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Background: To determine if cross‐linking (CXL) treatment modifies any pre‐existing association between corneal optical density (COD) and age in keratoconus free of corneal scarring. Methods: COD was monitored in two groups (i) before and after standard CXL treatment for keratoconus (de‐epithelization with a crescent blade, n = 69 eyes) and (ii) age/gender‐matched cases without any signs of keratoconus (n = 24 eyes). Seven different markers of COD were quantified using a 0–100 grey scale, supplied with Pentacam™ software. Results: Mean age (±sd, range) in Group I (19 females and 50 males) was 24.2 years (±7.2, 11–44) and in Group II (9 females and 15 males), it was 24.7 years (±7.6, 17–45). COD over the apex and along the depth of the cornea (y, arbitrary scale units) was associated with age (x, in years) in Group I at preop (y = 0.08x + 13.12, rs = 0.350 and p = 0.003), at 12 months postop (y = 0.08x + 15.15, rs = 0.295 and p = 0.014) and in Group II, at the start (y = 0.16x + 11.28, rs = 0.474 and p = 0.019) and 12 months later (y = 0.24x + 8.63, rs = 0.600 and p = 0.002). The change in COD following CXL was significantly associated with the preop value. Conclusion: CXL initially breaks down the pre‐existing relationship between COD and age. This is re‐established by 12 months postop. The CXL induced change in COD depends on the preop value but not on the patient's age. [ABSTRACT FROM AUTHOR]

Keratoconus (KC) is an irreversible blinding eye disease; therefore, early screening of KC suspects (KCS) is crucial for protecting patients' quality of life. Scheimpflug imaging is a commonly used screening device in clinical practice. We aimed to evaluate the diagnostic ability of a Scheimpflug imaging device (Scansys) for KC and KCS and compared it with other Scheimpflug-based devices (Pentacam and Corvis ST). This prospective case-control study included 107 normal eyes, 72 KCS, and 57 KC. Scansys screening index Keratoconus probability (KCP) showed excellent performance in diagnosing KC at a cutoff value of 16.4 (area under the receiver operating characteristic [AUROC] = 1.000), with 100% sensitivity and 98.11% specificity. KCP had a better KCS diagnostic ability at a cutoff value of 8.9 (AUROC = 0.813) than Corvis biomechanical index (CBI, AUROC = 0.764), reaching 67.61% sensitivity and 85.85% specificity. Pentacam screening index Belin/Ambrósio enhanced ectasia display deviation (BAD-D) showed the best performance with 92.96% sensitivity and 89.62% specificity at a cutoff value of 1.525 (AUROC = 0.970) in diagnosing KCS. Scansys provides accurate KCP parameters in diagnosing KC; however, the efficiency of diagnosing KCS should be further optimized. [ABSTRACT FROM AUTHOR]

PurposeMethodsResultsConclusionThis study aimed to evaluate the tomographic, biomechanical, and in vivo confocal microscopic (IVCM) effects of chronic gout disease on human cornea.This prospective study included 60 eyes of 30 participants with chronic gout disease and 60 eyes of 30 healthy controls. Corneal thickness, keratometry (K) readings, and corneal aberrations were measured with Sirius 3 D corneal tomography system (Sirius, CSO, Italy). Corneal biomechanical properties (corneal hysteresis [CH], corneal resistance factor [CRF], and intraocular pressure [IOP] parameters) were assessed with an ocular response analyzer (ORA, Reichert Ophthalmic Instruments). The number and morphology of corneal endothelial cells and the number of basal epithelial cells were evaluated with IVCM (Confoscan 4.0). Tear breakup time (TBUT) was also evaluated.The mean diagnosis time of the patients with gout was 91.2 ± 69.6 months (12–300 month). Among corneal tomography measurements, K readings were similar between the two groups, while total and higher-order aberrations(coma, trefoil,s pherical, and quadrafoil) were significantly higher in the gout group. In the evaluation of biomechanical measurements, the CH value was significantly lower and the corneal-compensated IOP value was significantly higher in the gout group (p = 0.02, p = 0.01, respectively). The two groups did not significantly differ regarding the CRF or Goldmann IOP (p = 0.61, p = 0.15, respectively). Among the IVCM parameters, the number of corneal basal epithelial cells and the percentage of corneal endothelial hexagonality were significantly lower in the gout group, but no significant difference was detected in terms of the number of endothelial cells or polymegathism (p = 0.02, p < 0.001, p = 0.18, p = 0.59, respectively). While TBUT was significantly lower in the gout group (p < 0.001).This study showed that chronic gout disease increases the corneal aberrations and decreases the basal epithelial cell count, hexagonality ratio of endothelial cell and corneal biomechanics. [ABSTRACT FROM AUTHOR]

The study aimed to evaluate the precision of different Pentacam indices in diagnosing keratoconus (KC) in pediatric patients with and without Down Syndrome (DS) and determine suitable cutoff values. This prospective multicenter cross-sectional study evaluated 216 eyes of 131 patients aged 6–18 years (mean age 12.5 ± 3.2 years) using Pentacam. Patients were categorized into four groups: KC, forme fruste keratoconus (FK), DS, and control, excluding DS patients with topographic KC. Receiver operating characteristic curves were generated to determine the optimal cutoff points and compare the accuracy in identifying KC and FK in patients with and without DS. In DS patients, corneal morphology resembled KC features. The most effective indices for distinguishing KC in DS patients were the average pachymetric progression index (AUC = 0.961), higher-order aberration of the anterior cornea (AUC = 0.953), anterior elevation (AUC = 0.946), posterior elevation (AUC = 0.947), index of vertical asymmetry (AUC = 0.943), and Belin/Ambrosio enhanced ectasia total derivation value (AUC = 0.941). None of the indices showed good accuracy for distinguishing FK in DS patients. The thresholds of these indices differed significantly from non-DS patients. The results highlighted the need for DS-specific cutoff values to avoid false-positive or false-negative diagnoses in this population. [ABSTRACT FROM AUTHOR]

Abstract Keratoconus (KC) is an irreversible blinding eye disease; therefore, early screening of KC suspects (KCS) is crucial for protecting patients’ quality of life. Scheimpflug imaging is a commonly used screening device in clinical practice. We aimed to evaluate the diagnostic ability of a Scheimpflug imaging device (Scansys) for KC and KCS and compared it with other Scheimpflug-based devices (Pentacam and Corvis ST). This prospective case-control study included 107 normal eyes, 72 KCS, and 57 KC. Scansys screening index Keratoconus probability (KCP) showed excellent performance in diagnosing KC at a cutoff value of 16.4 (area under the receiver operating characteristic [AUROC] = 1.000), with 100% sensitivity and 98.11% specificity. KCP had a better KCS diagnostic ability at a cutoff value of 8.9 (AUROC = 0.813) than Corvis biomechanical index (CBI, AUROC = 0.764), reaching 67.61% sensitivity and 85.85% specificity. Pentacam screening index Belin/Ambrósio enhanced ectasia display deviation (BAD-D) showed the best performance with 92.96% sensitivity and 89.62% specificity at a cutoff value of 1.525 (AUROC = 0.970) in diagnosing KCS. Scansys provides accurate KCP parameters in diagnosing KC; however, the efficiency of diagnosing KCS should be further optimized.

