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A patient presented with corneoscleral thinning five months after the treatment of suspected ocular squamous surface neoplasia with mitomycin-C and interferon. For tectonic and aesthetic purposes, we decided to perform lamellar corneoscleral transplantation. The approach used established new tectonic support and corneal homeostasis. This technique might be an option in similar cases.

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Purpose: Brown-McLean syndrome (BMS) is a clinical condition characterized by peripheral corneal edema with central corneal transparency. This study aims to document the tomographic and biomechanical characteristics of 3 patients with typical BMS features using the Pentacam® AXL and CORVIS ST® (Oculus Optikgeräte GmbH, Wetzlar, Germany). Observations: Three cases of BMS are presented. Case 1 involves a 26-year-old male, Case 2 a 55-year-old male, and Case 3 a 74-year-old male. The patients in Cases 1 and 3 had bilateral BMS, while the patient in Case 2 had BMS in the right eye and aphakic bullous keratopathy in the left eye. All three patients were aphakic following cataract surgery. Notably, Cases 1 and 2 were first-degree relatives (son and father), both with bilateral microspherophakia and resultant bilateral aphakia from pediatric cataract surgery. Tomographic analysis revealed a consistent increase in corneal thickness from the center to the periphery in BMS eyes, marked by an abrupt rise in the corneal thickness spatial profile (CTSP) and percentage thickness increase (PTI) curves from the thinnest point towards the periphery. There was no loss of parallel isopachs, no displacement of the thinnest point of the cornea, and no evidence of focal posterior corneal surface depression, typical signs of generalized corneal edema. Biomechanically, BMS eyes exhibited relatively normal corneal stiffness, integrated radius, Ambrósio's relational thickness to the horizontal profile (ARTh), and maximum deformation amplitude ratio at 2mm from the corneal apex (DA ratio). However, the left eye of the patient in Case 2, which had aphakic bullous keratopathy, showed altered biomechanical parameters indicative of a softer cornea with loss of rigidity. Conclusions and importance: This case series is the first to evaluate the biomechanical and tomographic features of eyes with BMS. Despite the abrupt rise in CTSP and PTI curves from the thinnest point towards the periphery, the relatively normal central corneal biomechanical indices in these BMS eyes are expected when edema is limited to the periphery. These indices become abnormal when there is progression to central corneal edema with bullous keratopathy.

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Introduction: The purpose of this clinical report was to describe an unprecedented case of bilateral pressure-induced stromal keratopathy (PISK) following corneal photorefractive keratectomy, associated with presumed herpetic keratitis, and to present tomographic and biomechanical findings before and after appropriate treatment. Case Presentation: A 33-year-old male patient was referred to our clinic with suspected delayed corneal epithelial healing 3 weeks after an uncomplicated PRK. A central layer of corneal opacity with a presumed fluid-filled interface area was observed upon slit lamp biomicroscopy. Scheimpflug images from the Pentacam® revealed a hyperreflective area beneath the central cornea. Scheimpflug-based corneal tomography, biomechanical assessment using the Pentacam® AXL Wave, and the Corvis ST® were conducted. Goldmann applanation tonometry measured 23/13 mm Hg, while noncontact tonometry intraocular pressure measured with the Corvis ST® (Corvis ST IOPnct) was 40.5/43.5 mm Hg. Treatment with oral valacyclovir, combined with ocular hypotensive therapy, led to a significant reduction in IOP and improved corneal deformation parameters after 1 month. Conclusion: Surgeons should be aware of the inaccuracy of Goldmann applanation tonometry in PISK, which can occur after LASIK or surface ablation.

