Assessment of the specificity of corvis biomechanical index-laser vision correction (CBI-LVC) in stable corneas after phototherapeutic keratectomy.

PURPOSE: The Corvis Biomechanical Index-Laser Vision Correction (CBI-LVC) is a biomechanical index to detect ectasia in post-refractive surgery patients (PRK, LASIK, SMILE). This study aims to evaluate the distribution of the CBI-LVC in stable patients who underwent Phototherapeutic Keratectomy (PTK) compared to PRK patients. METHODS: Patients who underwent PRK and PTK performed between 2000 and 2018 in Humanitas Research Hospital, Rozzano, Milan, Italy and remained stable for at least four years post-surgery were included. All eyes were examined with the Corvis ST (Oculus, Germany), whose output allows the calculation of the CBI-LVC. The distribution and specificity of the CBI-LVC in the two populations were estimated using a Wilcoxon Mann-Whitney test and compared. RESULTS: 175 eyes of 148 patients were included (85 eyes of 50 PTK patients and 90 eyes of 90 PRK patients). The distribution of CBI-LVC in the two groups showed a minor difference, with a median value in PRK patients of 0.000 (95% CI 0.000; 0.002) and 0.008 (95% CI 0.000; 0.037) in PTK patients (Mann-Whitney U test p = 0.023). The statistical analysis showed that the CBI-LVC provided a specificity of 92.22% in the PRK group, while in the PTK group it was 82.35%. Nevertheless, this difference was not statistically significant (Chi-squared test with Yates, p = 0.080). CONCLUSION: CBI-LVC provided similar specificity in stable PTK patients compared to those who underwent PRK. These results suggest that the CBI-LVC could be a useful tool to aid corneal surgeons in managing PTK patients.

Ectatic diseases.

Ectatic corneal disease (ECD) comprises a group of disorders characterized by progressive thinning and subsequent bulging of the corneal structure. Different phenotypes have been recognized, including keratoglobus, pellucid marginal degeneration (PMD), and keratoconus (KC). Keratoconus has been widely investigated throughout the years, but the advent of laser refractive surgery boosted an immediate need for more knowledge and research about ectatic diseases. This article discusses nomenclature of ectatic disease, etiology and pathogenesis, along with treatment options, with special focus ok KC and forme fruste keratoconus.

Effect of Corneal Tilt on the Determination of Asphericity.

Purpose: To quantify the effect of levelling the corneal surface around the optical axis on the calculated values of corneal asphericity when conic and biconic models are used to fit the anterior corneal surface. Methods: This cross-sectional study starts with a mathematical simulation proving the concept of the effect that the eye's tilt has on the corneal asphericity calculation. Spherical, conic and biconic models are considered and compared. Further, corneal asphericity is analysed in the eyes of 177 healthy participants aged 35.4 ± 15.2. The optical axis was determined using an optimization procedure via the Levenberg-Marquardt nonlinear least-squares algorithm, before fitting the corneal surface to spherical, conic and biconic models. The influence of pupil size (aperture radii of 1.5, 3.0, 4.0 and 5.0 mm) on corneal radius and asphericity was also analysed. Results: In computer simulations, eye tilt caused an increase in the apical radii of the surface with the increase of the tilt angle in both positive and negative directions and aperture radii in all models. Fitting the cornea to spherical models did not show a significant difference between the raw-measured corneal surfaces and the levelled surfaces for right and left eyes. When the conic models were fitted to the cornea, changes in the radii of the cornea among the raw-measured corneal surfaces' data and levelled data were not significant; however, significant differences were recorded in the asphericity of the anterior surfaces at radii of aperture 1.5 mm (p < 0.01). With the biconic model, the posterior surfaces recorded significant asphericity differences at aperture radii of 1.5 mm, 3 mm, 4 mm and 5 mm (p = 0.01, p < 0.01, p < 0.01 & p < 0.01, respectively) in the nasal temporal direction of right eyes and left eyes (p < 0.01, p < 0.01, p < 0.01 & p < 0.01, respectively). In the superior-inferior direction, significant changes were only noticed at aperture radii of 1.5 mm for both right and left eyes (p = 0.05, p < 0.01). Conclusions: Estimation of human corneal asphericity from topography or tomography data using conic and biconic models of corneas are affected by eyes' natural tilt. In contrast, the apical radii of the cornea are less affected. Using corneal asphericity in certain applications such as fitting contact lenses, corneal implant design, planning for refractive surgery and mathematical modelling when a geometrical centre of the eye is needed should be implemented with caution.