Ana Marta,1,2 André Ferreira,1,3,4 Inês Couto,1 Miguel Mesquita Neves,1 Miguel Gomes,1 Luis Oliveira,1 Celia Azevedo Soares,5– 8 Maria João Menéres,1,2 Carolina Lemos,2,8 João Melo Beirão1,2 1Department of Ophthalmology, Centro Hospitalar Universitário de Santo António, Unidade Local de Saúde de Santo António, Porto, Portugal; 2Instituto Ciências Biomédicas Abel Salazar (ICBAS), Porto, Portugal; 3Department of Biomedicine - Unit of Anatomy, Faculty of Medicine of University of Porto, Porto, Portugal; 4Centre for Health Technology and Services Research, Health Research Network (CINTESIS@RISE), Faculty of Medicine of the University of Porto, Porto, Portugal; 5Medical Genetics Department, Centro Hospitalar Universitário de Santo António, Unidade Local de Saúde de Santo António, Porto, Portugal; 6Unit for Multidisciplinary Research in Biomedicine, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal; 7Medical Science Department, Universidade de Aveiro, Aveiro, Portugal; 8i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, PortugalCorrespondence: Ana Marta, Centro Hospitalar Universitário de Santo António, Unidade Saúde Local de Santo António, EPE (ULSSA), Largo do Prof. Abel Salazar, Porto, 4099-001, Portugal, Email analuisamarta2@gmail.comPurpose: Inherited retinal diseases (IRDs) are a group of degenerative disorders of the retina, that can be potentially associated with changes in the anterior segment, but their prevalence and impact are not known. Exploring these concomitant ophthalmologic changes with biomechanical assessment may help identify other non-retina causes of vision loss in these patients, such as corneal ectasia or susceptibility to glaucoma. This study aimed to measure and compare corneal biomechanics in patients with and without IRDs.Methods: A total of 77 patients (154 eyes) with IRD were recruited as the study group. The control group consisted of 77 healthy adults (154 eyes) with matched age and sphere equivalents. All participants underwent a comprehensive assessment including corneal tomography (Pentacam®) and biomechanical assessment (Corvis ST®). A total of 4 second-generation biomechanical parameters and 3 indexes were collected: Ambrosio Relational Thickness (ARTh), Deflection Amplitude Ratio Max (DARM), Integrated Radius (IR) and Stiffness Parameter at Applanation (SP-A1), the final deviation value D of the Belin/Ambrosio Enhanced Ectasia Display (BAD-D), Corvis Biomechanical Index (CBI) and Tomographic Biomechanical Index (TBI).Results: For IRD patients, there was a higher DARM (p < 0.001), lower ARTh (p < 0.001), higher CBI (p < 0.001), higher TBI (p< 0.001), and higher BAD-D (p < 0.001) compared to the control group. Regarding discrimination of healthy subjects and IRD patients, ARTh was the most sensitive parameter.Conclusion: The results showed that IRD patients tend to have softer corneal behaviour, compared to eyes without pathology, which may predispose patients to corneal ectasia or glaucoma development. ARTh could be used to screen IRD patients if a non-retina cause of vision loss is suspected.Keywords: IRD, corneal biomechanics, corneal tomography

Abstract Background This study proposes a decision support system created in collaboration with machine learning experts and ophthalmologists for detecting keratoconus (KC) severity. The system employs an ensemble machine model and minimal corneal measurements. Methods A clinical dataset is initially obtained from Pentacam corneal tomography imaging devices, which undergoes pre-processing and addresses imbalanced sampling through the application of an oversampling technique for minority classes. Subsequently, a combination of statistical methods, visual analysis, and expert input is employed to identify Pentacam indices most correlated with severity class labels. These selected features are then utilized to develop and validate three distinct machine learning models. The model exhibiting the most effective classification performance is integrated into a real-world web-based application and deployed on a web application server. This deployment facilitates evaluation of the proposed system, incorporating new data and considering relevant human factors related to the user experience. Results The performance of the developed system is experimentally evaluated, and the results revealed an overall accuracy of 98.62%, precision of 98.70%, recall of 98.62%, F1-score of 98.66%, and F2-score of 98.64%. The application's deployment also demonstrated precise and smooth end-to-end functionality. Conclusion The developed decision support system establishes a robust basis for subsequent assessment by ophthalmologists before potential deployment as a screening tool for keratoconus severity detection in a clinical setting.

Abstract Purpose: To investigate the effect of the near visual task of movie-watching in the straight gaze position on corneal topographic parameters. Methods: Thirty myopic young adults with an average age of 25.10 ± 4.13 years were recruited for the study. The designed near visual task consisted of watching a movie in the straight gaze position at a distance of 40 cm for 30 minutes. Corneal topography was performed using Oculus Keratograph 4 (OCULUS, Wetzlar, Germany) before and immediately after watching the movie, as well as at 10, 20, and 30 minutes intervals after completing this near visual task. Zernike coefficients, asphericity indices, refractive parameters, and diagnostic indices of keratoconus were recorded for statistical analysis. Results: Movie-watching at a close distance solely using the straight gaze position had no effect on Zernike coefficients (P > 0.130). Also, watching the movie had no effect on other corneal topography parameters including irregularities (P = 0.208), spherical eccentricity (P = 0.270), maximum decentration (P = 0.553), axis of maximum decentration (P = 0.186), peripheral astigmatism (P = 0.179), and average asphericity of the quadrants at 10 to 30º (P > 0.163). Conclusion: The results of the present study showed that watching movies in the straight gaze position had no effect on corneal topographic parameters and did not cause errors in corneal topographic measurements.

Background: To evaluate the corneal biomechanics of stable keratoconus suspects (Stable-KCS) at 1-year follow-up and compare them with those of subclinical keratoconus (SKC). Methods: This prospective case-control study included the eyes of 144 patients. Biomechanical and tomographic parameters were recorded (Corvis ST and Pentacam). Patients without clinical signs of keratoconus in both eyes but suspicious tomography findings were included in the Stable-KCS group (n = 72). Longitudinal follow-up was used to evaluate Stable-KCS changes. Unilateral keratoconus contralateral eyes with suspicious tomography were included in the SKC group (n = 72). T-tests and non-parametric tests were used for comparison. Multivariate general linear models were used to adjust for confounding factors for further analysis. Receiver operating characteristic (ROC) curves were used to analyze the distinguishability. Results: The biomechanical and tomographic parameters of Stable-KCS showed no progression during the follow-up time (13.19 ± 2.41 months, p > 0.05). Fifteen biomechanical parameters and the Stress–Strain Index (SSI) differed between the two groups (p < 0.016). The A1 dArc length showed the strongest distinguishing ability (area under the ROC = 0.888) between Stable-KCS and SKC, with 90.28% sensitivity and 77.78% specificity at the cut-off value of −0.0175. Conclusions: The A1 dArc length could distinguish between Stable-KCS and SKC, indicating the need to focus on changes in the A1 dArc length for keratoconus suspects during the follow-up period. Although both have abnormalities on tomography, the corneal biomechanics and SSI of Stable-KCS were stronger than those of SKC, which may explain the lack of progression of Stable-KCS. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the effect of the near visual task of movie-watching in the straight gaze position on corneal topographic parameters. Methods: Thirty myopic young adults with an average age of 25.10 ± 4.13 years were recruited for the study. The designed near visual task consisted of watching a movie in the straight gaze position at a distance of 40 cm for 30 minutes. Corneal topography was performed using Oculus Keratograph 4 (OCULUS, Wetzlar, Germany) before and immediately after watching the movie, as well as at 10, 20, and 30 minutes intervals after completing this near visual task. Zernike coefficients, asphericity indices, refractive parameters, and diagnostic indices of keratoconus were recorded for statistical analysis. Results: Movie-watching at a close distance solely using the straight gaze position had no effect on Zernike coefficients (P > 0.130). Also, watching the movie had no effect on other corneal topography parameters including irregularities (P = 0.208), spherical eccentricity (P = 0.270), maximum decentration (P = 0.553), axis of maximum decentration (P = 0.186), peripheral astigmatism (P = 0.179), and average asphericity of the quadrants at 10 to 30º (P >0.163). Conclusion: The results of the present study showed that watching movies in the straight gaze position had no effect on corneal topographic parameters and did not cause errors in corneal topographic measurements. [ABSTRACT FROM AUTHOR]

