Assessing blink dynamics with non-noticeable method.

PURPOSE: The purpose of the study was to demonstrate the feasibility of blink dynamics with a contactless, non-noticeable method without any visible light being reflected to the participant's eye by the device, and to investigate the blink dynamics parameters in 39 participants whose blink dynamics were examined with this method. It was also aimed to explain the potential of corneal topography devices for non-noticeable blink dynamics and elucidate some tips to device manufacturers to make them practical. METHODS: A one-minute real-time video image in the meibography module of the scheimpflug camera-based corneal topography device was recorded in the slow motion mode of the mobile phone. Detailed analysis of blink dynamics was made by advancing the video images manually at 10 ms intervals. Lid Closing Time (LCT), Lid Opening Time (LOT), third Interblink Interval times (IBI(3)), fifth Interblink Interval times (IBI(5)), Number of Blinks Per Minute (NoB), Number of Complete Blinks Per Minute (NoCB), Number of Incomplete Blinks Per Minute (NoICB) were investigated. RESULTS: The average NoB, NoCB, and NoICB (blinks/minute) with ± standard deviation (SD) values were found to be 22.9 ± 14.4; 14.5 ± 12.4 and 8.4 ± 8, respectively. The average IBI(3) time(seconds) with ± SD was measured as 3.4 ± 4.5. The average IBI(5) time (seconds) with ± SD was 3.9 ± 3.7 The average LCT time (milliseconds) with ± SD was found to be 91.9 ± 36.9 in the 4 different blinks analyzed. The average LOT time (milliseconds) with ± SD was found to be 582.6 ± 196.5 in the 3 different blinks analyzed. CONCLUSIONS: Blink dynamics can be examined in detail with corneal topography devices in a non-contact, no visible light, and most importantly, non-noticeable manner. Existing video imaging modules of corneal topography devices have the potential to investigate blink dynamics. It is anticipated that the clinical use of blink dynamics, which can be performed practically, will increase, particularly in the monitoring of ocular surface and neurological diseases.

Scheimpflug-Based Corneal Biomechanical Analysis As A Predictor of Glaucoma in Eyes With High Myopia.

Purpose: To address if corneal biomechanical behavior has a predictive value for the presence of glaucomatous optical neuropathy in eyes with high myopia. Patients and Methods: This observational cross-sectional study included 209 eyes from 108 consecutive patients, divided into four groups: high myopia and primary open-angle glaucoma (POAG) - HMG, n = 53; high myopia without POAG - HMNG, n = 53; non-myopic with POAG - POAG, n = 50; non-myopic and non-POAG- NMNG, n = 53. Biomechanical assessment was made through a Scheimpflug-camera-based technology. Receiver operating characteristic curves were made for the discrimination between groups. Multivariable logistic regression models were performed to address the predictive value of corneal biomechanics for the presence of glaucoma. Results: Areas Under the Receiver Operating Characteristic (AUROCs) above 0.6 were found in 6 parameters applied to discriminate between HMG and HMNG and six parameters to discriminate between POAG and NMNG. The biomechanical models with the highest power of prediction for the presence of glaucoma included 5 parameters with an AUROC of 0.947 for eyes with high myopia and 6 parameters with an AUROC of 0.857 for non-myopic eyes. In the final model, including all eyes, and adjusted for the presence of high myopia, the highest power of prediction for the presence of glaucoma was achieved including eight biomechanical parameters, with an AUROC of 0.917. Conclusion: Corneal biomechanics demonstrated differences in eyes with glaucoma and mainly in myopic eyes. A biomechanical model based on multivariable logistic regression analysis and adjusted for high myopia was built, with an overall probability of 91.7% for the correct prediction of glaucomatous damage.

Using three-dimensional modelling of the anterior sclera to investigate the scleral profile in myopic eyes.