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PURPOSE: This article introduces the Pentacam® Cornea OCT (optical coherence tomography). This advanced corneal imaging system combines rotating ultra-high-resolution spectral domain OCT with sub- 2-micron axial resolution and Scheimpflug photography. The purpose of this study is to present the first experience with the instrument and its potential for corneal diagnostics, including optical biopsy. METHODS: In this prospective study, the Pentacam® Cornea OCT was used to image the corneas of seven patients. The novel wide-angle pericentric scan system enables optimal OCT imaging performance for the corneal layer structure over the entire width of the cornea, including the limbal regions. A detailed analysis of the resulting images assessed the synergism between the OCT and Scheimpflug photography. RESULTS: The Pentacam® Cornea OCT demonstrated significantly improved image resolution and ability to individualize corneal layers with high quality. There is a synergism between the OCT high-definition signal to individualize details on the cornea and Scheimpflug photography to detect and quantify corneal scattering. The noncontact exam was proven safe, user-friendly, and effective for enabling optical biopsy. CONCLUSIONS: Pentacam® Cornea OCT is an advancement in corneal imaging technology. The ultra-high-resolution spectral domain OCT and Scheimpflug photography provide unprecedented detail and resolution, enabling optical biopsy and improving the understanding of corneal pathology. Further studies are necessary to compare and analyze the tomographic reconstructions of the cornea with the different wavelengths, which may provide helpful information for diagnosing and managing corneal diseases.

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INTRODUCTION: The study aims to demonstrate and estimate the prevalence of clinical corneal ectasia and keratoconus (KC) in patients with relatively low keratometry (low-K KC). METHODS: In a retrospective, analytical, and non-interventionist study, one eye was randomly selected from 1054 patients from the original Tomographic Biomechanical Index (TBIv1) study and the external validation (from Rio de Janeiro, Brazil, and Milan, Italy clinics). Patients were stratified into three groups. Group 1 included 736 normal patients, and groups 2 and 3 included 318 patients with clinical KC in both eyes, divided into low-K KC (90 patients) and high-K KC (228 patients), respectively. All patients underwent a comprehensive ophthalmological evaluation along with Pentacam and Corvis ST (Oculus, Wetzlar, Germany) examinations. Cases with maximum mean zone 3 mm keratometry (Kmax zone mean 3 mm) lower than 47.6 diopters (D) were considered as low-keratometry keratoconus, and cases with Kmax zone mean 3 mm higher than 47.6 D were regarded as high-keratometry keratoconus. RESULTS: Ninety (28.30%) of the 318 KC group presented ectasia with low-keratometric values (low-Kmax). The average age in the normal group was 39.28 years (range 6.99-90.12), in the low-Kmax KC group it was 37.49 (range 13.35-78.45), and in the high-Kmax KC group it was 34.22 years (range 12.7-80.34). Mean and SD values and median (range), respectively, of some corneal tomographic and biomechanical parameters evaluated from the low-Kmax KC group were as follows: Belin-Ambrósio enhanced ectasia display (BAD-D) 3.79 ± 1.62 and 3.66 (0.83-9.73); Pentacam random forest index (PRFI) 0.78 ± 0.25 and 0.91 (0.05-1); corneal biomechanical index (CBI) 0.58 ± 0.43 and 0.75 (0-1); TBI 0.93 ± 0.17 and 1 (0.35-1); and stiffness parameter at A1 (SP-A1) 86.16 ± 19.62 and 86.05 (42.94-141.66). CONCLUSION: Relatively low keratometry, with a Kmax lower than 47.6 D, can occur in up to 28.30% of clinical keratoconus. These cases have a less severe presentation of the disease. Future studies involving larger populations and prospective designs are necessary to confirm the prevalence of keratoconus with low keratometry and define prognostic factors in such cases.

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The study of corneal biomechanics has become relevant in recent years due to its possible applications in the diagnosis, management, and treatment of various diseases such as glaucoma, keratorefractive surgery and different corneal diseases. The clinical biomechanical investigation has become of great importance in the setting of refractive surgery to identify patients at higher risk of developing iatrogenic ectasia. This review focuses on two of the technologies available for clinical use, the Ocular Response Analyzer (Reichert Ophthalmic Instruments, Buffalo, NY, USA) and the Corvis ST (Oculus Optikgergäte GmbH, Wetzlar, Germany). Both are non-contact tonometers that provided a clinical evaluation of corneal biomechanics. The fundamentals and main parameters of each device are described, as well as their use in eye surgery and the corneal biomechanical behavior in eye diseases. Finally, we will discuss the more recent Brillouin microscopy biomechanical analysis, and the integration Scheimpflug-based corneal tomography and biomechanical data with artificial intelligence to increase accuracy to detect risk of ectasia.