Fuchs endothelial corneal dystrophy (FECD) is a complex genetic disorder characterized by the slow and progressive degeneration of corneal endothelial cells. Thus, it may result in corneal endothelial decompensation and irreversible corneal edema. Moreover, FECD is associated with alterations in all corneal layers, such as thickening of the Descemet membrane, stromal scarring, subepithelial fibrosis, and the formation of epithelial bullae. Hence, anterior segment imaging devices that enable precise measurement of functional and anatomical changes in the cornea are essential for the management of FECD. In this review, the authors will introduce studies on the application of various imaging modalities, such as anterior segment optical coherence tomography, Scheimpflug corneal tomography, specular microscopy, in vitro confocal microscopy, and retroillumination photography, in the diagnosis and monitoring of FECD and discuss the results of these studies. The application of novel technologies, including image processing technology and artificial intelligence, that are expected to further enhance the accuracy, precision, and speed of the imaging technologies will also be discussed. [ABSTRACT FROM AUTHOR]

PurposeEctasia screening in candidates for laser refractive surgery is mandatory during preoperative evaluation. Despite the availability of modern imaging techniques, refractive surgeons often face borderline decisions when patients present with suspicious tomographic findings. This case series presents refractive candidates with suspicious tomographic findings and demonstrates how to interpret them using Scheimpflug imaging and additional anterior segment optical coherence tomography (AS-OCT).SettingDepartment of Ophthalmology, University Hospital, LMU Munich.Case seriesThis case series examines six potential candidates for refractive surgery with a mean age of 29.2 ± 3.9 years, whose corneal assessments using Scheimpflug imaging raised suspicion for ectasia. Each candidate was additionally examined with AS-OCT and reevaluated. The mean manifest subjective spherical equivalent was -3.67 ± 1.8 diopters. The total corneal thickness measured 537 µm ± 30 µm at its thinnest point. None of the candidates had any reported underlying corneal or ophthalmic diseases, and slit lamp examinations revealed no abnormal morphological findings.ConclusionsBoth Scheimpflug imaging and AS-OCT are appropriate tools for screening refractive candidates for ectasia. While topographic and elevation analyses yielded comparable results regarding corneal structure, the epithelial mapping provided by AS-OCT played a critical role in decision-making for cases with borderline tomographic findings. Establishing a global consensus on the use of epithelial mapping in ectasia screening is necessary.

PURPOSE: The purpose of this study is to investigate visual and tomographic outcomes and complications of long-arc length intrastromal corneal ring segment (ICRS) implantation for the treatment of advanced keratoconus. MATERIALS AND METHODS: This retrospective study enrolled 10 eyes of 9 subjects. All patients received 320-degree ICRS (320-ICRS) implantation with femtosecond laser-assisted technique based on their advanced grading with preoperative high keratometry (K) value, asphericity (Q), and astigmatism. Medical records and corneal tomography changes of consecutive patients were reviewed at baseline, 1, and 3 months after treatment. RESULTS: There are 6 female and 3 male patients with a mean age of 29.6 ± 7.8 years in this study. Mean K (Km) reduced from 59.01 ± 5.81 D preoperatively to 50.7 ± 5.3 and 50.2 ± 3.66 postoperatively (after 1 month and 3 months respectively, P < 0.001). The changes in mean K, K1, K2, and maximum K (Kmax) reading were all statistically significant (all P < 0.001). Mean uncorrected distance visual acuity (UCVA) improved from 20/400 to 20/200. Mean best-corrected distance visual acuity (BCVA) improved from 20/100 to 20/60. Both UCVA and BCVA showed a trend of improvement at postoperative month 3, though insignificant in BCVA (P = 0.114). Mean Q improved from −1.59 ± 0.62 preoperatively to −0.48 ± 1.08 and −0.11 ± 1.04 postoperatively (after 1 month and 3 months respectively, P = 0.016, 0.002). No intraoperative or postoperative complications were observed. CONCLUSIONS: The present results suggest that implanting a 320-ICRS is a safe and effective procedure for treating patients with advanced keratoconus. Preoperative corneal measurements and the selection of types and thickness of ICRS are important to prevent unpredictable results.

Pedro Carreira, Tomás Loureiro, Ana Rita Carreira, Filipe Gouveia-Moraes, Ana Cardoso, Audrey Sampaio, Paul Campos, Sandra Rodrigues-Barros, Ines Machado, Nuno Campos Centro de Responsabilidade Integrada de Oftalmologia, Hospital Garcia de Orta, Almada, PortugalCorrespondence: Tomás Loureiro, Centro de Responsabilidade Integrada de Oftalmologia, Hospital Garcia de Orta, E.P.E, Av. Torrado da Silva, Almada, 2805-267, Portugal, Email loureiro.tomas@gmail.comIntroduction: Upper tarsal mechanical forces influence corneal epithelial thickness profile, which could modulate corneal astigmatism. Upper eyelid blepharoplasty reduces upper tarsal strength and may have an impact on ocular surface. The aim of this study is to evaluate the effect of upper eyelid blepharoplasty on corneal epithelial thickness profile, astigmatism and aberrations.Methods: Patients with dermatochalasis underwent bilateral upper eyelid blepharoplasty. Anterior segment optical coherence tomography (AS-OCT) (Zeiss Cirrus 5000 HD-OCT) and Pentacam (Oculus, Wetzlar Germany) were performed before surgery and in the 8th postoperative week. Corneal epithelial thickness, keratometry, aberrations and asphericity were considered for statistical purposes. Only right eyes were considered. A p-value lower than 0.05 was considered significant.Results: Thirty eyes of 30 patients were included. The degree of astigmatism did not change after surgery (0.95D vs 0.83D, p=0.23). The difference between preoperative and postoperative steepest axis was 3.1° (p=0.04) with a tendency to change toward the vertical meridian. Mean epithelial thickness was higher in the inferior region both pre- and postoperatively and did not change. ET in the superior octant was lower (42 μm vs 45 μm, p< 0.01) and the difference between inferior and superior octants (I-S) was higher (7 μm vs 3 μm, p< 0.001) before surgery. There were no statistically significant changes in corneal aberrations (p=0.52) and asphericity (p=0.41) after surgery.Conclusion: Our results support that upper tarsus pressure influences epithelial thickness profile and, consequently, the corneal steepest keratometry. These results lead us to postulate that upper eyelid blepharoplasty may influence biometric and keratometric measurements.Keywords: Blepharoplasty, Epithelial Thickness, Corneal Tomography, Anterior-Segment Optical Coherence Tomography

Abstract Different diagnostic approaches for ectatic corneal diseases (ECD) include screening, diagnosis confirmation, classification of the ECD type, severity staging, prognostic evaluation, and clinical follow-up. The comprehensive assessment must start with a directed clinical history. However, multimodal imaging tools, including Placido-disk topography, Scheimpflug three-dimensional (3D) tomography, corneal biomechanical evaluations, and layered (or segmental) tomography with epithelial thickness by optical coherence tomography (OCT), or digital very high-frequency ultrasound (dVHF-US) serve as fundamental complementary exams for measuring different characteristics of the cornea. Also, ocular wavefront analysis, axial length measurements, corneal specular or confocal microscopy, and genetic or molecular biology tests are relevant for clinical decisions. Artificial intelligence enhances interpretation and enables combining such a plethora of data, boosting accuracy and facilitating clinical decisions. The applications of diagnostic information for individualized treatments became relevant concerning the therapeutic refractive procedures that emerged as alternatives to keratoplasty. The first paradigm shift concerns the surgical management of patients with ECD with different techniques, such as crosslinking and intrastromal corneal ring segments. A second paradigm shift involved the quest for identifying patients at higher risk of progressive iatrogenic ectasia after elective refractive corrections on the cornea. Beyond augmenting the sensitivity to detect very mild (subclinical or fruste) forms of ECD, ectasia risk assessment evolved to characterize the inherent susceptibility for ectasia development and progression. Furthermore, ectasia risk is also related to environmental factors, including eye rubbing and the relational impact of the surgical procedure on the cornea.

