (elevation and pachymetry) as made by two corneal tomographers: Pentacam AXL and CASIA 2. MATERIAL AND METHODS: The devices were used in a standard measuring mode. 77 normal eyes were measured five times with both devices. The data maps for anterior and posterior corneal elevation and pachymetry were exported and analyzed. Repeatability and average values were calculated for each valid data point on the exported data maps. We also calculated a corrected repeatability of the elevation data maps by removing rotation, tilt, and decentration through realignment of the elevation measurement of each eye prior to analyzing the variations in the measurement usingthe same method as for the repeatability. RESULTS: Pentacam AXL offered the better (corrected) repeatability for anterior corneal elevation measurements. CASIA 2 offered better repeatability for the pachymetry measurements. The tomographers could not be used interchangeably. The central corneal thickness was measured 9 µm ± 3 µm larger when measured with Pentacam AXL compared to CASIA 2.

Variability of Central Corneal Thickness Measurements-Comparing Zeiss IOL Master and Tomey Corneal Specular Microscope.

PURPOSE: The aim of this study was to compare the intraobserver repeatability and agreement of central corneal thickness (CCT) measurements by 2 commonly available instruments, Zeiss IOL Master 700 (SS-OCT-based optical biometry device) and Tomey corneal specular microscope EM-3000 (Noncontact specular microscopy). DESIGN: Retrospective study. METHODS: This is a retrospective analysis of data from routine clinical practice in which preoperative CCT measurements of 105 patients scheduled for cataract surgery were analyzed. Two consecutive CCT measurements were measured using Zeiss IOL Master 700 and Tomey corneal specular microscope EM-3000 by the same examiner. The repeatability of CCT measurements was analyzed by mean intraobserver difference, coefficient of repeatability (CR), and intraclass correlation. The agreement between the 2 methods was analyzed by mean difference and limits of agreement (LoA) using the Bland-Altman method. RESULTS: The mean absolute intraobserver difference between the 2 measurements by Zeiss and Tomey were 3.41 ±â€Š3.98 µm and 8.62 ±â€Š9.52 µm (P < 0.0001), respectively. For Zeiss, the CR was 10.3 µm with 95% LoA of -10.5 to 10.1 µm. For Tomey, the CR was 25.2 µm with 95% LoA of -25.2 to 25.2 µm. The mean CCT measurements ±â€Šstandard deviation by Zeiss and Tomey were 544.0 ±â€Š38.1 µm and 532.6 ±â€Š40.0 µm, respectively (P = 0.003). The 95% LoA in CCT between the 2 methods was -15.8 to 38.7 µm. CONCLUSIONS: Zeiss IOL Master 700 has superior intraobserver repeatability and consistency than Tomey EM-3000. Zeiss produced higher CCT measurements than Tomey; hence, in clinical practice, interchangeability between these 2 methods is limited.

Dynamic Scheimpflug Ocular Biomechanical Parameters in Healthy and Medically Controlled Glaucoma Eyes.

PURPOSE: To evaluate the relationship between biomechanical parameters measured with a dynamic Scheimpflug analyzer and glaucoma. PATIENTS AND METHODS: Cross-sectional observational data of 47 eyes of 47 consecutive subjects with medically controlled primary open-angle glaucoma and 75 eyes of 75 healthy subjects examined with a dynamic Scheimpflug analyzer (Corvis ST) were retrospectively investigated. Eight biomechanical parameters were compared between eyes with and without glaucoma using multivariable models adjusting for intraocular pressure (IOP), central corneal thickness, age, and axial length. RESULTS: In multivariable models, glaucoma was negatively correlated with A1 time (P<0.001, coefficient=-0.5535), A2 time (P=0.008, coefficient=-0.1509), radius (P=0.011, coefficient=-0.4034), and whole eye movement (P<0.001, coefficient=-0.0622). Negative correlation between glaucoma and 3 parameters (A1 time, A2 time, and radius) consistently indicate larger deformability of the cornea and negative correlation between glaucoma and whole eye movement indicate smaller eye movement, in glaucoma eyes. There were significant correlations of many biomechanical parameters with other baseline factors (8 parameters with IOP, 2 with central corneal thickness, 4 with age, and 7 with axial length). CONCLUSIONS: Eyes with medically controlled glaucoma were more deformable than healthy eyes, which may increase the risk of optic nerve damage through an underestimation of IOP and biomechanical vulnerability of the globe. Many parameters showed a significant correlation with baseline factors, suggesting the importance of adjustment for these confounding factors when evaluating the correlation between biomechanical parameters and ocular diseases. These results suggest the relevance of measuring biomechanical properties of glaucoma eyes for accurate IOP measurement and risk assessment.