El estudio de la biomecánica corneal ha cobrado relevancia en los últimos años debido a sus posibles aplicaciones en el diagnóstico, el manejo y el tratamiento de diversas enfermedades, como glaucoma, cirugía queratorrefractiva y diferentes enfermedades corneales. La investigación de la biomecánica corneal es de mucha importancia en el contexto de cirugía refractiva, pues podría identificar pacientes en riesgo de desarrollar una ectasia corneal iatrogénica. Esta revisión se centra en dos de las tecnologías disponibles para uso clínico: el Ocular Response Analyzer (Reichert Ophthalmic Instruments, Buffalo, NY, EE. UU.) y el Corvis ST (Oculus Optikgergäte GmbH, Wetzlar, Alemania). Ambos son tonómetros de no contacto que proporcionan una evaluación clínica de la biomecánica corneal. Se describen los fundamentos y los principales parámetros de cada dispositivo, así como su uso en cirugía ocular y el comportamiento biomecánico corneal en las enfermedades oculares. Finalmente, se mencionan los dispositivos más recientes de análisis biomecánico, como la microscopía de Brillouin, así como la integración de los datos biomecánicos y topográficos basados en Scheimpflug con la inteligencia artificial para aumentar la precisión en la detección del riesgo de ectasias.

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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.

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

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Biomechanics is a branch of biophysics that deals with mechanics applied to biology. Corneal biomechanics have an important role in managing patients with glaucoma. While evidence suggests that patients with thin and stiffer corneas have a higher risk of developing glaucoma, it also influences the accurate measurement of intraocular pressure. We reviewed the pertinent literature to help increase our understanding of the biomechanics of the cornea and other ocular structures and how they can help optimize clinical and surgical treatments, taking into consideration individual variabilities, improve the diagnosis of suspected patients, and help monitor the response to treatment.

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PURPOSE: To test the ability of the corneal epithelial pattern standard deviation (PSD) to distinguish between normal and cases with corneal ectatic condition. SETTING: Instituto de Olhos Renato Ambrósio, Rio de Janeiro, Brazil. DESIGN: Cross-sectional retrospective study. METHODS: Patients were stratified into 4 groups based on clinical data and corneal tomography. Groups 1 and 2 comprised 1 eye randomly selected from 105 patients with normal corneas (N) and 86 patients with bilateral keratoconus (KC). Groups 3 and 4, respectively, comprised 11 ectatic eyes with no surgical treatment for KC (very asymmetric ectasia [VAE]-E) from patients whose fellow eyes (61) presented with normal topographic patterns (VAE-NT). Corneas were scanned using an OCT system (RT Vue) and Scheimpflug corneal tomography (Pentacam) and also had biomechanical assessment through the Corvis ST. Corneal epithelial thickness maps were analyzed, and the PSD value was calculated. The area under the receiver operating characteristic curve analysis was used to evaluate the diagnostic accuracy of the indices. RESULTS: A total of 105 normal eyes, 86 keratoconic eyes, and 11 ectatic eyes whose fellow eyes (61) presented normal topographic patterns were evaluated. Epithelial PSD was significantly different across the 4 groups ( P < .0001). The pairwise comparison revealed that the normal group presented significantly lower values than both ectasia groups (KC and VAE-E, P < .0001) and the VAE-NT group ( P = .0008). There was no statistical significant difference between KC and VAE-E ( P = .4284), while they were significantly higher than the VAE-NT group ( P < .0001 and P = .0004). CONCLUSIONS: Epithelial PSD can be used to detect abnormal epithelial thickness patterns. Corneal epithelial thickness changes could be detected accurately in patients with KC, even in the form fruste of the disease.