The study aimed to evaluate the precision of different Pentacam indices in diagnosing keratoconus (KC) in pediatric patients with and without Down Syndrome (DS) and determine suitable cutoff values. This prospective multicenter cross-sectional study evaluated 216 eyes of 131 patients aged 6–18 years (mean age 12.5 ± 3.2 years) using Pentacam. Patients were categorized into four groups: KC, forme fruste keratoconus (FK), DS, and control, excluding DS patients with topographic KC. Receiver operating characteristic curves were generated to determine the optimal cutoff points and compare the accuracy in identifying KC and FK in patients with and without DS. In DS patients, corneal morphology resembled KC features. The most effective indices for distinguishing KC in DS patients were the average pachymetric progression index (AUC = 0.961), higher-order aberration of the anterior cornea (AUC = 0.953), anterior elevation (AUC = 0.946), posterior elevation (AUC = 0.947), index of vertical asymmetry (AUC = 0.943), and Belin/Ambrosio enhanced ectasia total derivation value (AUC = 0.941). None of the indices showed good accuracy for distinguishing FK in DS patients. The thresholds of these indices differed significantly from non-DS patients. The results highlighted the need for DS-specific cutoff values to avoid false-positive or false-negative diagnoses in this population.

Background: This study investigated the prevalence, risk factors and severity of corneal tomographic features of keratoconus in Down syndrome (DS). Additionally, previous studies indicate anomalous corneal features in DS, without keratoconus, this study characterised corneal features in DS without keratoconus. Methods: This prospective observational study included participants with DS ≥10 years old. Keratoconus diagnosis, risk factors and corneal tomographic characteristics were recorded. Participants underwent slit‐lamp biomicroscopy, Scheimpflug corneal tomography, corneal topography and autorefraction. A diagnosis of keratoconus (DS‐KC), suspect keratoconus (DS‐SK) and non‐keratoconus (DS‐NK) was made based on expert review of scans by three fellowship trained anterior segment ophthalmologists. Corneal tomography parameters from one eye of each participant were analysed. Results: Keratoconus affected 50 (26.3%) of 190 participants, diagnosed by corneal tomography, topography or slit‐lamp signs. Corneal hydrops affected 14.0% of DS‐KC participants. Eye rubbing was a significant risk factor for keratoconus (p = 0.036). 175 (92%) participants could undertake corneal tomography of which tomography assessment alone identified 47 (26.9%) DS‐KC participants, 64 (36.6%) DS‐SK participants and 64 (36.6%) DS‐NK participants. Significant differences (p < 0.001) were identified when the DS‐KC, DS‐SK and DS‐NK groups were compared in maximum keratometry and posterior elevation at the thinnest point respectively: median (interquartile range) 50.20 (10.30D), 47.60 (1.95D), 46.50 (2.40D); 24.0 (38.00 μm), 10.00 (13.75 μm), 8.00 (6.00 μm). The DS‐SK and DS‐NK cohorts had similar minimum pachymetry, however, had several significantly different parameters among which included greater maximum keratometry, posterior elevation at the thinnest point in the DS‐SK group. Conclusions: Keratoconus is common in DS. Keratoconus screening with corneal tomography is recommended for early detection. [ABSTRACT FROM AUTHOR]

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Purpose: To introduce the novel parameter of Corneal Contribution to Stress (CCS) and compare stress distribution patterns between keratoconus (KCN) and normal corneas. Design: Prospective, observational, cross-sectional study. Participants: The study included 66 eyes of 40 subjects diagnosed with KCN and 155 left eyes from 155 normal control (NRL) subjects. Methods: Tomography was obtained to calculate the newly proposed CCS, defined according to the hoop stress formula without intraocular pressure, R/2t, where R is the radius of curvature and t is the thickness. CCS maps were calculated from pachymetry and tangential curvature maps. Custom software identified the 2-mm-diameter zones of greatest curvature (Cspot-max), thinnest pachymetry (Pach-min), greatest stress (CCSmax), and lowest stress (CCSmin). Stress difference (CCSdiff) was calculated as CCSmax – CCSmin. Distances between Cspot-max vs. Pach-min, vs. CCSmax, and vs. CCSmin, as well as between Pach-min vs. CCSmax and vs. CCSmin, were calculated. t tests were performed between cohorts, and paired t tests were performed within cohorts. Univariate linear regression analyses were performed between parameters and distances. The significance threshold was P < 0.05. Main Outcome Measures: Corneal stress parameters, corneal features of maximum curvature, minimum thickness, and distances between corneal stress parameters and corneal features. Results: CCSmax was significantly closer to Pach-min (0.79 ± 0.92) and Cspot-max (2.04 ± 0.85) than CCSmin (3.17 ± 0.38, 2.73 ± 1.53, respectively) in NRL, P < 0.0001, whereas CCSmin was significantly closer to Cspot-max (1.35 ± 1.43) than CCSmax (2.52 ± 0.72) in KCN, P < 0.0001. Cspot-max (severity) was significantly related to CCSdiff in KCN (P < 0.0001; R2 = 0.5882) with a weak relationship in NRL (P < 0.0080, R2 = 0.0451). Cspot-max was significantly related to the distance from Pach-min to CCSmax (P < 0.0001; R2 = 0.3737) without significance in NRL (P = 0.8011). Conclusions: Corneal stress is driven by thickness in NRL, with greatest stress at thinnest pachymetry and greatest curvature. However, maximum stress moves away from thinnest pachymetry with progression in KCN, and minimum stress is associated with maximum curvature. Severity in KCN is significantly related to greater difference between maximum and minimum stress, consistent with the biomechanical cycle of decompensation. Financial Disclosure(s): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Abstract Background To compare the rate of fractional change for multiple corneal tomographic factors in progressive keratoconus (KC). Methods In this retrospective case series, 40 eyes (40 patients) with progressive KC (increase in central keratometry of 1.00 D or maximum keratometry of 1.50 D on two visits at least six months apart) were included. Cases with previous history of ocular surgery, poor scans, corneal scars, severe dry eyes, post-excimer ectasia, pellucid marginal degeneration were excluded. Medical records, corneal tomography and anterior corneal wavefront (8 mm) (Scheimpflug tomography, Pentacam, Oculus, Germany) were analyzed. Rate of fractional change (Rx = (x1 − x0)/(|x0|tm)); where, x1 = value at follow-up, x0 = value at initial visit and tm = time in months, was measured. Results The mean age of the patients was 30.0 ± 8.4 years. The mean follow-up duration was 8.9 ± 4.2 months. Coma (0.076 ± 1.4) had the largest rate of fractional change (P = 1.7 × 10−14, Kruskal–Wallis test). The rate of fractional change was higher for aberrometric parameters (anterior corneal higher-order aberrations root mean square and anterior coma) compared to pachymetric and keratometric parameters (P values ranging from 1.4 × 10−4 to 7.4 × 10−10, Mann–Whitney test, effect size ranging from 0.4–0.7). The rate of fractional change was comparable between pachymetric and keratometric factors (P > 0.05 for all comparisons, Mann–Whitney test). Conclusions Anterior corneal wavefront, especially anterior coma, were noted to have higher rate of fractional change compared to single point keratometric and pachymetric indices in progressive KC. This information can be used for decision-making when monitoring patients with KC.

