Posterior Corneal Surface Research Articles

The Influence that the Complexity of the Three-Dimensional Eye Model Used to Generate Simulated Eye-tracking Data Has on the Gaze Estimation Errors Achieved Using the Data

Simulated eye-tracking data are an integral tool in the development of eye-tracking methods. Most of the simulated data used in eye-tracking-related research has been generated using low-complexity eye models that include a single spherical corneal surface. This study investigated the influence of eye-model complexity on the ability of simulated eye-tracking data to predict real-world outcomes. The experimental procedures of two pertinent comparative eye-tracking studies were replicated in a simulated environment using various eye-model complexities. The simulated outcomes were then evaluated against the findings of the comparative studies that were derived from real-world outcomes. The simulated outcomes of both comparative studies were significantly influenced by the eye-model complexity. Eye models that included an aspheric corneal surface best replicated experimental eye-tracking outcomes, while including a posterior corneal surface did not improve the ability of simulated data to replicate real-world outcomes. Using a wide-angle eye model that accurately replicates the peripheral optics of the eye did not improve simulated outcomes relative to a paraxial eye model.

Case Report: Front surface eccentricity of scleral lens: Its impact on visual quality in eyes with higher-order aberrations induced by refractive surgery

Purpose To report the impact of front surface eccentricity (FSE) of scleral lenses (SCLs) on the visual performance of eyes exhibiting refractive surgery-induced higher-order aberrations (HOAs) Method A female teenager presented to the clinic with blurring of vision and dependency on spectacles even after undergoing Small Incision Lenticule Extraction (SMILE) in both eyes (BE). Her presenting uncorrected high contrast distance visual acuity (HCDVA) was 20/60 in the right eye (RE) and 20/40 in the left eye (LE). On examination, the cornea showed a ring-shaped area of ablation with faint scarring and a well-apposed lenticule-extraction site. Subjective refraction improved the HCDVA to 20/20p in RE and 20/25 in LE but the patient was not happy with the quality of vision. Ocular aberrometry revealed an increase in total HOAs as the underlying cause of unsatisfactory vision. Result A contact lens trial was recommended for BE to enhance visual quality. Rigid corneal lenses (RCLs) were tried, but the patient was intolerant to them. Large diameter SCLs of different FSEs (0, 0.6, and 0.8) were tried to reduce these aberrations. SCL with FSE 0 yielded the most favourable visual outcome, which was confirmed subjectively on ocular aberrometry. Conclusion With this case report, we hypothesize that the eccentricity of SCL can be selected according to the asphericity (at 6 mm) of the posterior corneal surface. This case also re-emphasizes the impact of SCL with varying FSEs on reducing HOAs and enhancing visual quality in eyes where conventional RCLs yield suboptimal results.

Changes in corneal curvature and astigmatism in senile cataract patients after phacoemulsification.

Analysis of changes in corneal curvature and astigmatism after phacoemulsification for senile cataracts. Retrospective collection of clinical data from patients who underwent uncomplicated phacoemulsification at the First Affiliated Hospital of Soochow University. The changes in total corneal curvature, anterior surface curvature, posterior surface curvature, and astigmatism were measured by the Sirius system. The axial length was measured by Lenstar 900. The total corneal curvature and anterior surface curvature at 3 months were all larger than those before phacoemulsification, and the difference was statistically significant (p < 0.05). Compared with preoperative results, there was no significant change in corneal posterior surface curvature and astigmatism 3 months after surgery (p > 0.05). Changes in corneal curvature and astigmatism were not significantly correlated with age at 3 months after surgery (p > 0.05). Postoperative astigmatism was increased with the growth of axial length, while corneal curvature was decreased (p < 0.05). Phacoemulsification can lead to increased postoperative corneal curvature in elderly cataract patients, and with the growth of the axial length, the corneal astigmatism was increased.