Correction to: Visual, refractive and topographic outcomes of progressive thickness intrastromal corneal ring segments for keratoconic eyes.

In the original publication, the Results paragraph of the abstract was published incorrectly. The correct version should read as follows.

Visual, refractive and topographic outcomes of progressive thickness intrastromal corneal ring segments for keratoconic eyes.

PURPOSE: To evaluate one-year visual, refractive, and topographic outcomes of 58 eyes of 53 keratoconus patients who underwent surgery with a progressive thickness intrastromal corneal ring segment (ICRS). METHODS: This multi-center, retrospective, observational study evaluates the one-year effects of progressive thickness ICRS implanted in keratoconus patients meeting the inclusion criteria. One or two progressive ICRS were implanted in the selected eyes after creating an intrastromal tunnel with a femtosecond laser. Pre- and postoperative uncorrected distance visual acuity, best-corrected distance visual acuity, manifest refraction (both spherical equivalent and cylindrical refractions), corneal astigmatism, maximum keratometry, corneal thickness, and corneal topography measurements and indices were evaluated. RESULTS: In this retrospective case series, 58 eyes of 53 keratoconus patients were included with a follow-up of 12 months. The mean age was 30.89 ± 11.90 years. There were improvements postoperatively in mean values of visual acuities, both uncorrected from 0.71 (preoperatively) to 0.28 (log MAR), and best-corrected from 0.28 to 0.10 (log MAR), mean cylindrical refraction from - 2.35 ± 1.51 to - 4.15 ± 2.23 D, and mean spherical equivalent from - 2.10 ± 2.25 to - 4.64 ± 3.2 D. There was also a reduction in maximal keratometry from 54.21 D preoperatively to 50.93 D postoperatively. CONCLUSION: The implantation of the progressive thickness ICRS is an effective and safe method to improve the vision of keratoconic eyes. Corneal stability was maintained at the 12-month mark.

Ex-vivo experimental validation of biomechanically-corrected intraocular pressure measurements on human eyes using the CorVis ST.

The purpose of this study was to assess the validity of the Corvis ST (Oculus; Wetzlar, Germany) biomechanical correction algorithm (bIOP) in determining intraocular pressure (IOP) using experiments on ex-vivo human eyes. Five ex-vivo human ocular globes (age 69 ±â€¯3 years) were obtained and tested within 3-5 days post mortem. Using a custom-built inflation rig, the internal pressure of the eyes was controlled mechanically and measured using the CorVis ST (CVS-IOP). The CVS-IOP measurements were then corrected to produce bIOP, which was developed for being less affected by variations in corneal biomechanical parameters, including tissue thickness and material properties. True IOP (IOPt) was defined as the pressure inside of the globe as monitored using a fixed pressure transducer. Statistical analyses were performed to assess the accuracy of both CVS-IOP and bIOP, and their correlation with corneal thickness. While no significant differences were found between bIOP and IOPt (0.3 ±â€¯1.6 mmHg, P = 0.989) using ANOVA and Bonferroni Post-Hoc test, the differences between CVS-IOP and IOPt were significant (7.5 ±â€¯3.2 mmHg, P < 0.001). Similarly, bIOP exhibited no significant correlation with central corneal thickness (p = 0.756), whereas CVS-IOP was significantly correlated with the thickness (p < 0.001). The bIOP correction has been successful in providing close estimates of true IOP in ex-vivo tests conducted on human donor eye globes, and in reducing association with the cornea's thickness.