PURPOSE: This study used three-dimensional (3D) modelling to investigate scleral profiles in myopic eyes and compare them with emmetropic eyes. METHODS: In this prospective observational study, the eyes of 151 participants were analysed using the corneoscleral profile module (CSP) of the Pentacam HR. Non-rotationally symmetrical ellipsoids were fitted to the anterior scleral sagittal height. Three radii were analysed, namely the nasal-temporal (Rx), superior-inferior (Ry) and anterior-posterior (Rz) orientations. Additionally, the area index (AI) and aspherical parameters (Qxy, Qxz and Qyz) of the anterior sclera-fitted ellipsoid (ASFE) were quantified. RESULTS: The findings showed an increase in Rx (-0.349 mm/D), Ry (-0.373 mm/D), Rz (-1.232 mm/D) and AI (-36.165 mm2 /D) with increasing myopia. From emmetropia to high myopia, the vertical and horizontal planes of the anterior sclera became increasingly prolate (emmetropia, Qxz: 0.02, Qyz: 0.01; low myopia, Qxz: -0.28, Qyz: -0.28; high myopia, Qxz: -0.41, Qyz: -0.43). There were no significant differences in the coronal plane across the three groups (H = 2.65, p = 0.27). The anterior scleral shape of high myopes in the horizontal and vertical planes was more prolate than that of emmetropes and low myopes (Qxz, high myopes vs. low myopes: p = 0.03, high myopes vs. emmetropes: p < 0.001; Qyz, high myopes vs. low myopes: p = 0.04, high myopes vs. emmetropes: p < 0.001). CONCLUSIONS: As the degree of myopia increased, non-uniform anterior scleral enlargement was observed. These findings provide a better understanding of the anterior segment with varying degrees of myopia.

Comparison of a New Scheimpflug Camera and Swept-Source Optical Coherence Tomographer for Measurements of Anterior Segment Parameters.

INTRODUCTION: This study evaluated the differences and agreement between a new Scheimpflug camera (Scansys) and a swept-source anterior segment optical coherence tomographer (CASIA 2) for measurements of the anterior segment of the eye in normal subjects. METHODS: This prospective study included 84 eyes from 84 normal adult subjects who underwent three consecutive measurements with the Scansys and the CASIA 2 in random order. The mean keratometry (Km), astigmatism magnitude (AST), J0, and J45 vectors for both anterior and posterior corneal surfaces, central corneal thickness (CCT), thinnest corneal thickness (TCT), and anterior chamber depth (ACD) were obtained by both devices. The difference between these two devices was assessed using paired t test and violin plots. Bland-Altman plots and 95% limits of agreement (LoAs) were used to evaluate agreement. RESULTS: No statistically significant differences between the two devices were found for the anterior AST, anterior J45, and posterior J45 (P > 0.05). The remaining parameters were statistically significant (P ≤ 0.05), but the differences not clinically significant. The violin plots showed that the distribution and probability density of the measured parameters were similar for both devices. Bland-Altman plots revealed high agreement for the measured parameters between the Scansys and CASIA 2, with narrow 95% LoAs. CONCLUSIONS: In terms of assessing parameters for the anterior segment, our study indicated that Scansys and CASIA 2 generally showed significant agreement. The two devices used in this study's assessment of all the parameters can be used interchangeably in refractive analysis.

Detecting True Change in Keratoconus after Intracorneal Ring Segment Implantation.

Confirming the progression of keratoconus is of paramount relevance to providing the appropriate treatment. Real change should be considered consistent over time. It must be greater than the variability of the measurement of the device used to monitor the cornea. The present study aimed to assess the intraobserver repeatability and intersession reproducibility of a Scheimpflug camera in measuring corneal parameters in virgin keratoconus and intrastromal corneal ring segments (ICRS) implantation eyes to discriminate real change from measurement noise. Sixty keratoconus and 30 ICRS eyes were included. Corneal parameters were determined in three consecutive measurements and were repeated 2 weeks later. The precision within the same session for all parameters was better in the keratoconic eyes, with mean repeatability limits 33% narrower (range 13% to 55%) compared with ICRS eyes. Mean reproducibility limits were 16% narrower (range +48% to -45%) compared with ICRS eyes. The cutoff values to consider a real corneal shape change were lower for virgin keratoconic than for ICRS, except for the thinnest corneal thickness and Stage C (ABCD system), which were the opposite. Corneal tomography measurements in ICRS eyes showed worse accuracy than in virgin keratoconus, which should be taken into account by practitioners in patients' follow up.

Comparison of central corneal thickness in healthy eyes using ultrasound pachymetry, non-contact specular microscopy and a high-resolution Scheimpflug camera.