Wyatt M Corbin,1 Carter J Payne,2,3 Hamed Momeni-Moghaddam,4 Yasmyne C Ronquillo,2 Phillip C Hoopes Snr,2 Majid Moshirfar2,5,6 1Stritch School of Medicine, Loyola University Chicago, Maywood, IL, USA; 2Hoopes Vision Research Center, Hoopes Vision, Draper, UT, USA; 3Case Western Reserve University School of Medicine, Cleveland, OH, USA; 4Rehabilitation Sciences Research Center, Zahedan University of Medical Sciences, Zahedan, Iran; 5Moran Eye Center, University of Utah, Salt Lake City, UT, USA; 6Utah Lion’s Eye Bank, Murray, UT, USACorrespondence: Majid Moshirfar, Hoopes Vision Research Center, Hoopes Vision, 11820 S. State St. Ste. 200, Draper, UT, 84020, USA, Tel +1 801 568-0200, Fax +1 801 563-0200, Email cornea2020@me.comAbstract: Increasing popularity and utility of epithelial thickness mapping (ETM) in keratorefractive surgery screening may begin to inappropriately devalue the use of tomography. An increasing body of research suggests that the interpretation of ETM based solely on the corneal resurfacing function may be insufficient to screen and select patients for refractive surgery. ETM and tomography are complementary and, when used together, may provide the safest and most optimal tools for keratorefractive surgery screening.Keywords: corneal tomography, corneal topography, corneal epithelial map, SMILE, LASIK, PRK

Purpose: Osteogenesis imperfecta (OI) is a rare inherited disease affecting collagen-rich tissues. Ocular complications have been reported such as thin corneas, low ocular rigidity, keratoconus, among others. The purpose of this study is to characterize corneal tomographic features in OI patients compared to unaffected patients, with particular focus on commonly studied keratoconus indices. Methods: Cross-sectional case–control study including 37 OI patients and 37 age-matched controls. Patients and controls underwent comprehensive ophthalmological examination including corneal Scheimpflug tomography with a Pentacam HR device (Oculus Optikgeräte GmbH, Wetzlar, Germany) to analyse and compare topometric, tomographic, pachymetric and Belin-Ambrósio Enhanced Ectasia Display III (BAD-D) data of both eyes of each patient. Results: Most OI patients had type I disease (n = 24; 65%) but type III–VII patients were also included. Two patients had clinically overt bilateral keratoconus. OI patients had significantly higher maximum keratometry (45.2 ± 2.1 vs. 43.7 ± 1.2; p = 0.0416), front and back elevation (3.0 ± 3.3 vs. 2.1 ± 1.3, p = 0.0201; 11.1 ± 8.2 vs. 5.0 ± 3.7, p < 0.0001), index of surface variance (25.5 ± 13 vs. 17.4 ± 8.3; p = 0.0016), index of vertical asymmetry (0.21 ± 0.14 vs. 0.15 ± 0.06; p = 0.0215), index of height asymmetry (9.2 ± 14 vs. 6.0 ± 4.5; p = 0.0421), index of height decentration (0.02 ± 0.01 vs. 0.01 ± 0.01; p < 0.0001) and average pachymetric progression (1.01 ± 0.19 vs. 0.88 ± 0.14; p < 0.0001) readings. Thinnest corneal thickness and maximum Ambrósio relational thickness were significantly lower (477 ± 52 vs. 543 ± 26; 387 ± 95 vs. 509 ± 49; p < 0.0001). Two-thirds of OI patients had corneas with a minimum thickness < 500 µm. BAD-D value was significantly higher in OI patients (2.1 ± 1.4 vs. 0.9 ± 0.2; p < 0.0001). Conclusion: OI patients showed significant changes in corneal profiles compared with healthy subjects. A high proportion of patients had tomographically suspect corneas when using keratoconus diagnostic indices. Further studies are warranted to assess the true risk of corneal ectasia in OI patients. [ABSTRACT FROM AUTHOR]

Background: To evaluate the corneal biomechanics of stable keratoconus suspects (Stable-KCS) at 1-year follow-up and compare them with those of subclinical keratoconus (SKC). Methods: This prospective case-control study included the eyes of 144 patients. Biomechanical and tomographic parameters were recorded (Corvis ST and Pentacam). Patients without clinical signs of keratoconus in both eyes but suspicious tomography findings were included in the Stable-KCS group (n = 72). Longitudinal follow-up was used to evaluate Stable-KCS changes. Unilateral keratoconus contralateral eyes with suspicious tomography were included in the SKC group (n = 72). T-tests and non-parametric tests were used for comparison. Multivariate general linear models were used to adjust for confounding factors for further analysis. Receiver operating characteristic (ROC) curves were used to analyze the distinguishability. Results: The biomechanical and tomographic parameters of Stable-KCS showed no progression during the follow-up time (13.19 ± 2.41 months, p > 0.05). Fifteen biomechanical parameters and the Stress–Strain Index (SSI) differed between the two groups (p < 0.016). The A1 dArc length showed the strongest distinguishing ability (area under the ROC = 0.888) between Stable-KCS and SKC, with 90.28% sensitivity and 77.78% specificity at the cut-off value of −0.0175. Conclusions: The A1 dArc length could distinguish between Stable-KCS and SKC, indicating the need to focus on changes in the A1 dArc length for keratoconus suspects during the follow-up period. Although both have abnormalities on tomography, the corneal biomechanics and SSI of Stable-KCS were stronger than those of SKC, which may explain the lack of progression of Stable-KCS.

Fuchs endothelial corneal dystrophy (FECD) is a complex genetic disorder characterized by the slow and progressive degeneration of corneal endothelial cells. Thus, it may result in corneal endothelial decompensation and irreversible corneal edema. Moreover, FECD is associated with alterations in all corneal layers, such as thickening of the Descemet membrane, stromal scarring, subepithelial fibrosis, and the formation of epithelial bullae. Hence, anterior segment imaging devices that enable precise measurement of functional and anatomical changes in the cornea are essential for the management of FECD. In this review, the authors will introduce studies on the application of various imaging modalities, such as anterior segment optical coherence tomography, Scheimpflug corneal tomography, specular microscopy, in vitro confocal microscopy, and retroillumination photography, in the diagnosis and monitoring of FECD and discuss the results of these studies. The application of novel technologies, including image processing technology and artificial intelligence, that are expected to further enhance the accuracy, precision, and speed of the imaging technologies will also be discussed.

Purpose: To analyze and compare sensitive in vivo characteristics for screening early keratoconus.Methods: This multicenter, case-control study included 712 eyes, after matching for age and biomechanically corrected intraocular pressure, from three clinics in different cities. The keratoconus (n = 288), early keratoconus (n = 91), and normal cornea (n = 333) groups included eyes diagnosed with bilateral keratoconus, fellow eyes with relatively normal topography with unilateral keratoconus, and normal eyes before refractive surgery, respectively. After adjusting for central corneal thickness, differences in vivo characteristics were analyzed among the three groups. The in vivo characteristics were measured by Pentacam and Corvis ST. Fifty-four indices were evaluated to screen for a sensitive index for the detection of early keratoconus.Results: Significant differences were observed in 26 of the 36 corneal biomechanical indeces between the early keratoconus and normal corneas. The area under the receiver operating characteristic curve of tomographic and biomechanical index, Belin/Ambrósio deviation, and Da in differentiating keratoconus from normal cornea was 1.000. Among the top five indeces of the area under the receiver operating characteristic curve for detecting early keratoconus, the corneal biomechanical-related index accounted for 80% (4/5), including A1 dArc length, highest concavity radius, A2 time, and tomographic and biomechanical index, of which the area under the receiver operating characteristic curve of A1 dArc length was 0.901.Conclusion: A1 dArc length and several corneal biomechanical indices are highly sensitive for the detection of early keratoconus, even in the absence of topographic abnormalities. Ophthalmologists should focus on the clinical application of corneal biomechanics and combine corneal tomography for the timely and accurate detection of early keratoconus.

