Longitudinal Evaluation of Biomechanical Indices in Fellow Eyes of Patients With Keratoconus Classified as Having Very Asymmetric Ectasia With Normal Topography.

PURPOSE: To evaluate the biomechanical longitudinal variability and progression of tomographically normal fellow eyes of patients with keratoconus. METHODS: Of 513 patients with keratoconus, 30 patients with tomographically normal fellow eyes were included in this study. Tomographic and biomechanical parameters of the Pentacam and Corvis ST (Oculus Optikgeräte GmbH) were analyzed in multiple follow-up examinations, including the ABCD grading, Belin/Ambrósio Enhanced Ectasia total deviation index (BAD-D), Corvis Biomechanical Index (CBI), Corvis Biomechanical Factor (CBiF), and Tomographic and Biomechanical Index (TBI). A mixed regression model was applied. The results were compared to a healthy control group (n = 17) and a keratoconus group (n = 20). RESULTS: Within a maximum observation period of 3.3 years, no fellow eye (0%) showed a progression to tomographically evident keratoconus. No significant change in tomographic or biomechanical parameters was detected over the study period. The indices BAD-D, CBI, CbiF, and TBI exhibited a certain variability over time, whereas the tomographic ABC parameters and maximum keratometry barely changed. This was also shown in the control group and for all parameters in the keratoconus group, except the TBI. CONCLUSIONS: During the observation period none of the normal fellow eyes progressed to tomographically detectable keratoconus. However, biomechanical parameters CBI, CbiF, and TBI showed pathological values in 43.3% of eyes and certain variability. Subsequent studies with a longer observation period are warranted to confirm the biomechanical trends seen in this study and to rate the ability of single measurements to diagnose early keratoconus. [J Refract Surg. 2024;40(1):e48-e56.].

Idiopathic dilatation of the submandibular gland duct.

Lithiasis and stenosis may cause salivary duct dilatation due to the increased pressure in the duct upstream of the obstruction. Idiopathic dilatations, also called megaducts, with no associated increase in pressure, have only been described in the parotid gland. The aim of this study was to describe the characteristics of submandibular duct dilatation unrelated to lithiasis, stenosis, or an imperforate duct, to report the existence of submandibular megaducts. This retrospective single-centre study included patients treated at La Conception University Hospital, Marseille, France, between 2007 and 2019. Patients with submandibular duct dilatation of ≥4 mm confirmed by magnetic resonance imaging sialography (sialo-MRI), who also underwent sialendoscopy to identify any associated stenosis, were included. Patients with lithiasis, stenosis, an imperforate ostium, or a history of trauma or surgery to the floor of the mouth were excluded. Five patients (three female, two male) aged 30-76 years with idiopathic duct dilatations in nine submandibular glands were included. The most commonly reported symptoms were submandibular swelling, pruritus, and discomfort, mostly outside mealtimes. Recurrence of symptoms after treatment was frequent. This study is novel in describing submandibular megaducts as opposed to dilatation caused by high pressure associated with stenosis, with confirmation by sialo-MRI and sialendoscopy.

Corneal topometric indices and proclivity toward corneal ectasia in vernal keratoconjunctivitis.

PURPOSE: To investigate changes in topometric corneal indices and proclivity toward corneal ectasia, as well as keratometric indices and anterior chamber dimensions in palpebral vernal keratoconjunctivitis (VKC). METHODS: This study included 80 patients with clinically established symptoms of grade 0 or grade 1 palpebral VKC (group 1) and 66 healthy participants (group 2). After a comprehensive ophthalmic examination including best-corrected visual acuity, intraocular pressure measurements and slit-lamp biomicroscopy, pachymetric indices and anterior chamber dimensions were measured using the Pentacam HR rotating Scheimpflug device. Topometric indices, which are particularly useful for determining proclivity toward corneal ectasia, were extracted from a topometric map. RESULTS: In groups 1 and 2, the mean ages were 13.11±5.22 and 16.45±5.09 years, respectively. The mean age at disease onset in group 1 was 10.09±5.03 years, and the mean disease duration was 36.23±8.43 months. Group 1 had significantly higher mean topometric indices than group 2, particularly the index of surface variance (P=0.001), index of vertical asymmetry (P=0.007), center keratoconus index (P=0.050), and Belin/Ambrosio enhanced ectasia total deviation value (P=0.032). Mean posterior corneal astigmatism differed significantly between groups 1 and 2 (P=0.003). CONCLUSIONS: Significantly higher mean topometric indices in VKC indicate a proclivity for corneal ectasia, which could be attributed to general changes in the corneal ultrastructure caused by persistent itching-induced eye rubbing.