PURPOSE: To compare and analyze the interchangeability in measuring central corneal thickness (CCT) using ultrasonic pachymetry (USP, PACHMATE 2, DGH, Inc, Exton, PA, USA), non-contact specular microscopy (NCSM, CEM-530, Nidek CO, LTD, Gamagori, Japan) and a high-resolution Scheimpflug Camera (Pentacam HR, OCULUS, Wetzlar, Germany). METHODS: An observational, cross-sectional study was performed recruiting 216 volunteers, for a sample size of 216 eyes with no ocular abnormalities other than refractive errors. All subjects underwent pachymetric measurements obtained by USP, NCSM and Pentacam HR. Examinations were performed by the same examiner with USP always following the noncontact examinations. RESULTS: The mean CCT (± SD) was 560.30 ± 38.80 µm, 556.76 ± 36.83 µm and 547.31 ± 35.28 µm for USP, NCSM and Pentacam HR, respectively. The Bland-Altman analysis showed that the highest concordance was found between USP and NCSM, with differences between - 13.18 µm and 20.26 µm. For the differences between measurements obtained with Pentacam HR and USP, the differences at Bland-Altman plot were between - 28.25 and 13.57 µm. The lowest concordance was found for the CCT values measured with Pentacam HR and NCSM, with differences between - 25.67 and 6.86 µm. The intraclass correlation coefficient (ICC) between all pairs of measurements was between 0.979 and 0.987, suggesting that the mean measurements were strongly correlated. CONCLUSION: Measurements obtained with all three devices had high correlation. USP and NCSM were found in good agreement and high concordance, too. The above results indicate that these two devices are interchangeable in clinical practice. Pentacam HR may be a useful alternative for measuring CCT; however, it significantly underestimates CCT and cannot be used interchangeably with the other devices that we studied.

Evaluation of corneal and lens densitometry in children with familial Mediterranean fever.

BACKGROUND: This study aimed to investigate the presence of subclinical inflammation in the eye by examining corneal and lens changes in children with familial Mediterranean fever (FMF) and provide the regulation for follow-up and treatment protocols according to the presence of signs of inflammation. DESIGN: This is a cross-sectional, case-control study. METHODS: Topographic parameters and corneal and lens densitometry of 48 patients with FMF (10.12 ± 3.84 years [range: 5-19 years]) and 33 healthy volunteers (10.94 ± 3.78 years [range: 5-19 years]; p > 0.05) were evaluated with a Scheimpflug camera. For corneal densitometric measurements, the cornea was divided into four concentric radial zones and anterior, central, and posterior layers according to corneal thickness. The mean densitometry value for the crystalline lens was calculated in three zones around the center of the pupil. RESULTS: Corneal light backscattering in all layers and zones of the cornea were similar between the patient and control groups. Lens densitometry values in the three zones did not differ between the two groups (p > 0.05). Maximum lens densitometry values were found to be significantly higher in the patient group (22.14 vs 19.11; p = 0.011). CONCLUSION: Monitoring the cornea and lens density in patients with FMF using Pentacam may help to show the presence of subclinical inflammation and regulate the follow-up and treatment protocols. Larger sample sizes and prospective design studies are needed to reach more conclusive results.

Scheimpflug Camera-Based Technique for Multi-Point Displacement Monitoring of Bridges.

Owing to the limited field of view (FOV) and depth of field (DOF) of a conventional camera, it is quite difficult to employ a single conventional camera to simultaneously measure high-precision displacements at many points on a bridge of dozens or hundreds of meters. Researchers have attempted to obtain a large FOV and wide DOF by a multi-camera system; however, with the growth of the camera number, the cost, complexity and instability of multi-camera systems will increase exponentially. This study proposes a multi-point displacement measurement method for bridges based on a low-cost Scheimpflug camera. The Scheimpflug camera, which meets the Scheimpflug condition, can enlarge the depth of field of the camera without reducing the lens aperture and magnification; thus, when the measurement points are aligned in the depth direction, all points can be clearly observed in a single field of view with a high-power zoom lens. To reduce the impact of camera motions, a motion compensation method applied to the Scheimpflug camera is proposed according to the characteristic that the image plane is not perpendicular to the lens axis in the Scheimpflug camera. Several tests were conducted for performance verification under diverse settings. The results showed that the motion errors in x and y directions were reduced by at least 62% and 92%, respectively, using the proposed method, and the measurements of the camera were highly consistent with LiDAR-based measurements.