Agreement of post-LASIK corneal power and corneal thickness measurements by pentacam and GALILEI corneal tomography systems.

BACKGROUND: Post-LASIK corneal conditions cannot be accurately measured by traditional optometric approaches. Therefore, we aimed to analyze the agreement of two rotating Scheimpflug cameras in corneal assessment. METHODS: Fifty otherwise healthy volunteers who had undergone LASIK were recruited in this study. The values of mean and central total corneal power (TCP), including TCP1, TCP2, and TCP-IOL, were measured by GALILEI Scheimpflug camera. The values of total corneal refractive power (TCRP) readings at both 2 mm ring and 3 and 4 mm zones were detected by Pentacam Scheimpflug camera. Central corneal thickness (CCT) and thinnest corneal thickness (TCT) were quantified by GALILEI and Pentacam respectively. Paired t-tests and Bland-Altman analyses were used to evaluate statistical differences between measurement results obtained by GALILEI and by Pentacam. RESULTS: Among these 50 subjects, the mean and central TCP1 values (37.31 ± 2.61 and 37.27 ± 2.64) derived from GALILEI measurements were consistent with the TCRP values (37.08 ± 2.76, 37.11 ± 2.74, and 37.19 ± 2.68; p > 0.05) determined by Pentacam at the 2 mm ring apex, 3 mm zone apex, and 4 mm zone apex. There were no statistically significant differences in central corneal thickness (CCT) values measured by the two cameras (463.64 ± 55.67 µm for GALILEI and 470.69 ± 44.04 µm for Pentacam, respectively; p > 0.05). However, the limits of agreement were wide when comparing mean TCP1 (-1.4 to 1.8 D, -1.4 to 1.8 D, and -1.3 to 1.6 D), central TCP1 (-1.2 to 1.6 D, -1.2 to 1.6 D, and -1.2 to 1.4 D) and CCT (-77.2-63.0 µm). CONCLUSION: Corneal power and corneal thickness are disparate post-LASIK evaluation parameters when comparing the utility of GALILEI with that of Pentacam.

Correcting astigmatism at the time of cataract surgery: Toric IOLs and corneal relaxing incisions planned with an image-guidance system and intraoperative aberrometer versus manual planning and surgery.

PURPOSE: To compare the outcomes of the combination of an image-guided system and intraoperative aberrometer with the surgeon's standard of care in correcting astigmatism using toric intraocular lenses (IOLs) or corneal incisions. SETTING: Single site in United States. DESIGN: Prospective case series. METHODS: Contralateral eyes of patients having uncomplicated bilateral cataract surgery and astigmatism correction were randomly assigned to Group A or Group B. Group A received the surgeon's preferred standard of care. Group B had preoperative planning using an image-guidance system (VERION), intraoperative aberrometry (ORA System with VerifEye+), and femtosecond laser-assisted cataract surgery. The primary endpoint was the residual refractive astigmatism at 3 months. RESULTS: Thirty-eight eyes were treated with toric IOLs and 40 eyes with corneal astigmatic incisions. On average, toric IOLs resulted in almost 0.25 diopter (D) less cylinder than corneal astigmatic incisions (P < .01), with no difference between groups (P = .41). There was no statistically significant difference in the mean spherical equivalent refraction by group (P = .51). At 3 months, the IOL in 4 eyes (11%) (2 in Group A and Group B each) was more than 10 degrees of absolute orientation from the intended orientation. The mean keratometry was 0.16 D higher with the image-guided system compared with optical biometry (Lenstar). The vector difference between the 2 measurements was 0.5 D or lower in all eyes. CONCLUSIONS: The combined use of an image-guided system and intraoperative aberrometer did not significantly improve outcomes compared with the surgeon's standard of care. Based on keratometry, there was good agreement in corneal astigmatism measurements between the image-guided system and the optical biometer.

Comparison of central corneal thickness measurements using different imaging devices and ultrasound pachymetry.