Correlation between different Scheimpflug-based lens densitometry analysis and effective phacoemulsification time in mild nuclear cataracts.

PURPOSE: To assess the correlations between preoperative Scheimpflug-based lens densitometry and effective phacoemulsification time (EPT) in age-related nuclear cataracts. DESIGN: Retrospective consecutive study. METHODS: The setting was the Ophthalmology Department, Hospital de Braga, Portugal. The study population included 50 eyes (42 patients) with age-related nuclear cataracts submitted to uneventful phacoemulsification surgery. Different analysis methods of Scheimpflug-based lens densitometry were performed: Pentacam Nucleus Staging (PNS) score with an ordinal scale from 0 to 5 and three-dimensional (3D), linear and region of interest (ROI) methods, which are displayed on an absolute scale (from 0 to 100%). EPT was calculated for the cataract surgery, which was performed by the same surgeon. Correlations between lens densitometry variables and EPT were determined using Pearson or Spearman correlation coefficients according to data normality. RESULTS: There were significant correlations between EPT and average density and maximum density variables derived from the 3D (r = 0.596, p < 0.001; r = 0.632, p < 0.001, respectively) and ROI (r = 0.527, p < 0.001; r = 0.575, p < 0.001, respectively) methods. The average density was the only parameter derived from the linear analysis that showed a significant correlation with EPT (r = 0.293, p = 0.039). The PNS score did not show a significant correlation with EPT (rho = 0.124, p = 0.390). CONCLUSION: The densitometric parameters based on the 3D method showed the highest correlations with EPT. The referred lens densitometric analysis approach may be used in preoperative assessment in order to predict EPT more efficiently in age-related nuclear cataracts.

Role of the corneal epithelium measurements in keratorefractive surgery.

PURPOSE OF REVIEW: Refractive surgery has stimulated considerable progress in corneal and anterior segment imaging, and optical characterization of the eye. From front surface corneal topography, we evolved to three-dimensional corneal tomography with limbus to limbus characterization of the front and back corneal surfaces and pachymetric mapping. Corneal anatomical evaluation has further evolved to layered or segmental tomography with the ability to characterize corneal epithelial thickness profile and the elevation of stromal front surface. Further characterization of even more specific structures, such as Bowman's layer and Descement's membrane, has been also demonstrated. The applications of such understanding in keratorefractive surgery are reviewed. RECENT FINDINGS: Understanding the corneal epithelial profile is of interest in many areas of ophthalmology, especially in refractive surgery. The most relevant applications include screening candidates at higher risk for complications (i.e. progressive ectasia and tear dysfunction syndrome), planning primary procedures, enhancements, and therapeutic surgery, and also postoperatively understanding the wound healing and clinical outcomes. SUMMARY: Corneal epithelial thickness was first available using digital very-high-frequency ultrasound. Advances in anterior segment optical coherence tomography enabled such fundamental evaluation, which accelerated progress. Such knowledge significantly impacts safety and efficacy of refractive surgery, and also allows for significant improvement for therapeutic procedures. VIDEO ABSTRACT.

Discriminant value of custom ocular response analyzer waveform derivatives in keratoconus.