Anterior Ocular Biometrics Using Placido-scanning-slit System, Rotating Scheimpflug Tomography, and Swept-source Optical Coherence Tomography.

PURPOSE: To compare anterior biometry measurements using placido-scanning-slit topography, rotating Scheimpflug tomography, and swept-source optical coherence tomography. METHODS: A retrospective review consisted of 80 eyes of 49 participants who underwent anterior chamber depth (ACD), central corneal thickness (CCT), and keratometry examination on the same day. We used placido-scanning-slit topography (ORBscan II), rotating Scheimpflug tomography (Pentacam HR), and swept-source optical coherence tomography (CASIA SS1000). The intraclass correlation coefficients and Bland-Altman plots were used to evaluate the agreement and differences between measurements. RESULTS: The mean ACD values were 2.88 ± 0.43, 2.82 ± 0.50, and 2.68 ± 0.44 mm; and the mean CCT values were 536.96 ± 31.19, 543.79 ± 31.04, and 561.41 ± 32.60 µm; and the mean keratometry (Km) were 43.81 ± 1.69, 43.81 ± 1.77, and 44.65 ± 1.95 diopters; as measured by CASIA SS-1000, Pentacam HR, and ORBscan II, respectively. Among the three devices, ACD was deepest to shallowest in the order of CASIA SS-1000, Pentacam HR, and ORBscan II (p < 0.05). The CCT was thickest to thinnest in the order of ORBscan II, Pentacam HR, and CASIA SS-1000 (p < 0.05). No significant differences in Km values were examined between CASIA SS-1000 and Pentacam HR, whereas ORBscan II overestimated Km with a statistically significant difference compared to the other two devices. CONCLUSIONS: High level of agreement was found between CASIA SS-1000 and Pentacam HR for anterior parameters, including ACD, CCT, and Km, suggesting interchangeability. However, ORBscan II measurements differed considerably with the measurements obtained from the other two devices; therefore, it should not be used interchangeably. However, further studies with repeatability test should be considered in order to elucidate the reliability of each device.

Evaluation of anterior segment structures with Scheimpflug camera in patients undergoing sutureless scleral fixation by modified Yamane technique.

PURPOSE: To evaluate anterior segment parameters in patients undergoing sutureless scleral fixation intraocular lens implantation with the modified Yamane technique (SSF-IOL-MY) by using Scheimpflug camera system. METHODS: Each group of 25 patients was included for aphakia undergoing SSF-IOL-MY and for senile cataract undergoing uneventful phacoemulsification and intraocular lens implantation (Phaco+IOL). Anterior chamber depth (ACD), iridocorneal angle (ICA), anterior chamber volume (ACV) and keratometric values were evaluated by Scheimpflug camera (Sirius, CSO, Italy) system. RESULTS: It was seen that the ACD, ICA and ACV display wider structures in patients with SSF-IOL-MY group compared to Phaco+IOL group. However, the ACD (p = 0.828) and ICA (p = 0.219) have not a statistically significant difference, while ACV (p = 0.007) has a statistically significant difference. In terms of keratometric values of the patients, there was no statistically difference in K1, K2 and Kmax values (p = 0.348, p = 0.106, p =0.269, respectively). Although there was no statistically significant difference between the groups in terms of anterior corneal astigmatism, posterior corneal astigmatism was statistically higher in the Phaco+IOL group (p = 0.192, p = 0.031, respectively). CONCLUSION: SSF-IOL-MY surgery affects anterior segment parameters similar to the Phaco+IOL method, which is the gold standard in cataract surgery. In this surgery, it was approached to the gold standard method in terms of IOL position with the ACD, ACV and ICA values and the results of the corneal incision with the keratometric values.

An objective evaluation of lens transparency after vitrectomy surgery with different intravitreal tamponades.