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Purpose: To prospectively review the importance of biomechanical assessment in the screening, diagnosis, prognosis, individualized planning, and clinical follow-up for ectatic corneal diseases.Methods: We demonstrate two commercially available devices to assess the corneal biomechanics in vivo, the Ocular Response Analyzer (ORA, Reichester, NY, USA) and the Corvis ST (Oculus, Wetzlar, Germany). Novel devices have been demonstrated to provide in vivo biomechanical measurements, including Brillouin optical microscopy and OCT elastography. Conclusion: The integration of biomechanical data and other data from multimodal refractive imaging using artificial intelligence demonstrated the ability to enhance accuracy in diagnosing ectatic corneal diseases.

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There are different fundamental diagnostic strategies for patients with ectatic corneal diseases (ECDs): screening, confirmation of the diagnosis, classification of the type of ECD, severity staging, prognostic assessment, and clinical follow-up. The conscious application of such strategies enables individualized treatments. The need for improved diagnostics of ECD is related to the advent of therapeutic refractive procedures that are considered prior to keratoplasty. Among such less invasive procedures, we include corneal crosslinking, customized ablations, and intracorneal ring segment implantation. Besides the paradigm shift in managing patients with ECD, enhancing the sensitivity to detect very mild forms of disease, and characterizing the inherent susceptibility for ectasia progression, became relevant for identifying patients at higher risk for progressive iatrogenic ectasia after laser vision correction (LVC). Moreover, the hypothesis that mild keratoconus is a risk factor for delivering a baby with Down's syndrome potentially augments the relevance of the diagnostics of ECD. Multimodal refractive imaging involves different technologies, including Placido-disk corneal topography, Scheimpflug 3-D tomography, segmental or layered tomography with layered epithelial thickness using OCT (optical coherence tomography), and digital very high-frequency ultrasound (VHF-US), and ocular wavefront. Corneal biomechanical assessments and genetic and molecular biology tests have translated to clinical measurements. Artificial intelligence allows for the integration of a plethora of clinical data and has proven its relevance in facilitating clinical decisions, allowing personalized or individualized treatments.

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Purpose: The ability to predict corneal edema and understand its relationship with imaging parameters enables optimization of decision-making in terms of cataract surgery. Therefore, we aimed to elucidate the immediate tomographic alterations after phacoemulsification. Patients and Methods: In this prospective study, we evaluated clinical and corneal tomographic data of 30 patients with cataracts, obtained using a rotating Scheimpflug tomographic system before and after cataract surgery with a phacoemulsification system. Corneal thickness and volume were measured, and Pentacam Nucleus Staging, keratometry, and specular microscopy were performed preoperatively and immediately postoperatively. The Wilcoxon signed-rank test was used to compare pre-and postoperative values. We calculated the correlations between the changes in these values and multiple parameters related to phacodynamics, including "ultrasound (US) elapsed" (phaco time), "US average" (average power used), and "US absolute" (energy effectively dissipated, a product of the other two parameters). Results: There were increases in corneal volume (p<0.0001) and pachymetry (p<0.0001), and a decrease in endothelial cell count (p<0.0001) after surgery. The mean differences in pre- and postoperative specular microscopy, corneal volume, and pachymetry were -335.13±236.21 cells/mm3, 1.33±0.56 mm3, and 61.33±23.73 microns, respectively. The difference in pre-and postoperative corneal volume in patients with US elapsed ≥40 s was 0.75 mm3 greater than that in patients with US elapsed <40 s (95% confidence interval [CI]: 0.24-1.25; p=0.005); that of pachymetry in patients with US elapsed ≥40 s was 31.76 microns greater than that in patients with US elapsed <40 s (95% CI: 9.55-53.97; p=0.007). Spearman correlation revealed that, for every 1% increase in cataract density, the US average value increased by 0.31% (coef.: 0.3110; 95% CI: 0.0741-0.5490; p=0.012). Conclusion: Knowledge of Pentacam Nucleus Staging and the effect of US elapsed on differences in corneal volume and pachymetry before and after cataract surgery should be of particular value for surgeons who routinely encounter patients with hard cataracts.