Idiopathic Dilatation of the Right Atrium: Diagnosis and Management.

Idiopathic dilatation of the right atrium is a rare condition with an unknown etiology. It is characterized by a significant enlargement of the right atrium without the presence of other valvopathies, intracardiac shunts, or pulmonary hypertension. This report presents the case of a 50-year-old woman with a significantly enlarged right atrium that was identified at birth; however, a definitive diagnosis was made later in life. The patient did not have any genetic diseases. Through the help of regular follow-up, anticoagulant therapy, previous radio-frequency ablation, and antiarrhythmic medications, she was able to carry a pregnancy to full term and live a regular life.

[A severe unilateral corneal ectasia in children]. / Une ectasie cornéenne sévère unilatérale de l'enfant.

PURPOSE: We report a case of unilateral Terrien's marginal degeneration in a 14-year-old girl. CLINICAL CASE: Slit-lamp examination of the affected eye revealed 360° circumferential lipid deposits with 6mm of superior limbal distension, superficial neovascularization, a zone of corneal thinning from 3:00 to 9:00 with a zone of corneomalacia at 11:00. The remainder of the cornea was clear, without fluorescein staining or anterior chamber reaction. DISCUSSION: Terrien's marginal degeneration (TMD) is typically known to occur bilaterally in men over the age of 40. Terrien's degeneration must be differentiated from other causes of peripheral corneal thinning; the primary differential diagnosis is Fuchs' marginal keratitis. Other causes of corneal thinning must be ruled out, including Mooren's ulcer. In Terrien's degeneration, there is no central mined edge in the thinning sulcus, the epithelium remains intact, and affected patients do not present with pain. Other differential diagnoses include pellucid marginal degeneration and sulcus degeneration, which are characterized by the absence of lipid infiltrates associated with the central region of the thinning zone, thus distinguishing them from TMD. CONCLUSION: It is important to keep in mind that Terrien's marginal degeneration can occur in children.

Corneal ectasia following photorefractive keratectomy: a confocal microscopic case report and literature review.

The occurrence of corneal ectasia after photorefractive keratectomy is a rare but serious complication of refractive surgery. Possible risk factors are not well assessed, but a probable reason is the failure to detect keratoconus preoperatively. In this report, we describe a case of corneal ectasia after photorefractive keratectomy in a patient who presented a suspicious tomography pattern preoperatively but had no degenerative alterations associated with pathologic keratoconus, as revealed by in vivo corneal confocal microscopy. We also review eligible case reports of post-photorefractive keratectomy ectasia to find similar characteristics.

Crosslinking for post-laser-assisted in situ keratomileusis corneal ectasia: Transepithelial flap-on 30 minute and flap-lift 4 minute protocol.

Purpose: To evaluate the outcomes of transepithelial corneal collagen crosslinking (CXL) for management of corneal ectasia after laser-assisted in situ keratomileusis (LASIK). Methods: CXL was performed on 18 eyes of 16 patients either with LASIK flap lift (n = 9; 365 nm, 30 mW/cm2, 4 minutes, pulse) or with transepithelial flap-on (n = 9 eyes; 365 nm, 3 mW/cm2, 30 minutes) technique. Postoperative change in maximum keratometry (Kmax), anterior elevation, posterior elevation, spherical equivalent (SE), logMAR uncorrected distance visual acuity (UDVA), aberrations, and central corneal thickness (CCT) were evaluated at 12 months postoperatively. Results: A total of 18 eyes of 16 patients (11 males, 5 females) were included. Overall, Kmax flattened more after flap-on CXL (P = 0.014) compared to flap-lift CXL. The endothelial cell density and posterior elevation were stable throughout the follow-up period. Index of vertical asymmetry (IVA), keratoconus index (KI), and central keratoconus index (CKI) decreased after flap-on CXL at 12 months, postoperatively (P < 0.05), whereas there were no statistically significant changes in these parameters after flap-off CXL group. The spherical aberrations and total root mean square decreased after flap-lift CXL at 12 months, postoperatively (P < 0.05). Conclusion: In our study, transepithelial collagen crosslinking was successfully used to halt disease progression in post-LASIK keratectasia. We recommend flap-on surgical technique for these cases.