PURPOSE: To evaluate and compare the effects of different intraocular tamponade agents on lens density after vitrectomy. METHODS: The participating patients were divided into four groups according to the tamponade agent used: a sulfur hexafluoride (SF6) group, a perfluoropropane (C3F8) group, a silicone oil group, and a no tamponade group. Lens density measurements were performed preoperatively and two weeks, one month, and three months postoperatively using a Pentacam HR device with a Scheimpflug camera. The postoperative values were compared with the preoperative baseline values, also the values were compared between the four groups. RESULTS: The study included 82 eyes (82 patients). In the SF6 group, lens density significantly increased in all zones two weeks and one and three months postoperatively (all P < .05). In the C3F8 group, lens density significantly increased in all zones three months postoperatively (all P < .01). In the silicone oil group, the zone 1, zone 2, and average lens density (ALD) value significantly increased one and three months postoperatively (all P < .05). In the no tamponade group, the zone 1, zone 2, and ALD values significantly increased three months postoperatively (all P < .05). There were no significant differences between the four groups in any zone either preoperatively or postoperatively (all P > .05). CONCLUSIONS: Although increases in lens density were observed earlier in the tamponade groups than in the no tamponade group, between the groups over the follow-up period were no differences. We need the development of new surgical methods and materials to prevent post-vitrectomy lens damage in the future.

Agreement between Scheimpflug Camera and the Swept-source Optical Coherence Tomography Measurements in Keratometry and Higher-order Aberrations.

PURPOSE: To evaluate the compatibility of corneal curvature and astigmatism, and higher-order aberrations (HOAs) measured by the Scheimpflug camera Pentacam HR and the swept-source optical coherence tomography ANTERION. METHODS: This prospective study included normal subjects with no ophthalmic history. Steep keratometry (K), flat K, astigmatism and its axis of the anterior and posterior surfaces, total corneal power, and HOAs using the two instruments were compared. To compare the mean values of the measurements, a paired t-test was used. Bland-Altman analysis was applied to assess the agreement between the two devices. RESULTS: Fifty-three eyes of 53 subjects were evaluated. There were statistically significant differences for steep K, astigmatism, and vector J0, J45 in the anterior surface and total corneal power between the two devices (p < 0.05). There were also significant differences in the most of the keratometric values of the posterior corneal surface (p < 0.05) except J0 (p = 0.410). Both devices showed strong positive correlations in steep K, flat K, astigmatism (r > 0.81, p < 0.001) with wide ranges of a 95% limit of agreement. Vectoral components were significantly correlated (r > 0.78, p < 0.001) with narrow 95% limit of agreement, except J45 of the posterior surface (r = 0.39, p = 0.004). In the corneal HOAs, there were statistically significant differences in the vertical coma, horizontal trefoil, spherical aberration, and root mean square of each fifth- and sixth-order Zernike coefficient (p = 0.043, p = 0.041, p < 0.001, p < 0.001, and p < 0.001, respectively). Other HOAs showed moderate to strong positive correlations (r > 0.37, p < 0.05). Most HOAs, except for the horizontal trefoil, showed clinically acceptable agreements. The total root mean square of HOAs was not significantly different between the two devices (p = 0.122). CONCLUSIONS: Most of the keratometric values cannot be used interchangeably. However, the vectoral component of astigmatism showed clinically good agreement. Several HOAs have statistically significant differences; however, almost all HOAs showed acceptable agreements, except for the horizontal trefoil.

The Role of Corneal Biomechanics in the Assessment of Ectasia Susceptibility Before Laser Vision Correction.

PURPOSE: To describe the tomographic and corneal biomechanical status of a sample of eyes excluded from LVC and to present the differences in biomechanical behavior in relation to cutoffs of clinical- and tomography-based screening methods used in clinical practice. PATIENTS AND METHODS: Observational cross-sectional study including 61 eyes from 32 consecutive patients who were excluded from LVC in our department. Clinical and demographic data were collected from the patients' clinical records. Tomographic data was assessed with a Scheimpflug camera (Pentacam, OCULUS®). Ablation depth (µm) and residual stromal bed (µm) were calculated by the WaveLight® EX500 laser system software (Alcon, EUA). The corneal biomechanical assessment was made through ultra-high speed Scheimpflug imaging during noncontact tonometry (Corvis ST, OCULUS®). Several ectasia risk scores were analyzed. RESULTS: Mean age was 31.0±6 years old and mean manifest spherical equivalent was -2.01 ± 2.3D. Belin-Ambrósio deviation index was the tomographic parameter with higher proportion of eyes within the ectasia high risk interval. In the biomechanical assessment, more than 95% of eyes met the criteria for ectasia susceptibility in four of the first generation and in two of the second generation parameters. In a cutoff based comparative analysis, eyes with Kmax ≥45.5 D, eyes with VCOMA <0 and eyes with ARTmax ≤350 presented significantly softer corneal biomechanical behavior. CONCLUSION: The majority of eyes excluded from LVC in the present study met the criteria for ectasia susceptibility in several biomechanical parameters, validating the clinical and tomographic based screening prior to LVC in our center. Differences found in the biomechanical assessment regarding cutoffs used in clinical practice highlight its differential role in characterizing risk profile of these patients. Tomography should not be overlooked and the integration of all data, including treatment-related parameters, can be the future of risk ectasia screening prior LVC.