PURPOSE: To compare central corneal thickness (CCT) measurements obtained by the AL-Scan, Lenstar LS900, Galilei, and ultrasound pachymetry (UP) in normal and cataractous eyes. METHODS: Eighty eyes of healthy subjects were included in the study. Each subject was assessed by four different methods of measurements using the AL-Scan, Lenstar LS900, Galilei, and UP by a single examiner. To assess the intraobserver repeatability, three consecutive measurements were taken for the AL-Scan. RESULTS: The mean CCT [± standard deviation (SD)] for the AL-Scan, Lenstar LS900, Galilei, and UP were 554.6 ± 30.9 µm, 542.9 ± 31.3 µm, 570.7 ± 30 µm, and 552.7 ± 32.8 µm, respectively. The differences between pairs of mean CCT for the methods are statistically significant for the pairs of Galilei-UP, AL-Scan-Galilei, and Lenstar LS900-Galilei. Bland-Altman plots showed that AL-Scan-UP have the closest agreement, followed by Lenstar-UP and AL-Scan-Lenstar. Galilei was found to have the poorest agreement with the other three methods. The intraobserver repeatability of the AL-Scan was very good with an intraclass correlation coefficient (ICC) of 0.980. CONCLUSION: We found that CCT measurements between the AL-Scan-UP, Lenstar LS900-UP, and AL-Scan-Lenstar LS900 showed very strong correlation and comparable agreement. AL-Scan-UP showed the closest agreement and these devices can be used interchangeably in clinical practice. Galilei significantly showed higher value of CCT compared to other methods. It was also observed that the Al-Scan had excellent intraobserver repeatability.

Comparison of central corneal thickness measurements with standard ultrasonic pachymetry and optical devices.

BACKGROUND: To compare the repeatability and agreements of central corneal thickness measurements of healthy individuals obtained by Scheimpflug-Placido topographer (Sirius), anterior segment spectral domain optical coherence tomography (Spectralis) (AS-OCT), optical biometry (AL-Scan) and ultrasonic pachymetry. METHODS: Sixty-four eyes of 32 subjects with no ocular or systemic diseases were included in this study. Central corneal thickness measurements performed with Sirius, AS-OCT, optical biometry AL-Scan and ultrasonic pachymetry were compared. Bland-Altman analysis was used to demonstrate agreement between methods. Intra-examiner repeatability was assessed by using intraclass correlation co-efficients (ICCs). RESULTS: Sixty-four eyes of 32 patients were enrolled (25 male and seven female). The mean age was 23.8 years (range 21-28 years). The mean central corneal thickness was 560.8 ± 37.2 µm, 528.8 ± 32.0 µm, 546.4 ± 33.8 µm, 543.4 ± 35.8 µm for the ultrasonic pachymetry, optical biometry AL-Scan, Sirius and AS-OCT values, respectively. The thickest mean central corneal thickness (560.8 ± 37.2 µm) was obtained from ultrasonic pachymetry. The thinnest mean central corneal thickness (528.8 ± 32.0 µm) was obtained from optical biometry AL-Scan. All four modalities of central corneal thickness measurements correlated closely with each other. Intra-examiner repeatability was excellent for all devices with ICCs > 0.90. CONCLUSIONS: In conclusion, although measurements obtained by various methods correlate well, the measurements are not directly interchangeable. Between ultrasonic pachymetry and the three optical instruments tested, significant diferences can be seen. Therefore, the same imaging method should be used in corneal thickness follow-ups.

Normative Pentacam anterior and posterior corneal elevation measurements: effects of age, sex, axial length and white-to-white.

PURPOSE: To provide normal corneal elevation data for a large Caucasian population and to determine the impacts on these data of age, sex, axial length (AXL) and horizontal white-to-white (WW). SETTING: Centro Internacional de Oftalmología Avanzada, Madrid, Spain. DESIGN: Retrospective, cross-sectional, observational. METHODS: In this retrospective, cross-sectional, observational study, anterior and posterior corneal elevations were measured in 789 right eyes of subjects with no ocular disease at the thinnest corneal location in relation to a fixed 8-mm best-fit sphere using the Pentacam, and AXL and WW were measured with the IOLMaster. A multiple linear regression model was used to assess the effects of age, sex, AXL and WW on the elevation data. RESULTS: Mean subject age was 50.5 ± 15 years (range 17-93 years); 64% were women. Mean anterior and posterior corneal elevations were 1.99 ± 1.75 µm (- 7 to 10 µm) and 7.70 ± 5.7 µm (- 6 to 28 µm). Anterior corneal elevations were higher by 0.165 µm and 0.033 µm for every mm reduction in AXL and every year reduction in age, respectively. Sex and WW were not significant predictors of anterior elevations (R2 = 7.7%). Posterior corneal elevation increased by 0.186 µm/year of age, 0.707 µm/mm reduction in WW and 0.819 µm/mm reduction in AXL. This variable was also 0.866 µm greater in men (R2 = 34.4%). CONCLUSION: Anterior corneal elevations decrease with age and are higher for shorter AXL but are not influenced by sex or WW. Posterior corneal elevations increase with age, decreasing AXL, decreasing WW and are higher in men.