Pathogenesis of Fuchs endothelial corneal dystrophy, the fibrillar layer and individualized treatment

Fuchs endothelial corneal dystrophy (FECD) is agenetic and age-associated corneal disease characterized by an accelerated loss of corneal endothelial cells and an increased subendothelial deposition of extracellular matrix (ECM). Clinically, advanced disease leads to corneal edema with subsequent reduction in visual acuity. In the majority of patients with advanced FECD, afibrillar layer (FL) appears on the posterior corneal surface. This FL is mostly localized in the inferotemporal corneal quadrant, marks areas with significantly reduced endothelial cell density and increased corneal thickness in the sense of edema and can be visualized and measured using Scheimpflug backscatter analysis due to increased backscatter. FECD is currently the most common indication for corneal transplantation worldwide, usually in the form of Descemet membrane endothelial keratoplasty (DMEK). New treatment approaches include variations of DMEK surgery such as hemi- or quarter DMEK with individualized and smaller grafts or Descemet membrane stripping only (DSO). In the future, clinical imaging of the FL as aparticularly affected endothelial area could be important for FECD progression assessment and planning of surgical interventions. This article provides an overview of the current state of research on the clinical aspects, pathogenesis, fibrillar layer and individualized treatment of FECD.

Corneal changes after large (9mm) lateral rectus muscle recession measured with Pentacam®

ABSTRACT Introduction: The aim of this study was to evaluate alterations in corneal astigmatism, axial anterior corneal curvature, anterior chamber depth, and central corneal thickness (CCT) two months after the unilateral recession of lateral rectus muscle in children. Methods: This prospective study included 37 children with intermittent exotropia who would undergo unilateral lateral rectus muscle recession. All measurements were performed using Pentacam®. Comparisons were made between the operated and fellow unoperated eyes, pre- and post-operatively. The assessment was made for changes in the radius of axial curvature on major meridians at 3 and 3.5 mm from the optical corneal center in the mid-peripheral zone. Astigmatism changes of the anterior and posterior corneal surface were calculated using vector analysis software (astigMATIC®). The interaction between age or CCT and postoperative changes in anterior and posterior surface corneal astigmatism were examined with ANOVA model. Results: In the intervention group, changes in anterior and posterior corneal surface astigmatism were statistically significant, with a mean increase of 0.56Dx90 and 0.08Dx87, respectively. In the mid-peripheral corneal zone, an increase was observed in the radius of anterior corneal axial curvature, more evident temporal 3 and 3.5 mm from the corneal center on the horizontal meridian, with corresponding decrease superiorly and inferiorly at 3 and 3.5 mm from the corneal center on the vertical meridian. Discussion: The changes in total astigmatism of the operated eyes are mainly attributed to the anterior corneal surface. These changes are associated with flattening in the 180 meridian of the cornea, leading to a shift to “with-the-rule” astigmatism.

Longitudinal assessment of the progression of severe keratoconus based on corneal topography

We aimed to assess long-term disease progression in patients with severe keratoconus (KC). Clinical records of 125 patients (201 eyes) with severe KC followed-up for > 12 months were retrospectively analyzed. From these, 28 patients (31 eyes) were included. Corneal topography parameters evaluated included thinnest corneal thickness (TCT), maximum keratometry (Kmax), anterior and posterior mean corneal radii of 3 mm (aKM, pKM), steep keratometry, and KC screening indices. All patients wore rigid gas permeable contact lenses (RGPCLs) for an extended period. The median patient age and follow-up period were 20 (interquartile range [IQR] 17–22) years and 25 (15–38) months, respectively. Compared to baseline, the aKM, Kmax, and KC screening indices on the anterior corneal surface were reduced at the final follow-up (P < 0.05). No changes were observed in RGP-corrected visual acuity, TCT, pKM, or KC screening indices on the posterior corneal surface. The higher the baseline value, the greater the reduction in aKM and Kmax. Five patients (16%) experienced disease progression during follow-up. Patients with severe KC showed reduced anterior corneal surface curvature and no change in corneal thickness during an average follow-up period of 2–3 years while wearing RGPCLs.

Diagnostic ability of the corneal anterior and posterior surface area calculated by corneal modelling approach in early stage keratoconus patients.

To investigate the discrimination ability of the corneal anterior and posterior surface area between patients with keratoconus stage 1 and normal individuals. In this retrospective study, 116 eyes of 116 normal individuals and 366 eyes of 366 keratoconus patients were included. Keratoconus patients were divided into six groups according to the topographic keratoconus classification of Pentacam. Anterior and posterior surface data of sagittal (SM) and elevation maps (EM) were exported from Pentacam, and human corneal models were created employing the software utilizing the PyVista module of Python programming language. The anterior and posterior corneal surface area (a-CSA and p-CSA) of SM and EM were calculated by the software ranging from central 3 to 8mm diameter. Anterior and posterior CSA values were higher in KC patients compared to normal individuals (p < 0.001). The p-CSA for SM and EM measured at the central 3mm was higher in patients with KC-1 compared to normal eyes (p = 0.002, p = 0.005, respectively), For both maps, a-CSA and p-CSA measured at the central 4 and 5mm were higher in KC-1 compared to normal individuals (p < 0.05). The highest area under the curve (AUC) values in the diagnosis patients with KC-1 were obtained from 3mm p-CSA for SM (AUC: 0.8338), 3mm p-CSA for EM (AUC: 0.7999), 4mm p-CSA for SM (AUC: 0.8531), 4mm p-CSA for EM (AUC:0.7948), 5mm p-CSA for SM (AUC: 0.8455), 5mm p-CSA for EM (AUC:0.7614). The corneal surface area as a parameter, especially for central 3, 4, and 5mm, has a discrimination ability in diagnosing keratoconus disease and distinguishes normal eyes from KC-1 eyes.