Purpose: The purpose of the study is to investigate the effects of combined 0.8% tropicamide and 5% phenylephrine on the corneal parameters using Pentacam. Methods: The study was performed on 200 eyes of 100 adult patients visiting the ophthalmology clinic for evaluation of refractive errors or cataract screening. Mydriatic drops (Tropifirin; Java, India) containing tropicamide 0.8%, phenylephrine hydrochloride 5%, and chlorbutol 0.5% (as a preservative) were instilled into the eyes of the patients three times every 10 minutes. The Pentacam was repeated after 30 minutes. The measurement data of various corneal parameters from different Pentacam displays (keratometry, pachymetry, densitometry, and Zernike analysis) was manually compiled on an Excel spreadsheet and analyzed using Statistical Package for the Social Sciences (SPSS) 20 software. Results: Analysis of Pentacam refractive maps revealed a statistically significant increase (P < 0.05) in the values of radius peripheral (cornea front), pupil center Pachymetry, pachymetry apex, thinnest location Pachymetry, and cornea volume. However, pupil dilation did not affect the Q-value (asphericity). Analysis of the densitometry values revealed significant increase in all zones. Aberrations maps revealed statistically significant increase in the value of spherical aberration after the induction of mydriasis, but the values of Trefoil 0º, Trefoil 30º, Koma 90º, and Koma 0º were not affected significantly. We did not observe any untoward effect of the drug, except transient blurring of vision. Conclusion: The current study showed that routine mydriasis in the eye clinics leads to a significant increase in various corneal parameters including corneal pachymetry, cornea densitometry, and spherical aberration as measured by Pentacam, which can influence the decision-making in the management of various corneal diseases. The ophthalmologists should be aware of these issues and make adjustments in their surgical planning accordingly.

Omar Alshehri,1 Ahmed M Abdelaal,2 Ghufran Abudawood,1 Muhammad A Khan,3 Saud Alsharif,4 Hassan Hijazi,1 AlBaraa AlQassimi1 1Ophthalmology Department, King Fahad Armed Forces Hospital, Jeddah, Saudi Arabia; 2Ophthalmology Department, Prince Sultan Military Medical City, Riyadh, Saudi Arabia; 3Epidemiology and Public Health Department, King Saud Bin Abdulaziz University, Jeddah, Saudi Arabia; 4Faculty of Medicine, Imam Mohammad Ibn Saud Islamic University, Riyadh, Saudi ArabiaCorrespondence: Ahmed M Abdelaal, Ophthalmology Department, Prince Sultan Military Medical City, Riyadh, Saudi Arabia, Tel +966 56 371 8789, Email ahmed3bdelaal@gmail.comPurpose: Anterior segment evaluation using Scheimpflug imaging with the Pentacam scanner allows the acquisition of a plethora of information. It aids in screening and diagnosing corneal pathologies and determining suitability for keratorefractive procedures. This research has significant benefits in terms of establishing normative tomographic values, which is crucial in countries where Keratoconus (KC) is more prevalent, especially among young age group, along with aiding future research in the field of refractive surgery by providing relevant normative data.Methods: A retrospective review of digital corneal tomography images for a group of medically and ophthalmologically free males aged between 18 and 21 years with 20/20 unaided distant visual acuity was performed.Results: A total of 1272 subjects (2544 eyes) were included. Findings revealed a mean maximal corneal curvature (Kmax) of 42.91 ± 1.40D (range 36.90– 47.80D). The mean flat keratometry (K1) was 41.87 ± 1.31D (range 36.00– 46.40D). The mean steep keratometry (K2) was 42.66 ± 1.35D (range 36.70– 47.60D). The mean corneal astigmatism (CA) was 0.79 ± 0.37D (range 0.00D-2.30D). The mean central corneal thickness (CCT) was 558.53 ± 33.84 μm (range 421– 677 μm). The mean thinnest corneal location thickness (TCLT) was 551.64 ± 34.08 μm (range 417– 669μm). The mean corneal diameter (CD) and anterior chamber depth (ACD) were 12.13 ± 0.39 mm (range 10.50– 13.60 mm) and 3.12 ± 0.29 mm (range 2.08– 4.08 mm), respectively. The median differences between both eyes of the same subject were as follows: kmax difference of 0.20D (IQR 0.1– 0.4); K1, K2 and CA difference of 0.20D (IQR 0.1– 0.3) for all 3 parameters; CCT and TCLT difference of 5.00 μm (IQR 3.0– 9.0) and 6.00 μm (IQR 3.0– 10.0), respectively; CD difference of 0.10 mm (IQR 0.0– 0.1); and ACD difference of 0.04 (IQR 0.02– 0.06).Conclusion: We believe our data can aid in establishing normative tomographic values and acceptable differences between both eyes. Our data may also help detect subtle corneal pathology and be useful for researchers and innovators in the field of ophthalmology.Keywords: corneal tomography, corneal topography, pentacam, normative values, Saudi Arabia

Purpose: To evaluate the accuracy of different corneal parameters in detecting keratoconus using a dual Scheimpflug/Placido system (Sirius, CSO, Italy). Methods: Sixty-eight eyes of 68 keratoconus patients and 77 eyes of 77 normal subjects were prospectively assessed in a diagnostic test study. The mean differences of the corneal parameters were compared using the independent t-test. The accuracy of curvature, elevation, pachymetry, and aberrometry indices, aqueous depth, and corneal volume in 10 mm was evaluated using the area under the curve (AUC), and the DeLong method was used for the comparison of AUCs. Multiple tests in a parallel manner and multiple logistic regression analysis were applied to determine the best predictor indices. Results: All indices except aqueous depth and corneal volume were significantly different between the two groups (P < 0.001). Back keratoconus vertex (KVb) and front Baiocchi–Calossi–Versaci index (BCVf) had the highest sensitivity (for both 98.53%) followed by front symmetry index (SIf) (96.12%) and thinnest point of the cornea (88.24%) in elevation, aberrometry, curvature, and pachymetry parameters, respectively. The highest diagnostic ability was observed in KVb (AUC 0.993) and BCVf index (AUC 0.992) (DeLong > 0.05). Multiple test analysis showed a combination of indices with the highest accuracy that was similar to the performance of each one individually, and keratoconus was diagnosed correctly in 98.5% of the cases (R2 = 93%). Conclusion: The parameters extracted from Sirius can differentiate keratoconus from normal corneas with high accuracy without the need for complex computational algorithms. Elevation-based and combined aberrometry indices had the highest diagnostic power. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of the study is to investigate the effects of combined 0.8% tropicamide and 5% phenylephrine on the corneal parameters using Pentacam. Methods: The study was performed on 200 eyes of 100 adult patients visiting the ophthalmology clinic for evaluation of refractive errors or cataract screening. Mydriatic drops (Tropifirin; Java, India) containing tropicamide 0.8%, phenylephrine hydrochloride 5%, and chlorbutol 0.5% (as a preservative) were instilled into the eyes of the patients three times every 10 minutes. The Pentacam was repeated after 30 minutes. The measurement data of various corneal parameters from different Pentacam displays (keratometry, pachymetry, densitometry, and Zernike analysis) was manually compiled on an Excel spreadsheet and analyzed using Statistical Package for the Social Sciences (SPSS) 20 software. Results: Analysis of Pentacam refractive maps revealed a statistically significant increase (P < 0.05) in the values of radius peripheral (cornea front), pupil center Pachymetry, pachymetry apex, thinnest location Pachymetry, and cornea volume. However, pupil dilation did not affect the Q-value (asphericity). Analysis of the densitometry values revealed significant increase in all zones. Aberrations maps revealed statistically significant increase in the value of spherical aberration after the induction of mydriasis, but the values of Trefoil 0º, Trefoil 30º, Koma 90º, and Koma 0º were not affected significantly. We did not observe any untoward effect of the drug, except transient blurring of vision. Conclusion: The current study showed that routine mydriasis in the eye clinics leads to a significant increase in various corneal parameters including corneal pachymetry, cornea densitometry, and spherical aberration as measured by Pentacam, which can influence the decision-making in the management of various corneal diseases. The ophthalmologists should be aware of these issues and make adjustments in their surgical planning accordingly. [ABSTRACT FROM AUTHOR]