Agreement and repeatability of central corneal thickness measurements by four different optical devices and an ultrasound pachymeter.

PURPOSE: To compare the repeatability and agreement of central corneal thickness (CCT) measurements by spectral-domain optical coherence tomography (OCT), corneal topography (CT) with a combined Scheimpflug-Placido system, optical biometry (OB), specular microscopy (SM), and ultrasound pachymetry (UP). METHODS: A single observer measured CCT twice in 150 eyes of 150 subjects with each of five devices: Nidek RS-3000 Advance OCT, CSO Sirius combined Scheimpflug-Placido disc system CT, Nidek AL-Scan partial coherence interferometry-based OB, Tomey EM-3000 SM, and Reichert iPac ultrasonic pachymeter. Pachymetry values corrected by the SM device software were also recorded. Levels of agreement between devices were evaluated by Bland-Altman plots with 95% limits of agreement, and repeatability for each device was analysed with intraclass correlation coefficients. RESULTS: The mean CCTs measured by OCT, CT, OB, SM, corrected SM, and UP were 544.60 ± 29.56, 536.19 ± 32.14, 528.29 ± 29.45, 524.88 ± 32.38, 537.88 ± 32.38, and 545.29 ± 30.75 µm, respectively. Mean CCT differed significantly between the devices (p < 0.05) apart from between OCT and UP, and between CT and corrected SM. Mean paired differences between devices ranged between 0.68 and 20.41 µm. Repeatability with all devices was excellent (> 0.99). The range of limits of agreement was the least between OCT and UP. CONCLUSIONS: Different CCT measurement techniques produce quite different results, so CCT evaluation and follow-up should be performed using the same device or devices with close compatibility.

Agreement and Repeatability of Two Biometers to Measure Anterior Segment Components: Refractive Error Effect.

BACKGROUND To assess the repeatability and agreement between a new high-resolution optical coherence tomographer (OCT) and a Scheimpflug topographer. MATERIAL AND METHODS Sixty phakic and healthy participants were measured in this study, and one eye per participant was analyzed. Depending on their refractive error, each participant was allocated into a myopic, hyperopic, or emmetropic group. The Cirrus HD-OCT 5000 (Carl Zeiss Meditec, Jena, Germany), and the Sirius Scheimpflug topographer (Costruzione Strumenti Oftalmici, Florence, Italy) were used to take all measurements. RESULTS The repeatability of these instruments to measure the anterior chamber depth, angle-to-angle, thinnest pachymetry, and both nasal and temporal angles was smaller than 0.15 mm, 0.40 mm, 10 µm, and 10 degrees, respectively. However, the repeatability of the Scheimpflug instrument to measure the apex pachymetry was about 15 µm, and for the OCT, it was about 4 µm for all groups. On average, the Sirius Scheimpflug instrument measured shallower anterior chamber depth (about 0.10 mm), shorter angle-to-angle (about 0.5 mm), thinner corneas (approximately 10 µm), and narrower angles (around 5 degrees) for all refractive groups. CONCLUSIONS The repeatability of the Cirrus OCT and Sirius Scheimpflug instrument was good and independent of the refractive error. Nevertheless, to judge whether these instruments could be used interchangeable, clinical criteria are needed.

Interdevice variability of central corneal thickness measurement.