Comparison of Ectasia Detection in Early Keratoconus Using Scheimpflug-Based Corneal Tomography and Biomechanical Assessments.

PURPOSE: The aim of this study was to determine the detection of keratoconus using corneal biomechanical parameters only, a corneal tomographic parameter only, and a parameter that combines corneal biomechanical and tomographic indices. METHODS: The discriminatory power of the Pentacam Random Forest Index (PRFI), Belin/Ambrósio Enhanced Ectasia Display (BAD-D) index, Corvis Biomechanical Index (CBI), and Tomographic and Biomechanical Index (TBI) to differentiate between normal eyes (n = 84), eyes with very asymmetric corneal ectasia (VAE-E, n = 21), and the fellow eyes without apparent ectasia based on normal tomography (VAE-NT, n = 21) was assessed. Statistical analyses were completed with R software using t -tests, Wilcoxon rank sum tests, and receiver operating characteristic (ROC) curves. The DeLong test was used to compare the area under the ROC curve (AUROC). RESULTS: The TBI and PRFI had the highest AUROC when distinguishing between normal and VAE-E corneas (AUROC = 1.00, 95% CI = 1.00-1.00); however, they were not statistically superior to the CBI (AUROC = 0.97, P = 0.27) or BAD-D (AUROC = 1.00, P = 0.34). The TBI (AUROC = 0.92, 95% CI = 0.86-0.98) was superior to CBI (AUROC = 0.78, P = 0.02) and BAD-D (AUROC = 0.81, P = 0.02) when distinguishing between healthy and VAE-NT corneas. At a threshold of 0.72, the TBI had 99% sensitivity, 67% specificity, and 92% accuracy in distinguishing normal and VAE-NT corneas. CONCLUSIONS: The TBI is a useful parameter for the screening of subclinical and frank keratoconus in tomographically normal eyes.

Comprehensive management of post-LASIK ectasia: From prevention to treatment.

Post-laser in situ keratomileusis (post-LASIK) ectasia (PLE) is one of the most serious complications after refractive surgery, mainly manifested as progressive thinning and trembling thinning of the cornea, accompanied by increased myopia and astigmatism. The mechanisms behind mainly include genetic risk factors and external environmental factors such as eye rubbing and cornea surgery. In order to achieve the goal of reducing the incidence of ectasia, preoperative screening strategies need to be continuously improved, through the collection and assessment of genetic and environmental risk factors. Although previous preoperative screening methods did not have a uniform standard, the emergence of artificial intelligence (AI) can help us process a large amount of information and make rational use of the data. By using high-fidelity finite element modelling, differences in preoperative and postoperative strain distributions can be observed, which can predict the risk of postoperative ectasia. In this review, we describe the incidence, aetiology, prevention and treatment of PLE for the purpose of comprehensive management. In terms of treatment, corneal collagen cross-linking has been widely used to treat progressive keratoconus and other ectasia disease, either as a preventive measure during surgery or as a therapeutic modality after surgery to prevent progression of corneal dilation. Although the standard Dresden protocol has been identified as the gold standard treatment for corneal dilatation, a series of refinements, investigations and long-term studies have been conducted in recent years. Thus, understanding the factors involved in delaying the onset and slowing progression of cornea ectasia will be key to reducing the incidence worldwide.

Optimized Artificial Intelligence for Enhanced Ectasia Detection Using Scheimpflug-Based Corneal Tomography and Biomechanical Data.