Posterior corneal surface stability after femtosecond laser-assisted in situ keratomileusis in patients with myopia and myopic astigmatism.

To evaluate the variation and stability of the posterior cornea surface parameters (posterior cornea curvature [PCC], posterior cornea astigmatism [PCA], and posterior cornea elevation [PCE]) after femtosecond laser-assisted in situ keratomileusis (LASIK) in patients with myopia and myopic astigmatism over a period of 6 months or longer. This retrospective study comprised 284 right eyes. Patients aged 18 years or older with myopia up to -12.00 D and/or astigmatism up to -6.00 DC and who underwent femtosecond LASIK were recruited. Patients were divided into three subgroups: low myopia (-0.50 to -3.00 D), moderate myopia (>-3.00 to ≤-6.00 D), and high myopia (>-6.00 D), according to their pre-LASIK spherical equivalent (SE). The variables included for analysis were PCC (central 0-3.0 mm, pericentral 3.0-6.0 mm, and peripheral region 6.0-9.0 mm), PCE, PCA, internal anterior chamber depth, intraocular pressure, and central cornea thickness at the pre- and post-LASIK stages. The central PCC remained unchanged across all three myopia subgroups at 1 month when compared to the pre-LASIK stage and remained stable at 6 months. The pericentral regions became flatter across all myopia subgroups at 1 month postsurgery (P < 0.001) and remained unchanged at 6 months. This trend was not seen in the peripheral cornea regions, which remained unchanged at 1 and 6 months post-LASIK when compared to pre-LASIK mean readings. There were minimal changes in post-LASIK posterior cornea astigmatism throughout follow-up. There was no incidence of post-LASIK surgery ectasia in this study population. Post-LASIK, the different cornea subregions behaved differently. Overall, the posterior cornea surface remained stable post-LASIK across all myopia subgroups throughout follow-up.

Posterior corneal stability after small incision lenticule extraction with different optical zones.

To assess the changes in the posterior corneal surface following small incision lenticule extraction (SMILE) with different optical zones. In this retrospective study, 106 eyes of 106 patients who underwent SMILE were recruited 3 years after the procedure. Eyes were divided into two groups according to the size of the surgical optical zone: group A (52 eyes, ≤6.2 mm) and group B (54 eyes, ≥6.5 mm). Posterior central elevation (PCE) and 12 other points at 45°, 135°, 225° and 315° with distances of 1 mm, 2 mm and 3 mm from the centre were recorded from Pentacam. No iatrogenic keratectasia was identified, and eyes in the two groups showed comparable visual results. The overall trend in posterior corneal elevation changes was consistent for both groups. PCE decreased significantly from 1.33 ± 2.32 to 0.75 ± 2.41 in group A (P = 0.024) and from 0.87 ± 2.61 to 0.06 ± 2.74 in group B (P = 0.003). All points in the central 2 mm region in both groups were reduced postoperatively. In the 4 mm and 6 mm corneal annulus, almost all points at 225°and 315° showed backward displacement, with the most prominent change occurring at 315° in the 6 mm annulus (P < 0.001), indicating no forward protrusion in the inferior area. No forward protrusion in the posterior corneal surface was observed 3 years after SMILE with different optical zones. Comprehensive preoperative measurements are essential for ensuring corneal stability and avoiding iatrogenic keratectasia.