The use of infrared thermal imaging in tonometry with a Scheimpflug camera.

Infrared thermal imaging is currently used in almost every field of medicine. This paper presents the novel use of thermography in ophthalmology - using a thermal camera to assess correct intraocular pressure measurement depending on the position of the patient's head during non-contact tonometry. For the analysed group of 10 healthy subjects, thermographic images of the face were recorded before and after intraocular pressure testing. Pressure was tested with a non-contact tonometer with a Scheimpflug camera. For the acquired 20: 2D images (thermograms), an analysis of the characteristic areas of the face determined temperature changes of the patient's face in contact with the tonometer frame. Analysis and processing of the acquired thermograms was carried out in MATLAB® with the Image Processing Toolbox. The results clearly showed a decrease in the patient's face temperature where the face was in contact with tonometer supports. Temperature changes in the patient's face provide valuable information about the correct position of their head in the device, which directly translates into measurement quality. Therefore, the analysis of changes in the patient's face temperature both before and after the examination can be a tool for assessing correct patient positioning in the tonometer supports.

Assessment of cataract forming effect of diabetes in young adults by lens densitometer.

PURPOSE: To investigate the effect of the diabetes on cataract formation by Pentacam Scheimpflug topography system. MATERIALS AND METHODS: Thirty diabetic patients and thirty-five healthy control subjects were included in the study. Exclusion criteria were smoking, high refractive error, any systemic disease or drug usage associated with cataract formation and to have diabetic retinopathy. The duration of diabetes and HbA1c level were recorded. A comprehensive ophthalmologic examination was performed in all cases. Pentacam (Oculus, Wetzlar, Germany) three-dimensional lens densitometer module was used to measure density of anterior, nuclear and posterior lens regions. RESULTS: Mean age of group 1 and group 2 was 37.80 ± 5.51 years and 36.51 ± 3.77 years, respectively. There were not any difference between groups in the means of age and sex (P = .271; P = .700). The mean duration of diabetes in group 1 was 4.23 ± 3.71 years (6 months-10 year). The mean HbA1c level was 8.12 ± 2.07% (5.4-12.7%). Anterior, nuclear and posterior mean lens densitometry measurements were significantly higher in group 1 (diabetic group) than group 2 (control group) [(8.90 ± 0.59%; 8.05 ± 0.72% P = < .001), (7.52 ± 0.31%; 7.00 ± 0.59% P = < .001), (7.25 ± 0.31%; 6.90 ± 0.73% P = .006), respectively]. CONCLUSION: Diabetes may have cataractous effect in anterior, nuclear and posterior regions of the lens.

Machine learning helps improve diagnostic ability of subclinical keratoconus using Scheimpflug and OCT imaging modalities.