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Keratoconus (KC) is likely to be more aggressive in the pediatric population, with a higher risk of progression and visual loss. Several techniques have been proposed for corneal crosslinking (CXL) so far. The standard CXL (SCXL) technique, or the Dresden Protocol, originally developed by Wollensak et al., has been shown to be safe and effective in the pediatric KC group. With similar efficacy to the conventional method, the accelerated CXL (ACXL) protocols proposed a reduced UVA exposure time by increasing the intensity of UVA irradiation. Transepithelial CXL (TCXL), considered an "epithelium-on" method, emerged as a strategy to improve safety and reduce postoperative complications and discomfort. For thinner corneas, we can highlight the use of hypoosmolar riboflavin and new studies, such as contact lens-assisted CXL (CACXL), the epithelial-island CXL (EI-CXL), and the Sub400 protocol. In addition to the different protocols used, another factor that changes CXL results is the type of carrier used: dextran-based or hydroxypropyl methylcellulose-based (HPMC) riboflavin solutions. There are several ways to perform a CXL surgery, and it is still unclear which method is the safest and most effective in the pediatric group. This review of the literature in English, available in PubMed, provides an update on corneal CXL in the pediatric KC group, exploring the data on the techniques currently used and under investigation, including their advantages, efficacy, safety profiles, risks, and cost analyses.

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PURPOSE: To evaluate the characteristics of corneal material properties in healthy individuals and keratoconic patients using the stress-strain index (SSI). SETTING: Vincieye Clinic in Milan, Italy, and Instituto de Olhos Renato Ambrósio in Rio de Janeiro, Brazil. DESIGN: Retrospective observational cross-sectional study. METHODS: Records of 1221 patients were divided into 3 groups: healthy corneas (n = 728), bilateral keratoconus (KC, n = 388), and very asymmetric ectasia (VAE, n = 105) when patients presented with clinical ectasia in 1 eye and normal topography (VAE-NT) in the fellow eye. All patients were examined with Pentacam HR and Corvis ST. Severity of KC cases was stratified according to the Pentacam topographic KC classification. The SSI distribution across the different groups and its correlation with age, biomechanically corrected intraocular pressure (bIOP), and central corneal thickness (CCT) were assessed. RESULTS: A statistically significant difference between healthy individuals and each of the keratoconic groups ( P < .001) was observed, and a progressive reduction in the SSI was observed across the groups. A significant correlation was observed between the SSI and age in all groups ( P < .010) but KC severe subgroup ( P = .361). No correlation between the SSI and bIOP and CCT was observed in all KC subgroups and VAE-NT groups ( P > .050). Among healthy eyes, there was only a mild correlation between the SSI and bIOP ( R = 0.12, P = .002) and CCT ( R = 0.13, P = .001). CONCLUSIONS: This study estimates the in vivo corneal material properties in healthy individuals and patients with KC using a new method. The SSI showed a progressive deterioration within the advance in disease stages while being relatively independent of bIOP and CCT but positively correlated with age.

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PURPOSE: To evaluate correlation between Placido-disc and rotating Scheimpflug keratometric findings in children with progressive keratoconus (KC) before and after corneal crosslinking (CXL) and investigate whether these limits of agreement varied according to disease severity. SETTING: Department of Ophthalmology of São Paulo Hospital, São Paulo, Brazil. DESIGN: Prospective nonrandomized open study. METHODS: Data obtained using rotating Scheimpflug-based tomography and Placido-disc-based topography devices were collected from preoperative and last follow-up postoperative children with KC operated on using standard CXL protocol. Correlation and agreement analyses were performed between the 2 devices before and after CXL to obtain keratometric (K) findings. RESULTS: 44 eyes from 44 patients aged 8 to 16 years were analyzed at all timepoints. All parameters were found to be strongly correlated before ( r = 0.84 to 0.99, P < .001) and after ( r = 0.93 to 0.99, P < .001) CXL. The mean Scheimpflug measurements of flat K, steep K, Kmax, mean K, and corneal astigmatism were higher than Placido-disc measurements in a preoperative period. This mean difference decreased in postoperative, but, with exception of Kmax and corneal astigmatism, Scheimpflug measurements remained higher. The mean parameter measurements from both devices decreased after CXL; 95% limits of agreement between instruments were wide for all parameters and decreased in postoperative and in mild KC. CONCLUSIONS: Keratometry measurements obtained using rotating Scheimpflug and Placido-disc technology were found to be closely correlated but not interchangeable before and after CXL in pediatric patients. Agreement between devices was better after CXL and in mild KC than in advanced KC.