PURPOSE: To evaluate the performance of corneal hysteresis (CH), corneal resistance factor, and 16 investigator-derived Ocular Response Analyzer (ORA) variables in distinguishing keratoconus (KC) from the nondiseased state. DESIGN: Retrospective case series. PARTICIPANTS: Fifty-four eyes of 27 unaffected patients and 49 eyes of 25 KC patients from the Instituto de Olhos, Rio de Janeiro, Brazil. METHODS: Sixteen candidate variables were derived from exported ORA signals to characterize putative indicators of biomechanical behavior. Area under the receiver operating characteristic curve (AUC) and the Z statistic were used to compare diagnostic performance. MAIN OUTCOME MEASURES: Discriminant value of standard and derived ORA variables as measured by AUC. RESULTS: Fifteen of 16 candidate variables performed significantly better than chance (AUC, >0.5) at discriminating KC. Diagnostic performance was greatest for a custom variable related to the depth of deformation as defined by the minimum applanation signal intensity during corneal deformation (concavity(min); mean AUC ± standard error, 0.985 ± 0.002) and a new measure incorporating the pressure-deformation relationship of the entire response cycle (hysteresis loop area, 0.967 ± 0.002). Z statistics assessing the discriminative value of each of the top 5 variables demonstrated superiority to CH (AUC, 0.862 ± 0.002). Concavity(min) had the best overall predictive accuracy (cutoff value, 50.37; 94.9% sensitivity, 91.7% specificity, and 93.2% test accuracy), and the top 4 variables demonstrated the most consistent relationships to KC severity. CONCLUSIONS: Investigator-derived ORA variables related to the depth of deformation and the pressure-deformation relationship demonstrated very high test accuracy for detecting the presence of KC. Beyond their diagnostic value, the candidate variables described in this report provide mechanistic insight into the nature of the ORA signal and the characteristic changes in corneal dynamics associated with KC.

Ocular biomechanical metrics by CorVis ST in healthy Brazilian patients.

PURPOSE: To evaluate ocular biomechanical metrics given by the CorVis ST (Oculus, Inc., Berlin, Germany) in a population of healthy Brazilian patients. METHODS: An observational and cross-sectional study involving 1 eye randomly selected from 90 healthy patients. Studied parameters (including deformation amplitude, first applanation time, highest concavity time, second applanation time, first applanation length, second applanation length, curvature radius highest concavity, curvature radius normal, velocity in, and velocity out) derived from the CorVis ST were correlated to central corneal thickness from the Pentacam (Oculus, Inc.). Differences between data on the basis of gender were evaluated. RESULTS: Mean patient age was 35.80 ± 12.83 years (range: 21.07 to 78.84 years). Mean central corneal thickness was 547.50 ± 32.00 µm (range: 490 to 647 µm) and mean spherical equivalent refraction was -3.29 ± 3.69 diopters (range: -9.50 to +10.37 diopters). Mean deformation amplitude was 1.05 ± 0.08 mm (range: 0.91 to 1.26 mm). Highest concavity time was 18.38 ± 0.93 ms (range: 16.95 to 21.07 ms). Intraocular pressure was 16.43 ± 2.15 mm Hg (range: 11.50 to 21.0 mm Hg). First applanation time was 8.32 ± 0.33 ms (range: 7.53 to 9.12 ms) and second applanation time was 23.80 ± 0.44 ms (range: 22.76 to 24.95 ms). First applanation length (max) was 2.07 ± 0.38 mm (range: 1.20 to 3.10 mm) and second applanation length (max) was 2.37 ± 0.47 mm (range: 1.33 to 4.12 mm). Curvature radius highest concavity was 11.09 ± 2.06 mm (range: 7.58 to 15.98 mm) and curvature radius normal was 7.59 ± 0.67 mm (range: 6.82 to 11.02 mm). Velocity in was 0.21 ± 0.05 m/s (range: 0.16 to 0.72 m/s) and velocity out was -0.33 ± 0.07 m/s (range: -0.72 to -0.20 m/s). Studied parameters were not associated with gender. CONCLUSIONS: Eight of 11 ocular biomechanical metrics given by the CorVis ST were associated with central corneal thickness, but the influence of central corneal thickness on these measurements was low.

Optical coherence tomography combined with videokeratography to differentiate mild keratoconus subtypes.