PURPOSE: To develop an automated classification system using a machine learning classifier to distinguish clinically unaffected eyes in patients with keratoconus from a normal control population based on a combination of Scheimpflug camera images and ultra-high-resolution optical coherence tomography (UHR-OCT) imaging data. METHODS: A total of 121 eyes from 121 participants were classified by 2 cornea experts into 3 groups: normal (50 eyes), with keratoconus (38 eyes) or with subclinical keratoconus (33 eyes). All eyes were imaged with a Scheimpflug camera and UHR-OCT. Corneal morphological features were extracted from the imaging data. A neural network was used to train a model based on these features to distinguish the eyes with subclinical keratoconus from normal eyes. Fisher's score was used to rank the differentiable power of each feature. The receiver operating characteristic (ROC) curves were calculated to obtain the area under the ROC curves (AUCs). RESULTS: The developed classification model used to combine all features from the Scheimpflug camera and UHR-OCT dramatically improved the differentiable power to discriminate between normal eyes and eyes with subclinical keratoconus (AUC = 0.93). The variation in the thickness profile within each individual in the corneal epithelium extracted from UHR-OCT imaging ranked the highest in differentiating eyes with subclinical keratoconus from normal eyes. CONCLUSION: The automated classification system using machine learning based on the combination of Scheimpflug camera data and UHR-OCT imaging data showed excellent performance in discriminating eyes with subclinical keratoconus from normal eyes. The epithelial features extracted from the OCT images were the most valuable in the discrimination process. This classification system has the potential to improve the differentiable power of subclinical keratoconus and the efficiency of keratoconus screening.

Anterior chamber depth measurement before and after photorefractive keratectomy. Comparison between IOLMaster and Pentacam.

BACKGROUND: an accurate measurement of anterior chamber depth (ACD) both in eyes that underwent corneal refractive surgery (CRS) and in eyes that did not, can be crucial, as in case of intraocular lens (IOL) calculation in eyes that need to undergo cataract extraction, or during the evaluation of glaucomatous patients. The aim of this nonrandomized retrospective case series was to measure anterior chamber depth (ACD) before and after photorefractive keratectomy (PRK), comparing a rotating Scheimplfug camera (RSC) and a partial coherence interferometer (PCI). METHODS: 125 right eyes of 125 patients were examined. ACD was measured with RSC and a PCI preoperatively and 1, 3 and 6 months postoperatively. The results were analyzed using Friedman and ANOVA test for repeated measures, Wilcoxon test, Pearson and Bland-Altmann correlation. RESULTS: Both instruments showed an ACD decrease after CRS. The mean preoperative difference in ACD between the two instruments was 0.11 ± 0.11 (range: -0.07 mm to 0.73 mm) (p < 0.05) (r = 0.92). The mean difference in ACD reduction between the two instruments was: 0.08 ± 0.11 (range: -0.35 to 0.39 mm) (p < 0.05, r = 0.93) at 1 month; 0.13 ± 0.11 (range: -0.09 mm to 0.48 mm) (p < 0.05, r = 0.93) at 3 months; 0.14 ± 0.15 (range: -0.16 to 0.82 mm) (p < 0.05) (r = 0.87), at 6 months. CONCLUSIONS: The ACD decrease shown with both instruments suggests the presence of anterior segment remodeling after PRK. RSC measurements were larger than PCI ones, both before and after PRK.

Comparison of radius of anterior lens surface curvature measurements in vivo using the anterior segment optical coherence tomography and Scheimpflug imaging.

BACKGROUND: To assess the radius of anterior lens surface curvature (RAL) measurements with anterior segment optical coherence tomography (AS-OCT) in comparison with Scheimpflug imaging. METHODS: This prospective, cross-sectional study was carried out at Zhongshan Ophthalmic Center, Guangzhou, China. We enrolled 59 eyes, including 30 eyes from 30 cataractous volunteers (59 to 87 years) and 29 eyes from 29 young participants (19 to 49 years). After mydriasis, the RAL was measured automatically by the built-in software in the AS-OCT (CASIA 2). The Scheimpflug images were measured with the build-in caliper tool of the Scheimpflug camera (Pentacam), and RAL were further calculated with the principle of best-fitted circle. Intraobserver and interobserver reproducibility of RAL measurement using Scheimpflug camera were evaluated with limit of agreement (LoA) and intraclass correlation coefficient (ICC). Consistency between RAL measurement of Scheimpflug camera and AS-OCT were assessed with LoA, correlation analysis and linear regression. RESULTS: For all subjects, intraobserver (LoA: -0.25 to 0.23 mm, ICC: 0.996) and interobserver reproducibility (LoA: -0.85 to 0.92 mm, ICC: 0.947) of RAL were good using Scheimpflug imaging. Both AS-OCT and Scheimpflug imaging found that the age-related cataract participants had smaller RAL (P=0.010, P=0.001 respectively). LoA of RAL measurement between AS-OCT and Scheimpflug imaging was -3.83 to -0.79 mm, and the Pearson correlation efficient was 0.909 (P<0.001). The RAL values measured by AS-OCT were significantly greater than that by Scheimpflug camera with a mean difference of 2.31 mm for all participants (P<0.001). The RAL measurement could be converted using the equation: YCASIA 2 =1.155 × XPentacam + 1.060. CONCLUSIONS: Both Scheimpflug camera system with internal caliper tool and the AS-OCT are fast and non-contact tools that could measure RAL successfully. The two measurement results are highly correlated and interchangeable through linear regression equation.