PURPOSE: To optimize artificial intelligence (AI) algorithms to integrate Scheimpflug-based corneal tomography and biomechanics to enhance ectasia detection. DESIGN: Multicenter cross-sectional case-control retrospective study. METHODS: A total of 3886 unoperated eyes from 3412 patients had Pentacam and Corvis ST (Oculus Optikgeräte GmbH) examinations. The database included 1 eye randomly selected from 1680 normal patients (N) and from 1181 "bilateral" keratoconus (KC) patients, along with 551 normal topography eyes from patients with very asymmetric ectasia (VAE-NT), and their 474 unoperated ectatic (VAE-E) eyes. The current TBIv1 (tomographic-biomechanical index) was tested, and an optimized AI algorithm was developed for augmenting accuracy. RESULTS: The area under the receiver operating characteristic curve (AUC) of the TBIv1 for discriminating clinical ectasia (KC and VAE-E) was 0.999 (98.5% sensitivity; 98.6% specificity [cutoff: 0.5]), and for VAE-NT, 0.899 (76% sensitivity; 89.1% specificity [cutoff: 0.29]). A novel random forest algorithm (TBIv2), developed with 18 features in 156 trees using 10-fold cross-validation, had a significantly higher AUC (0.945; DeLong, P < .0001) for detecting VAE-NT (84.4% sensitivity and 90.1% specificity; cutoff: 0.43; DeLong, P < .0001) and a similar AUC for clinical ectasia (0.999; DeLong, P = .818; 98.7% sensitivity; 99.2% specificity [cutoff: 0.8]). Considering all cases, the TBIv2 had a higher AUC (0.985) than TBIv1 (0.974; DeLong, P < .0001). CONCLUSIONS: AI optimization to integrate Scheimpflug-based corneal tomography and biomechanical assessments augments accuracy for ectasia detection, characterizing ectasia susceptibility in the diverse VAE-NT group. Some patients with VAE may have true unilateral ectasia. Machine learning considering additional data, including epithelial thickness or other parameters from multimodal refractive imaging, will continuously enhance accuracy. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.

Analysis of the diagnostic accuracy of Belin/Ambrósio Enhanced Ectasia and Corvis ST parameters for subclinical keratoconus.

OBJECTIVE: To investigate the diagnostic accuracy of the parameters in the Belin/Ambrósio Enhanced Ectasia Display built in Pentacam, which is designed for the screening of subclinical keratoconus (SKC) built in Pentacam, and the parameters in Corneal visualization Scheimpflug technology (Corvis ST). METHODS: A retrospective study: The fellow eyes of unilateral keratoconus cases were diagnosed with SKC. Patients presented to Shanxi Eye Hospital with SKC from October 2020 to November 2021 were included as the SKC group, and myopic patients undergoing corneal refractive surgery at the Refractive Surgery Department in our hospital within the same period were included as the control group. The Belin/Ambrósio and Corvis ST parameters were extracted from the system and analyzed using independent samples t test. Receiver operating curves (ROCs) were also created to test the diagnostic accuracy of each parameter. RESULTS: There were 70 patients (70 eyes) in the SKC group and 137 patients (137 eyes) in the control group. For Corvis ST parameters, Radius (P = 0.021), PachySlope (P = 0.040), SP-A1 (P = 0.002), A2 Deformation Amp. (P = 0.028), A2 Deflection Length (P < 0.001), Max ICR (P = 0.005), DA Ratio Max (1 mm) (P = 0.023), IR (P = 0.016), CBI (P = 0.003) and TBI (P < 0.001) were statistically different between the two groups. For Belin/Ambrósio parameters, PPI min. Axis, ART min, ART max, ART avg, Pachy min, Front K2, Astig, BAD-Df, BAD-Db, BAD-Dp, BAD-Dt, BAD-Da, BAD-D, PPI min, PPI max, PPI max. Axis, PPI avg and Dist.Apex-Thin.Loc. were significantly different between the two groups (all p < 0.001). TBI and BAD-D showed the best diagnostic accuracy, with AUCs of 0.944 and 0.965, respectively. CONCLUSIONS: Some Belin/Ambrósio and Corvis ST parameters differed between SKC eyes and eyes with normal cornea. TBI and BAD-D showed the ideal diagnostic performance for SKC. In clinical practice, conventional corneal topography could not be replaced by Corvis ST.

Detection ability of corneal biomechanical parameters for early diagnosis of ectasia.