PURPOSE: To develop parameters using a combination of optical coherence tomography (OCT) and videokeratography to detect early keratoconus. METHODS: Videokeratography, wavefront analysis, and measured OCT indices were performed on 180 normal eyes, 46 eyes with moderate keratoconus, 54 eyes with early keratoconus, 7 eyes with forme fruste keratoconus, and 16 eyes with keratoconus "suspect" to determine the most sensitive parameters for separating these groups. RESULTS: A combination of videokeratography and OCT indices (inferior-superior [I-S] value and minimum pachymetry) was statistically the most significant in separating the keratoconus groups from normal eyes (P < .001). Using a newly derived index, the minimum pachymetry divided by the I-S value (pachymetry/asymmetry [PA]/I-S index) with a cut-off of 100, 100% of early and forme fruste keratoconus could be identified as being abnormal with 7 normals misclassified (misclassification rate 2.7%). By adding keratoconus "suspect" to the analysis and an I-S value of 1.2 as a cut-off point, 5 "suspects" were classified as normal and 11 normals as abnormal (misclassification rate 7.8%). The PA/I-S index, with a cut-off point of 100, reduced this misclassification rate to 4.4%. CONCLUSIONS: These results suggest that OCT combined with videokeratography may be more useful for differentiating mild forms of keratoconus than videokeratography alone.

Tomographic parameters for the detection of keratoconus: suggestions for screening and treatment parameters.

Tomographic corneal evaluation has added significantly more information in the evaluation of the ectatic cornea. Additional information from the posterior cornea and a full corneal thickness map in addition to anterior corneal analysis has increased the ability to identify early and subtle corneal changes. Although these newer examination modalities have increased our sensitivity in refractive screening, problems still persist when attempting to assure treatment trials (such as collagen cross-linking) for early disease are performed to an appropriate patient population. This article will review past and present diagnostic capabilities with a particular emphasis on refractive screening and early treatment studies and stress the limitations of our current diagnostic ability when it comes to diagnosing early ectatic change.

Evaluation of the effect of artificial tears on corneal epithelial thickness changes after photorefractive keratectomy.

PURPOSE: This study aimed to evaluate the corneal epithelial thickness changes after photorefractive keratectomy (PRK) and the impact of long-term artificial tear usage on epithelial thickness changes in these patients. METHODS: This study was performed on 71 patients (142 eyes) without dry eye disease who received PRK for myopic refractive correction. The corneal epithelial thickness profile was obtained before, one, three, and six months after surgery using anterior segment optical coherence tomography. Patients were randomly divided into two groups: group A, who received preservative-free artificial tears post-surgery, and group B, who did not receive artificial tears. RESULTS: The epithelial thickness decreased universally in the first month and then increased in the 3- and 6-month follow-ups. Group A had a significantly thicker epithelium in central, paracentral, and midperipheral zones compared with group B in the 3-month follow-up. In the 6-month follow-up, no significant differences were detected between groups. At the last follow-up, the central, paracentral, and midperipheral zone epithelial thicknesses in all patients were significantly higher than preoperative values, but peripheral zone thickness only increased to preoperative values. CONCLUSIONS: Patients using artificial tears showed a faster thickening, especially in the central and paracentral zones, but there were no significant differences between the two groups in the final follow-up. Artificial tear usage may increase the rate of the epithelial remodeling process in post-PRK patients without significantly altering the final epithelial thickness profile. Further studies are warranted to evaluate the influence of different factors on epithelial remodeling.

Myopia Prevalence in Latin American Children and Adolescents: A Systematic Review and Meta-Analysis.

Although myopia is a growing global concern, comprehensive studies on its prevalence among Latin American (LATAM) children and adolescents are still lacking. Thus, we conducted a systematic review and meta-analysis to determine the prevalence of myopia in LATAM children and adolescents aged three to 20. The study conducted a thorough literature search from January 1, 1975, to February 28, 2023, identifying 24 studies on the prevalence of myopia in LATAM that met the inclusion criteria. Quality assessment and standardized data collection were performed. The meta-analysis used a random-effects model due to heterogeneity and calculated prevalence rates. Finally, the analysis of data from 24 eligible studies revealed a myopia prevalence of 8.61% (range 0.80-47.36%, 95% confidence interval (CI): 5.22-13.87%, p < 0.05) among 165,721 LATAM children and adolescents. No significant age-based associations or temporal trends were observed in this study. Studies with non-cycloplegic or objective assessment exhibited a numerically higher, although statistically non-significant, myopia prevalence (10.62%, 95% CI: 4.9-21.6%) compared to studies using cycloplegia (7.17%, 95% CI: 3.40-14.50%). In conclusion, myopia affects approximately one in 11 LATAM children and adolescents. Given the increasing exposure of LATAM youth to known myopia risk factors, such as extensive near-work, online learning, and limited outdoor activities, it is crucial to monitor myopia trends in this region. Further research is imperative to address and prevent myopia in LATAM.