PURPOSE: To evaluate variability of central corneal thickness measurement (CCT) devices using a hitherto unprecedented number of CCT devices. METHODS: CCT was measured consecutively in 122 normal corneas of 61 subjects with seven different devices using three distinct measurement technologies: Scheimpflug, Ultrasound, and Optical Coherence Tomography (OCT). Per device deviation from the mean CCT value per eye was used to determine which of the devices performed best, compared to the mean value. RESULTS: Cirrus OCT yielded the lowest deviation. Deviations of the individual devices from the mean CCT of each eye were (OS/OD) 12.8±5.0/14.9±9.4 µm for Topcon noncontact specular microscopy (NCSM), 11.3±5.9/10.6±7.3 µm for Pentacam, 10.7±5.2/10.4±4.8 µm for Spectralis OCT, 6.0±3.9/6.2±4.9 µm for Topcon DRI OCT, 5.1±3.4/5.9±10.3 µm for AngioVue OCT, 4.8±4.1/5.7±4.6 µm for US pachymetry, and 4.2±3.2/5.7±4.6 µm for Cirrus OCT. The maximum differences between US pachymetry and the other devices were very high (up to 120 µm). CONCLUSION: Central corneal thickness may be under- or overestimated due to high interdevice variations. Measuring CCT with one device only may lead to inappropriate clinical and surgical recommendations. OCT showed superior results.

Accuracy of Cirrus HD-OCT and Topcon SP-3000P for measuring central corneal thickness / Precisión de Cirrus HD-OCT y Topcon SP-3000P en la medición del espesor corneal central

Purpose: To compare and analyze the interchangeability of three measuring systems, each based on a different technique, for central corneal thickness (CCT) analysis. Methods: CCT measurements were measured using optical coherence tomography (OCT), non-contact specular microscopy (NCSM), and ultrasonic pachymetry (USP) in 60 eyes of 60 healthy patients with a mean age of 66.5 ± 15.0 years and a mean spherical equivalent of 0.43 ± 1.14 D. Analysis of variations in measurement concordance and correlation among the three different methods were performed. Comparison of CCT measurements were done using Bland-Altman plots (with bias and 95% confidence intervals), intraclass correlation coefficient (ICC), and paired t-student analysis. Results: Mean CCT values were: 549.20 ± 26.91μm for USP (range 503-618μm), 514.20 ± 27.49μm for NCSM (range 456-586μm) and 542.80±25.56μm for OCT (range 48-605μm). CCT values obtained with NCMS were significantly lower than those obtained with OCT and USP methods. NCMS CCT value was 36.08 ± 10.72μm lower than USP value (p < 0.05), and NCMS CCT value was 7.88 ± 8.86 μm lower than OCT value (p < 0.05). ICC between USP-NCSM pair was 0.488 and 0.909 between USP-OCT pair. Conclusion: OCT and UPS offered highly comparable results, whereas NCSM offered lower mean CCT values compared to the other two methods. Therefore, NCSM should not be considered a reliable method for measuring CCT and should rather be considered for assessing longitudinal changes in the same patient

Objetivo: Comparar y analizar la intercambiabilidad de tres sistemas de medición, basado cada uno de ellos en una técnica diferente, para estudiar el espesor corneal central (ECC). Métodos: Se realizaron mediciones del ECC utilizando tomografía de coherencia óptica (OCT), microscopía especular (NCSM), y paquimetría ultrasónica (USP) en 60 ojos de 60 pacientes sanos, con una edad media de 66,5 ± 15 años y un equivalente esférico medio de 0,43 ± 1,14 D. Se realizaron análisis de las variaciones de concordancia de las mediciones, y correlación entre los tres métodos diferentes. Se compararon las mediciones del EEC utilizando gráficos de Bland-Altman (con desviaciones, e intervalos de confianza del 95%), coeficiente de correlación intra-clase (ICC), y análisis de t pareada de Student. Resultados: Los valores medios de ECC fueron: 549,2 ± 26,91μm para USP (rango 503-618 μm), 514,2 ± 27,49μm para NCSM (rango 456-586 μm) y 542,8 ± 25,56 μm para OCT (rango 486-605 μm). Los valores de ECC obtenidos con NCMS fueron significativamente inferiores que los obtenidos con los métodos OCT y USP. El valor de ECC obtenido mediante NCMS fue inferior en 36,08±10,72μm al valor obtenido mediante USP (p < 0,05), y el valor de ECC obtenido mediante NCMS fue inferior en 7,88 ± 8,86 μm al obtenido mediante OCT (p < 0,05). El ICC entre el par USP-NCSM fue de 0,488, y de 0,909 entre el par USP-OCT. Conclusión: Los métodos OCT y UPS aportaron resultados altamente comparables, mientras que NCSM aportó unos valores medios de ECC inferiores a los aportados por los otros dos métodos. Por tanto, NCSM no debería considerarse un método fiable en la medición del ECC, debiéndose utilizar en la valoración de los cambios longitudinales del mismo paciente