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PURPOSE: This retrospective cross-sectional study evaluated the potential of an additional biomechanical parameter 'E' as an addition to the tomographic ABCD ectasia/keratoconus (KC) staging. METHODS: The Corvis Biomechanical Factor (CBiF) represents the modified linear term of the Corvis Biomechanical Index (CBI) developed based on 448 KC corneas from the Homburg Keratoconus Center (HKC). The CBiF range was divided into five stages (E0 to E4) to create a grading system according to the ABCD stages. Stage E0 was characterized by values smaller than the 2.5 percentile. The thresholds were created by dividing the CBiF range between the 2.5 and 97.5 percentiles into four groups of equal values (E1-E4). The frequency distribution of 'E' was analysed and independently validated based on another 860 KC corneas dataset from Milano and Rio de Janeiro (MR). The relationship between 'E' and the ABCD staging was analysed by cross-tabulation. The specificity of 'E' was assessed based on healthy controls (112|851) from both datasets (HKC|MR). RESULTS: 'E' was normally distributed with E0 = 37|30, E1 = 86|200, E2 = 155|354, E3 = 101|206, E4 = 69|70 in the KC group and 96.4%|90.5% of the controls classified E0 in the HKC|MR dataset, respectively. Cross-tabulation revealed that 'E' was most comparable to posterior corneal curvature ('B') in both datasets, while showing a trend towards more advanced stages in comparison to anterior corneal curvature ('A') and thinnest corneal thickness ('C'). CONCLUSION: The novel Corvis-derived parameter 'E' provides a biomechanical staging for ectasia/KC potentially enhancing the ABCD staging and may detect abnormalities before tomographic changes, which requires further studies.

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OBJECTIVE: Evaluation of central corneal densitometry changes following Ferrara corneal ring segment implantation in patients with keratoconus, especially the correlation between corneal densitometry and keratometry. METHODS: Retrospective, non-comparative, interventional study based on the review of medical records of patients diagnosed with keratoconus who underwent Ferrara corneal ring segment implantation. Pre and post-operative corneal densitometry measurements obtained with Pentacam HR (Oculus, Wetzlar, Germany) were analyzed. The follow-up time was 3 months, and data comparison was made, using specific statistical analysis, with the data of 3 months postoperatively. RESULTS: The study sample consisted of 43 eyes of 36 patients. The mean corrected visual acuity improved from 0.82 LogMAR preoperatively (SD ± 0.33) to 0.19 LogMAR (SD ± 0.13) postoperatively. The mean spherical equivalent varied from -4.63 (SD ± 3.94) preoperatively to -2.16 (SD ± 2.63) postoperatively. Asphericity varied from -0.69 (SD ± 0.32) preoperatively to -0.27 (SD ± 0.31) postoperatively. The mean maximum K was 54.01D (SD ± 3.38) preoperatively and 51.50D (SD ± 2.90) postoperatively. The mean anterior densitometric value was 18.26 (SD ± 2.03) preoperatively and 17.66 (SD ± 1.84) postoperatively. CONCLUSION: Corneal densitometry is an interesting technology that should be studied in keratoconus patients. Our results suggest that the corneal densitometry in the cornea's anterior layer reduces after ICRS implantation and correlates with corneal keratometry. Further studies should be performed to increase the knowledge in this field.

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To report a case of a 20-year-old woman who developed massive and progressive corneal remodeling in both eyes after bilateral PRK with mitomycin and CXL as an elective refractive procedure for mild keratoconus. The patient had 6 years of follow up, initially presenting with focal steepening of up to 20 diopters on both eyes one-and-a-half- years postoperatively that spontaneously reversed over the next five years while the high order aberrations worsened. At the present time, the patient depends on bilateral scleral contact lenses for her day-to-day activities. The use of combined elective PRK with mitomycin and prophylactic CXL could lead to progressive corneal deformation. Additional reports would help to establish the role of this combination procedure among the armamentarium to visually rehabilitate patients with keratoconus.

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