Advanced Surface Ablation in a Patient With Suspect Topography: A Case Report.

The purpose of this clinical report is to describe a 10-year clinical outcome of advanced surface ablation with photorefractive keratectomy (PRK) in a patient who had been previously incorrectly diagnosed with keratoconus (KC). Corneal ectasia is a rare but extremely relevant complication of laser vision correction, and KC represents a major contraindication for these procedures. Nonetheless, some surface ablation procedures, such as PRK, might be a valid option for particular patients with atypical corneal topography or subclinical or mild forms of KC. Patient education and complete preoperative refractive multimodal imaging are essential for a more conscious therapeutic decision, minimizing iatrogenic ectasia, as well as decreasing the number of patients who are incorrectly denied refractive surgery, as was the patient presented in this study.

Keratoconus and Corneal Ectasia with Relatively Low Keratometry.

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.

Investigation of How Corneal Densitometry Artefacts Affect the Imaging of Normal and Keratoconic Corneas.

PURPOSE: To investigate corneal densitometry artefacts found in Pentacam Scheimpflug scans and their potential effect on assessing keratoconic (KC) corneas compared to normal (N) corneas. METHODS: The current study utilises Pentacam data of 458 N eyes, aged 35.6 ± 15.8 (range 10-87), referred to as the "N group", and 314 KC eyes, aged 31.6 ± 10.8 (range 10-72), referred to as the "KC group", where densitometry data were extracted and analysed via a custom-built MATLAB code. Radial summations of the densitometry were calculated at diameters ranging from 0.5 mm to 5.0 mm. The minimum normalised radial summation of densitometry (NRSD) value and angle were determined at each diameter and then linked. KC cone locations and areas of pathology were determined, and a comparison between N and KC groups was carried out both within the averaged area of pathology and over the corneal surface. RESULTS: Joining minimum NRSD trajectory points marked a clear distortion line pointing to the nasal-superior direction at 65° from the nasal meridian. The findings were found to be independent of eye laterality or ocular condition. Consistency was detected in the right and left eyes among both the N and KC groups. The location of the KC cone centre and the area of pathology were determined, and the densitometry output was compared both within the area of pathology and over the whole cornea. When the average densitometry was compared between N and KC eyes within the KC area of pathology, the N group recorded a 16.37 ± 3.15 normalised grey-scale unit (NGSU), and the KC group recorded 17.74 ± 3.4 NGSU (p = 0.0001). However, when the whole cornea was considered, the N group recorded 16.71 ± 5.5 NGSU, and the KC group recorded 15.72 ± 3.98 NGSU (p = 0.0467). A weak correlation was found between the Bad D index and NGSU when the whole measured cornea was considered (R = -0.01); however, a better correlation was recorded within the KC area of pathology (R = 0.21). CONCLUSIONS: Nasal-superior artefacts are observed in the densitometry Pentacam maps, and analysis shows no significant differences in their appearance between N or KC corneas. When analysing KC corneas, it was found that the cone positions are mostly on the temporal-inferior side of the cornea, opposite to the densitometry artefact NRSD trajectory. The analysis suggests that the corneal densitometry artefacts do not interfere with the KC area of pathology as it reaches its extreme in the opposite direction; therefore, weighting the densitometry map to increase the contribution of the inferior-temporal cornea and decreasing that of the superior-nasal area would improve the classification or identification of KC if densitometry is to be used as a KC metric.

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

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