Abstract Background Keratoconus (KC) is a noninflammatory corneal ectatic disorder. In 2015, the Global Consensus on Keratoconus and Ectatic Diseases agreed that the pathophysiology of KC includes environmental, biomechanical, genetic, and biochemical disorders on one hand, and that true unilateral KC does not exist on the other hand. However, with the increasingly advancements in detection methods, we report the first case of a stable unilateral keratoconus with the longest follow up period of 14 years (2006–2020). We used topographic, tomographic, and biomechanical values for both eyes over the years to confirm the diagnosis, which has never been done before. Our study focuses on a single patient therefore it illustrates the mere possibility that unilateral keratoconus exists. Case presentation We present the case of a 19-year-old male with no previous ocular or general health conditions who presented to our clinic in November 2006 for incidental finding of decreased vision of the right eye (OD) on a routine examination. Topographies, tomographies, and biomechanical analysis of both eyes were obtained and showed a unilateral right keratoconus at the time. Patient admitted to unilateral right eye rubbing. Although we cannot prove that previous eye rubbing alone led to these initial symptoms, he was advised to stop rubbing and was followed up without any intervention for fourteen years during which topographic, tomographic, and biomechanical values for both eyes remained stable, proving for the first time that unilateral KC could exist. Conclusion We think that the data we are presenting is important because acknowledging that true unilateral keratoconus exists questions the genetic or primary biomechanical etiology of keratoconus versus the secondary biomechanical etiologies like eye rubbing. Our report also shows the importance of corneal biomechanics in detecting early changes. This is important to detect early, prevent progression, and tailor treatment.

Tomoya Nishida,1 Takashi Kojima,1,2 Takahiro Kataoka,1 Naoki Isogai,1 Yoko Yoshida,1 Tomoaki Nakamura1 1Nagoya Eye Clinic, Nagoya, Japan; 2Department of Ophthalmology, Keio University School of Medicine, Tokyo, JapanCorrespondence: Takashi Kojima, Department of Ophthalmology, Keio University School of Medicine, Shinanomachi 35, Shinjuku-ku, Tokyo, Japan, Tel +81-3-5363-2012, Fax +81-3-3359-7027, Email kojkoj@me.comPurpose: This study aimed to investigate the relationship between changes in corneal biomechanical properties and changes in anterior segment optical coherence tomography (AS-OCT) parameters preoperatively and following customized corneal cross-linking (C-CXL) in eyes with progressive keratoconus.Patients and Methods: This study included 44 eyes of 44 patients (33 men, 11 women; average age 22.8 ± 6.4 years) who underwent C-CXL for progressive keratoconus. Scheimpflug-based tonometer (SBT) and AS-OCT findings were evaluated preoperatively and 3 months following CXL. Parameters related to changes in SBT parameters were examined by multiple regression analysis using the stepwise method.Results: Regarding SBT parameters, significant changes were observed in the integrated area under the curve of the inverse concave radius (pre, 12.19 ± 1.95/mm; post, 11.26 ± 1.89/mm; p < 0.0001), maximum inverse radius (pre, 0.24 ± 0.04/mm; post, 0.23 ± 0.04/mm; p = 0.0053), deformation amplitude ratio max 2 mm (pre, 5.53 ± 0.81; post, 5.29 ± 0.71; p = 0.0048), and stress–strain index (pre, 0.74 ± 0.16; post, 0.84 ± 0.20; p < 0.0001), pre and post C-CXL. Regarding AS-OCT parameters, significant changes were observed in average keratometry (pre, 47.87 ± 3.61 D; post, 47.56 ± 3.29 D, p = 0.0104), steep keratometry (pre, 49.61 ± 4.01 D; post, 49.25 ± 3.59 D; p = 0.0115), maximum keratometry (pre, 55.44 ± 6.22 D; post, 54.68 ± 5.56 D; p = 0.0061), and thinnest corneal thickness (pre, 450.43 ± 41.74 μm; post, 444.00 ± 39.35 μm; p < 0.0001), pre and post C-CXL. Multiple regression analysis demonstrated that when the change in the deformation amplitude (DA) ratio max (2 mm) was the dependent variable, age, change in average keratometry, and change in the thinnest corneal thickness were selected as explanatory variables. When changes in the stiffness parameter at applanation 1 and stress–strain index were the dependent variables, change in the intraocular pressure (IOP) was selected as the explanatory variable.Conclusion: Change in the SBT parameters following C-CXL could be related to the age, change in the IOP value, change in average keratometry, and thinnest corneal thickness.Keywords: keratoconus, corneal biomechanics, corneal tomography, customized corneal cross-linking

Background: Corneal power measurement is essential for IOL power calculation. Conventional keratometry measures the anterior corneal surface using a standard keratometric index without measuring the posterior corneal surface. Schiempflug imaging have added the ability to measure posterior corneal surface which may affect IOL power calculation and postoperative refraction. Purpose: To evaluate different keratometric measurements including Simulated keratometry (SimK), true net power (TNP), total corneal refractive power (TCRP) and equivalent K reading (EKR) obtained from corneal tomography in IOL power calculation and compare the predicted refraction of calculated IOL power with postoperative subjective refraction. Materials and Methods: Sixty-five cataractous eyes were included in this prospective interventional case series. Four corneal power measurements using Pentacam AXL were analyzed: SimK over 3mm, TNP over 4mm, TCRP over 3mm and EKR over 4.5mm. The IOL power was calculated using Barrett Universal II formula. Results: No statistically significant difference between SimK and EKR (p- value=1.000) while TNP and TCRP were statistically significantly higher than SimK (p-value<0.001) with mean difference 1.2+/-0.2D and 0.67+/-0.34D respectively. The mean prediction error of refractive outcome was -0.006+/-0.32D for SimK, -0.02+/- 0.5D for EKR, 1.08+/-0.4D for TNP and 0.56+/-0.46D for TCRP. Conclusion: Corneal power measurements using SimK and EKR displayed comparable accuracy in IOL power calculation and postoperative refraction while TNP and TCRP were far away. [ABSTRACT FROM AUTHOR]

The study aims to investigate the likelihood of Zernike polynomial being used for reconstructing rabbit corneal surfaces as scanned by the Pentacam segment tomographer, and hence evaluate the accuracy of corneal power maps calculated from such Zernike fitted surfaces. The study utilised a data set of both eyes of 21 rabbits using a reverse engineering approach for deductive reasoning. Pentacam raw elevation data were fitted to Zernike polynomials of orders 2 to 20. The surface fitting process to Zernike polynomials was carried out using randomly selected 80% of the corneal surface data points, and the root means squared fitting error (RMS) was determined for the other 20% of the surface data following the Pareto principle. The process was carried out for both the anterior and posterior surfaces of the corneal surfaces that were measured via Pentacam scans. Raw elevation data and the fitted corneal surfaces were then used to determine corneal axial and tangential curvature maps. For reconstructed surfaces calculated using the Zernike fitted surfaces, the mean and standard deviation of the error incurred by the fitting were calculated. For power maps computed using the raw elevation data, different levels of discrete cosine transform (DCT) smoothing were employed to infer the smoothing level utilised by the Pentacam device. The RMS error was not significantly improved for Zernike polynomial orders above 12 and 10 when fitting the anterior and posterior surfaces of the cornea, respectively. This was noted by the statistically non-significant increase in accuracy when the order was increased beyond these values. The corneal curvature calculations suggest that a smoothing process is employed in the corneal curvature maps outputted by the Pentacam device; however, the exact smoothing method is unknown. Additionally, the results suggest that fitting corneal surfaces to high-order Zernike polynomials will incur a clinical error in the calculation of axial and tangential corneal curvature of at least 0.16 ± 01 D and 0.36 ± 0.02 D, respectively. Rabbit corneal anterior and posterior surfaces scanned via the Pentacam were optimally fitted to orders 12 and 10 Zernike polynomials. This is essential to get stable values of high-order aberrations that are not affected by Zernike polynomial fittings, such as comas for Intracorneal Ring Segments (ICRS) adjustments or spherical aberration for pre-cataract operations. Smoothing was necessary to replicate the corneal curvature maps outputted by the Pentacam tomographer, and fitting corneal surfaces to Zernike polynomials introduces errors in the calculation of both the axial and tangential corneal curvatures. [ABSTRACT FROM AUTHOR]