Evaluation of Biomechanically Corrected Intraocular Pressure Measurements in Keratoconus and Forme Fruste Keratoconus.

INTRODUCTION: Although biomechanically corrected intraocular pressure (bIOP) is available, the effectiveness of intraocular pressure (IOP) correction in keratoconus and forme fruste keratoconus (FFK) eyes has not been investigated. OBJECTIVE: Evaluation of bIOP measurements in eyes with keratoconus and FFK. METHODS: Forty-two eyes in 21 patients with keratoconus in one eye and FFK in the fellow eye were examined (KC/FFK group; mean age 24.62 ± 8.6 years; 16 males and 5 females). The control group consisted of 62 eyes in 31 unaffected subjects (mean age 26.26 ± 3.64 years; 15 males and 16 females). The bIOP was determined using a Scheimpflug-based tonometer (Corvis Scheimpflug Technology [Corvis ST®]) after measuring the IOP with a conventional non-contact tonometer (NIOP). The agreement between NIOP and bIOP values was examined using the Bland-Altman plot. The difference between NIOP and bIOP (bIOP correction amount) was compared between keratoconus and FFK eyes. RESULTS: In the control group, there were no significant differences between right and left eyes in both NIOP and bIOP values (p = 0.975 and p = 0.224, respectively). In the KC/FFK group, NIOP values were significantly lower in the keratoconus eyes (9.93 ± 1.96 mm Hg) than in the FFK eyes (12.23 ± 3.03 mm Hg; p = 0.0003). There was no significant difference in bIOP values between the right and left eyes of the KC/FFK group (p = 0.168). The bIOP correction amount was significantly increased in keratoconus eyes (3.58 ± 2.12 mm Hg) compared to in FFK eyes (1.80 ± 3.32 mm Hg; p = 0.011). CONCLUSIONS: For eyes with keratoconus and FFK, the bIOP method is effective to adjust IOP measurements based on corneal biomechanical properties.

Anterior segment parameters in Behçet's patients with ocular involvement.

PURPOSE: To evaluate anterior segment findings in Behçet's disease patients within the ocular involvement inactive period. METHODS: One hundred twenty patients with Behçet uveitis in the inactive period (Behçet's disease group) and 121-age and sex matched healthy subjects (control group) were examined. Anterior segment parameters were assessed by Scheimpflug camera. RESULTS: In Behçet's disease group, the mean age was 39.89 ± 10.16 years, and 55.8% of patients were male; in the control group, the mean age was 38.69 ± 14.08 years, and 56.2% of control subjects were male. Pachymetric measurements of corneal apex (523.84 ± 30.36 µ vs 540.73 ± 27.85 µ, p < 0.001) thinnest point (518.70 ± 30.75 µ vs 537 ± 28.66 µ, p < 0.001), mean corneal volume (57.90 ± 3.39 mm3 vs 59.57 ± 3.37 mm3, p < 0.001) were significantly lower and anterior elevation [5.0 (1.0-34.0) vs 2.0 (1.0-7.0) diopter(D), p < 0.001], posterior elevation [11.0 (1.0-66.0) vs 4.0 (0-22.0) D, p < 0.001)] and corneal astigmatism [1.1 (0-7.1) vs 0.7 (0.1-5.7) D, p = 0.005] were significantly higher in the Behçet's disease group than in control group. No significant difference was found in other anterior segment parameters between the Behçet's disease group and control group. Concurrent keratoconus was detected in two cases (1.7%). A statistically significant correlation was found between the corneal measurements and frequency of uveitis attacks. CONCLUSION: The chronic inflammatory process associated with various proinflammatory cytokines, which play a role in the pathogenesis of keratoconus, may also contribute to a decrease in corneal thickness and corneal volume in Behçet's patients with ocular involvement.