Evaluation of Different Corneal Powers Measured by Corneal Tomography in Intraocular Lens Power Calculation

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

Investigation of the optimal cutting depth in small incision lenticule extraction based on a collagen fibril crimping constitutive model of the cornea

To investigate the optimal cutting depth (Cap) in small incision lenticule extraction from the perspective of corneal biomechanics, a three-dimensional finite element model of the cornea was established using a stromal sub-regional material model to simulate small incision lenticule extraction. The displacement difference PΔ at the central point of the posterior corneal surface before and after lenticule extraction, as well as the von Mises stress at four points of different thicknesses in the center of the cornea, were analyzed using the finite element model considering the hyperelastic property and the difference in stiffness between the anterior and posterior of the cornea. The numerical curves of PΔ-Cap and von Mises Stress-Cap relations at different diopters show that the displacement difference PΔ has a smallest value at the same diopter. In this case, the von Mises stress at four points with different thicknesses in the center of the cornea was also minimal. Which means that the optimal cutting depth exsisting in the cornea. Moreover, PΔ-Cap curves for different depth of stromal stiffness boundaries show that the optimal cap thickness would change with the depth of the stromal stiffness boundary. These results are of guiding significance for accurately formulating small incision lenticule extraction surgery plans and contribute to the advancement of research on the biomechanical properties of the cornea.

Importance of Higher-Order Aberrations on Both Anterior and Posterior Surfaces After Pterygium Surgery.

The purpose of this study was to investigate the changes in higher-order aberrations (HOAs), coma, and spherical aberrations (SAs) on the anterior, posterior, and total corneal surfaces after pterygium excision. In this single-center study, we examined 19 eyes of 15 patients who underwent pterygium excision at Yokohama Minami Kyosai Hospital between January 2017 and December 2017. We also evaluated 25 eyes of 25 age-matched patients with no history of ocular disease as the control group. Corneal topography, total HOAs, coma, and SAs in all regions at 4 and 6 mm diameters were evaluated using anterior segment optical coherence tomography (CASIA SS-1000, Tomey, Japan). The pterygium area and extent were also assessed. Significant improvements in the HOAs, coma, and SAs at both diameters were observed in the total and anterior corneas from the first postoperative month. Notably, the posterior cornea showed significant improvements in HOAs (4 mm: P < 0.001 [log HOAs]; 6 mm: P = 0.001 [log HOAs]) and coma (4 mm: P = 0.003 [log coma], 6 mm: P = 0.002 [log coma]) within both diameters at 1 month postoperatively. A strong correlation was identified among the pterygium area, posterior HOAs, and coma (Spearman correlation = 0.651). Pterygium induced 2 D of astigmatism when extension exceeded 2.1 mm. HOAs in both the anterior and posterior corneas improved after pterygium excision. This finding underscores the importance of considering corneal aberrations on both anterior and posterior surfaces in pterygium management.

Higher order aberrations in keratoconus‏.

Keratoconus is a progressive disorder of the cornea that causes thinning (Sedaghat et al. in Sci Rep 11(1):11971, 2021), ectasia, and irregular astigmatism, resulting in poor visual acuity that cannot be corrected with standard sphero-cylindrical spectacle lenses. One feature distinguishing keratoconic corneas is ocular aberrations, manifesting up to five or six times the amount of higher-order aberrations than a normal, healthy eye. These aberrations can cause visual disturbances even at the very early stages of the disease. In the past, a diagnosis was derived from clinical symptoms, but technological advances have revealed multiple pre-clinical features, allowing for the differentiation between keratoconic and normal eyes at a much earlier stage. These include anterior and posterior corneal surface elevations, the corneal pachymetry profile, corneal epithelial patterns, wavefront aberration metrics, and corneal biomechanics (Sedaghat et al. in Sci Rep 11(1):11971, 2021).This review discusses the aberrations associated with keratoconus, how to measure them, and treatment methods to minimize their negative influence. Early diagnosis can lead to early treatment and may allow for arresting progression, thereby improving the long-term prognosis. With the acceleration of refractive surgery, it is important to identify patients with keratoconus, as they are usually contraindicated for refractive surgery.

Artificial Neural Network for Automated Keratoconus Detection Using a Combined Placido Disc and Anterior Segment Optical Coherence Tomography Topographer.