PURPOSE: To assess the detection ability of corneal biomechanical parameters for early diagnosis of ectasia. METHODS: This retrospective descriptive-analytical study included 134 normal eyes (control group) from 134 healthy subjects and 128 eyes with asymmetric contralateral corneal ectasia with normal topography (ACE-NT, study group) from 128 subjects with definite keratoconus in the opposite eye. Placido-disk-based corneal topography with TMS-4, Scheimpflug corneal tomography with Pentacam HR, and corneal biomechanical assessment with Corvis ST and ocular response analyzer (ORA) were performed. A general linear model was used to compare Corvis ST and ORA biomechanical parameters between groups, while central corneal thickness (CCT) and biomechanically corrected intraocular pressure (bIOP) were considered covariates. Receiving operator sensitivity curve (ROC) analysis was used to determine the cut-off point with the highest sensitivity and specificity along with the area under the curve (AUC) for each parameter. RESULT: All parameters of Corvis ST and ORA showed a statistically significant difference between the two groups except for the first (P = 0.865) and second (P = 0.226) applanation lengths, and deformation amplitude (P = 0.936). The discriminative analysis of corneal biomechanical showed that the highest accuracy for the classic, new, and combined parameters of Corvis ST was related to HCR (AUC: 0.766), IR & DAR (0.846), and TBI (0.966), respectively. Using ORA, the corneal resistance factor (0.866) had a higher detection ability than corneal hysteresis (0.826). CONCLUSIONS: TBI has the best accuracy and the highest effect size for differential diagnosis of normal from ACE-NT eyes with a cut-off point of 0.24.

Corneal ectasia detection by epithelial pattern standard deviation from OCT.

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.

Unexpectedly high corneal flap thickness and ectasia after mechanical LASIK / Espessura inesperadamente alta do flap corneano e ectasia após LASIK mecânico

ABSTRACT LASIK is a refractive surgical procedure in which a corneal flap is created to expose the corneal stromal bed. Preoperative estimation of corneal flap thickness is necessary to calculate the percentage tissue altered in LASIK, an important quantitative risk factor for ectasia. The objective of this study was to assess flap thickness and calculate percentage tissue altered to check if unexpectedly thicker flaps and higher percentage tissue altered could pose as risk factors of ectasia. Four subjects (eight eyes) were submitted to mechanical LASIK in 2009 and 2010. Pre and postoperative clinical and tomographic data were reviewed. Mean preoperative estimated percentage tissue altered was 39.18±1.31%, which was borderline for increased ectasia risk when considering the limit of 40%. However, when considering the postoperatively measured flap thickness, the actual mean percentage tissue altered turned out to be 45.17 ± 4.13%, which was significantly higher than predicted preoperatively (p=0.002). Unexpectedly higher postoperative percentage tissue altered may be responsible for corneal ectasia after mechanical LASIK.

RESUMO A LASIK é um procedimento cirúrgico refrativo, no qual um retalho corneano é criado para expor o leito estromal corneano. A estimativa pré-operatória da espessura do retalho corneano é necessária para calcular o percentual de tecido alterado no LASIK, um importante fator de risco quantitativo para ectasia. O objetivo deste estudo foi avaliar a espessura do retalho e calcular o percentual de tecido alterado para verificar se retalhos inesperadamente mais espessos e percentuais de tecido alterado mais altos poderiam representar fatores de risco de ectasia. Quatro indivíduos (oito olhos) foram submetidos à LASIK mecânica em 2009 e 2010. Dados clínicos e tomográficos pré e pós-operatórios foram revisados. A média de percentual de tecido alterado pré-operatória estimada foi de 39,18±1,31%, limítrofe para risco aumentado de ectasia quando considerado o limite de 40%. No entanto, ao considerar a espessura do retalho medida no pós-operatório, o percentual de tecido alterado médio real foi de 45,17±4,13%, ou seja, significativamente maior do que o previsto no pré-operatório (p=0,002). O percentual de tecido alterado pós-operatóriao inesperadamente mais alto pode ser responsável pela ectasia da córnea após LASIK mecânico.

Ectasia Risk Model: A Novel Method Without Cut-off Point Based on Artificial Intelligence Improves Detection of Higher-Risk Eyes.

PURPOSE: To develop a new ectasia risk model through artificial intelligence (AI) and machine learning, enabling the creation of an integrated method without a cut-off point per risk factor, and subsequently better at differentiating patients at higher risk of ectasia with normal topography. METHODS: This comparative case-control study included 339 eyes with normal preoperative topography, with 65 eyes that developed ectasia after laser in situ keratomileusis (ectasia group) and 274 eyes that did not develop ectasia (control group). The AI model used known risk factors to engineer 14 additional ones, totaling 20 features. In this methodology, no variable is used in isolation because its cut-off point is never considered. All separation between cases and controls is made through the interaction detected by the machine learning model that gathers the variables considered relevant. The ability to correctly separate ectatic cases identified as high risk, ectatic cases wrongly classified as low risk, and controls were illustrated by the diagram t-distributed stochastic neighbor embedding (t-SNE). RESULTS: Only two original variables (percent tissue altered and corneal thickness) and two derived from the feature engineering process (derivative percent tissue altered and age weighted value) were selected by the final AI model (ie, best performing AI-based model to separate patients at higher risk). The t-SNE visualization demonstrated the greater ability to differentiate between patients considered at risk by the AI-based model, without a cut-off point, compared to all other methods used alone (P < .0001). CONCLUSIONS: This study describes a new AI-based model that integrates different risk factors without a cut-off point, increasing the number of cases correctly identified as at higher risk. [J Refract Surg. 2022;38(11):716-724.].