The aim of this study was to analyse the postoperative corneal cross-linking results of corneal parameters and the ABCD grading system, depending on the cone location. Thirty eyes of 25 patients with keratoconus (KC), who received the corneal cross-linking (CXL) treatment, were included in this study. The exclusion criteria were: patients under 18 years of age, corneal pachymetry less than 400 μm, corneal scarring, history of ocular trauma, history of ocular surgery, and corneal pathology other than KC. Patients were examined at the baseline visit, and followed-up at three, six, and twelve months after the CXL. All patients underwent visual acuity and Scheimpflug tomography at all visits. Progression parameters, keratometries, and ABCD grading were compared between the visits. Patients were classified into two groups: central and paracentral cones group (within the central 5 mm corneal zone) and peripheral cones group (outside the central 5 mm corneal zone), based on X-Y coordinates of maximal keratometry (Kmax). Parameter A remained relatively stable throughout the follow-up period in both groups. Parameter B and parameter C showed a significant increase in both groups postoperatively. Parameter D showed stability at the 6-month post-CXL visit in the peripheral KC group, while the central and paracentral KC group showed improvement at the 12-month post-CXL visit. There was no significant difference in the postoperative response between different cone locations in the ABCD grading system, when classifying according to the Kmax, except an earlier recovery of the parameter D in peripherally located cones. [ABSTRACT FROM AUTHOR]

Purpose: Evaluation of visual and refractive effects of collagen cross-linking (CXL) in progressive keratoconus (KCN). Methods: A total of 95 eyes of 77 patients were retrospectively analyzed. The changes in uncorrected and corrected distance visual acuities (UDVA and CDVA, respectively); spherical or cylindrical refraction and spherical equivalent of refractive error (SPH, CYL, and SE, respectively); central corneal thickness (CCT); and mean keratometry values (K) in the Scheimpflug corneal tomography (Pentacam, Oculus®, Germany) were evaluated at the 1st, 3rd, and 6th post-operative months and the past visit, as compared to pre-operative values. Results: During follow-up, there was a progressive improvement in the mean UDVA and CDVA. Significant improvement was seen in CDVA at the 3rd month (from 0.51±0.23 to 0.59±0.22), in UDVA at the 6th month (from 0.34±0.24 to 0.44±0.25), and in SPH and SE values at the last control (from -2.75±3.50D to -1.92±2.52D for SPH; from -3.51±4.45D to -3.07±3.05D for SE). The mean CCT decreased in the post-operative 1st month and gradually increased in the 3rd and 6th months (from 466.87±63.94 µm to 449.76±50.09 µm, 443.92±42.44 µm, and 454.30±46.86 µm for 1st, 3rd, and 6th months, respectively); almost returned to pre-operative values. There was no significant change in mean CYL and K values throughout the followup (from -2.40±2.11D to -2.45±1.77D for CYL; from 46.89±3.66D to 47.35±5.04D for K). Conclusion: CXL seems to not only slow down the progression of KCN but also improve the visual acuity, which may be a result of ultrastructural changes that occur in the corneal stroma postoperatively, rather than a simple corneal flattening effect. [ABSTRACT FROM AUTHOR]

Keratoconus(KC)is a progressive disease characterized by gradual corneal thinning and ectasia, resulting in irregular astigmatism, myopia, and mild to severe visual impairment. Although the pathogenesis of KC is still unclear, twin studies and family-based studies have identified that the occurrence of KC is closely related to genetic factors. First-degree relatives of KC patients including their parents, siblings and offspring are very important for the family aggregation analysis and polygenic analysis of diseases. This review summarized the current situation of clinical and genetic research about first-degree relatives of KC patients, hoping to deepen the understanding of clinical manifestations and genetic characteristics of first-degree relatives of KC, and to provide new ideas for exploring the role of genetic and environmental factors in the pathogenesis of KC.

Purpose The aim of this study was to evaluate the changes in corneal topography asymmetry indices after corneal collagen cross-linking (CXL) in patients with keratoconus and to analyze their correlation with visual acuity changes and preoperative average keratometric (K) value. Setting and design This is a prospective interventional noncomparative nonrandomized study that was conducted at the Outpatient Clinic of the Ophthalmology Department of Tanta University Hospital. Patients and methods CXL was conducted in 30 eyes of 15 patients with keratoconus. Quantitative descriptors of corneal topography were measured with corneal tomography using a rotating Scheimpflug camera (Pentacam-Oculus). They included seven indices: index of surface variance (ISV), center of keratoconus index (CKI), index of height asymmetry (IHA), index of vertical asymmetry (IVA), keratoconus index (KI), index of height decentration (IHD), and minimum radius of curvature (Rmin). Follow-up of cases was done for 6 months. Results There was a statistically significant improvement in ISV (P0.001). However, the preoperative average K value was not significantly correlated with the improvements in IHA (r=−0,078, P=0.681) and IVA (r=0.204, P=0.280). Conclusion There was a significant improvement in six of the seven topography indices 6 months after CXL. Improvement in these indices was not correlated with corrected distance visual acuity changes. The preoperative average K value was significantly correlated with the improvement in KI, ISV, preoperative IHD, preoperative CKI, and preoperative Rmin.

Objective: To evaluate the corneal topography and tomography of cats using a dual Scheimpflug and Placido disc device. Animal studied: Sixteen mixed‐breed cats (32 eyes). Procedure(s): Cats were sedated using meperidine (4.3 mg/kg/IM) and xylazine (0.5 mg/kg/IM), and evaluated using the software Galilei™. Values assessed included anterior and posterior corneal curvature, total corneal power, and corneal thickness. Results: Ten males and six females aged between 18 and 48 months were evaluated. The simulated keratometry (SimK) was 38.37 ± 0.83D, mean posterior keratometry −4.89 ± 0.34D, and mean total corneal power 38.04 ± 0.94D. The mean central corneal thickness (CCT) was 617.34 ± 53.38 μm with a mean thinnest point of 583.74 ± 60.60 μm. Conclusion: The Galilei™ examination was feasible in cats, enabling a detailed study of the cornea. To the best of our knowledge, this is the first study evaluating the corneal topography and tomography of cats using a device that integrates data from a dual Scheimpflug and Placido disc system. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to validate a blepharo-tensiometer, and investigate the relationship between eyelid pressure (ELP) and corneal tomography/biomechanics., Methods: Repeatability of the blepharo-tensiometer was evaluated at different inclination angles: 10°, 15°, and 20° for the upper eyelid (U10, U15, and U20) and 45°, 50°, and 55° for the lower eyelid (L45, L50, and L55). Reproducibility was evaluated in terms of different operators and inclination angles. Both the maximum and average ELP were evaluated. Best-corrected visual acuity, manifest refraction spherical equivalent, eyelid types, palpebral fissure height, exophthalmometry, axial length, and corneal tomographic/biomechanical parameters were measured. Spearman analysis and generalized estimating equations were used to explore potential correlations., Results: This study included 36 eyes from 36 subjects. The ICCs for repeatability were comparable between different inclination angles, so U15 and L50 were selected for further analysis. The ICCs for reproducibility in terms of different operator or inclination angle also achieved good to excellent outcomes. Certain associations have been revealed between the ELP and corneal tomographic/biomechanical parameters. Tomographically, ELP influences corneal front J0, front asphericity, and the index of surface variance; whereas biomechanically, ELP affects the time at first applanation, deformation amplitude at highest concavity, and biomechanically corrected intraocular pressure., Conclusions: The tensiometer showed good precision. The study also showed that ELP causes a flattening effect on the peripheral cornea, with greater ELP linked to better corneal biomechanical properties in healthy subjects. These findings may potentially illuminate new avenues in the field of corneal disorders and beyond., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.)