Detection of Corneal Ectasia Using OCT Maps of Pachymetry and Posterior Surface Mean Curvature.

PURPOSE: To quantify the abnormal corneal thinning and posterior surface steepening that is observed in keratoconus with an Ectasia Index. METHODS: Optical coherence tomography (OCT) was used to image the corneas of normal individuals and patients with varying stages of keratoconus (manifest, subclinical, and forme fruste). Maps of corneal pachymetry and posterior surface mean curvature were generated, and an Ectasia Index was calculated by multiplying Gaussian fits obtained from the two types of maps. Repeated five-fold cross-validation was used to evaluate the ability of the Ectasia Index to differentiate between normal and keratoconic eyes. The classification performance of the Ectasia Index was compared to minimum pachymetry and maximum posterior mean curvature. RESULTS: Thirty-two eyes from 16 normal individuals, 89 eyes from 63 patients with manifest keratoconus, 16 eyes from 15 patients with subclinical keratoconus, and 26 eyes from 26 patients with forme fruste keratoconus were included in the study. During cross-validation, 100% of the eyes with manifest (89 of 89) and subclinical (16 of 16) keratoconus were correctly classified by the Ectasia Index. The average classification accuracy for the forme fruste keratoconus group was 63 ± 21% (16.4 of 26). The specificity for the normal group was 91 ± 10% (29.1 of 32). The Ectasia Index had a higher sensitivity for keratoconus detection and similar specificity in comparison to minimum pachymetry and maximum posterior mean curvature. CONCLUSIONS: The Ectasia Index could be a valuable additional metric for clinicians to consider when screening for keratoconus. [J Refract Surg. 2022;38(8):502-510.].

Evaluation of Corneal Biomechanical Indices in Distinguishing Between Normal, Very Asymmetric, and Bilateral Keratoconic Eyes.

PURPOSE: To evaluate the ability of biomechanical indices provided by the Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments) and dynamic Scheimpflug analyzer (Corvis ST; Oculus Optikgeräte GmbH) to distinguish between normal eyes and eyes with very asymmetric ectasia (VAE) and mild and moderate keratoconus. METHODS: This prospective, observational, and monocentric study included normal eyes (defined as keratoconus percentage index < 60, Belin/Ambrósio total deviation value [BAD-D] < 1.6, inferior-superior keratometry [I-S value] < 1.45 and maximum keratometry [Kmax] < 47) and eyes with clinical bilateral keratoconus (mild and moderate) and VAE (defined as unilateral keratoconus, where one eye showed a clinical keratoconus and the fellow eye was topographically normal [VAE-NT] or topographically and tomographically normal [VAE-NTT]). All eyes were measured by the Pentacam (Oculus Optikgeräte GmbH), ORA, and Corvis ST. Receiver operating characteristic curve analysis was performed to test the diagnostic ability. RESULTS: Fifty-eight normal eyes and 238 ectatic eyes were included. The highest area under the curve (AUC) was provided by the Corvis Biomechanical Index (CBI) with an AUC of 0.979, followed by ORA corneal resistance factor (0.865), and corneal hysteresis (0.824) separating normal eyes from all ectatic subgroups. The AUC of the CBI was statistically significantly higher than all other parameters (DeLong test, P < .001). A sensitivity of 100% and 70.9%, respectively, and a specificity of 93.1% was found to distinguish normal eyes from VAE-NT and VAE-NTT using a cut-off value of 0.2. CONCLUSIONS: The assessment of biomechanical properties is an additional important method to evaluate corneal ectasia independent of its stage. The CBI provides further information for ectasia screening in cases where corneal topography and tomography are clinically not suspicious by using a cutoff of 0.2. [J Refract Surg. 2022;38(6):364-372.].