To assess the efficacy of an automated program for keratoconus and keratoconus suspect detection based on corneal measurements provided by a combined Placido disc and anterior segment optical coherence tomography (OCT) topographer. In a multicentric cross-sectional study, an artificial neural network (ANN) was created using 6677 eyes from an equal number of patients (classified as 2663 normal eyes, 1616 keratoconus eyes, 210 keratoconus suspect eyes, 1519 myopic postoperative eyes, and 669 abnormal eyes). Each group was randomly divided into a training set (70% of the dataset) and a validation set (the remaining 30%). A multilayer perceptron network with a backpropagation learning algorithm was developed for the study. Indexes used to train the ANN were based on curvature and elevation of both the anterior and posterior corneal surfaces and the new corneal OCT indexes-based on corneal, stromal, and epithelial thicknesses. For keratoconus detection, our ANN showed an accuracy of 98.6%, precision of 96%, recall of 97.9%, and F1-score of 96.9%. For keratoconus suspect detection, our ANN showed an accuracy of 98.5%, precision of 83.6%, recall of 69.7%, and F1-score of 76%. Compared to previous literature, the addition of new OCT-based epithelial and stromal thickness indexes improves ANN detection capacity of keratoconus suspect eyes. For already stablished keratoconus our ANN detection capacity is excellent, but equivalent to previous evidence without incorporating such new OCT-based indexes. OCT-based epithelial and stromal thickness indexes improve ANN detection capacity of keratoconus on its early stages.

Effects of graft detachment on the central corneal thickness after uncomplicated Descemet membrane endothelial keratoplasty

PurposeTo determine if early central corneal thickness (CCT) and best-corrected visual acuity (BCVA) changes indicate graft detachment after uncomplicated Descemet membrane endothelial keratoplasty (DMEK).MethodsIn this analysis of our prospectively collected ADDA registry data (https://drks.de/search/de/trial/DRKS00027180), 45 pseudophakic eyes underwent DMEK surgery at the Department of Ophthalmology, RWTH Aachen University. Anterior segment optical coherence tomography (AS-OCT), the presence of stromal ripples on the posterior corneal surface, and BCVA measurements were assessed prior to, 1 day, 1 week, 1 month, and 6 months after surgery.ResultsEyes were categorized into three groups: no graft detachment (group 1) (20/45; 44.4%), < 1/3 graft detachment (group 2) (14/45; 31.1%), ≥ 1/3 graft detachment followed by rebubbling (group 3) (11/45; 24.4%). Eyes in group 3 had a greater CCT prior to (746.8 ± 95.8 µm vs. 665.0 ± 74.4 µm, P = 0.041), and 1 week (666.8 ± 119.5 µm vs. 556.5 ± 56.8 µm, P = 0.001) after DMEK compared to group 1. By 1 month, CCT in all groups aligned. Comparing prior to and 1 week after DMEK, none of the eyes in group 1 had an increase in CCT, while the CCT increased in 25.0% of eyes in group 2 and 22.2% in group 3. In group 1, 90.0% had a CCT of < 600 µm 1 week after DMEK, compared to only 50.0% in group 2 and 36.4% in group 3. In group 1, 90.0% (18/20) had an improved BCVA 1 week after DMEK, while in groups 2 and 3, 86.7% (12/14) and 18.2% (2/11) improved, respectively. One patient in group 3 showed posterior stromal ripples 1 day and 1 week after DMEK.ConclusionIf 1 week after uncomplicated DMEK CCT is < 600 µm and has decreased from before surgery, BCVA has improved, and there are no posterior stromal ripples, a graft detachment ≥ 1/3 and the need for rebubbling are very unlikely. In all other cases, meticulous slit-lamp and OCT inspection of the peripheral graft for detachments should be advised.

Changes in posterior corneal elevation after small incision lenticule extraction for different myopic diopters.

To study the changes and effect factors of posterior corneal surface after small incision lenticule extraction (SMILE) with different myopic diopters. Ninety eyes of 90 patients who underwent SMILE were included in this retrospective study. Patients were allocated into three groups based on the preoperative spherical equivalent (SE): low myopia (SE≥-3.00 D), moderate myopia (-3.00 D>SE>-6.00 D) and high myopia (SE≤-6.00 D). Posterior corneal surfaces were measured by a Scheimpflug camera preoperatively and different postoperative times (1wk, 1, 3, 6mo, and 1y). Posterior mean elevation (PME) at 25 predetermined points of 3 concentric circles (2-, 4-, and 6-mm diameter) above the best fit sphere was analyzed. All surgeries were completed uneventfully and no ectasia was found through the observation. The difference of myopia group was significant at the 2-mm ring at 1 and 3mo postoperatively (1mo: P=0.017; 3mo: P=0.018). The effect of time on ΔPME was statistically significant (2-mm ring: P=0.001; 4-mm ring: P<0.001; 6-mm ring: P<0.001). The effect of different corneal locations on ΔPME was significant except 1wk postoperatively (1mo: P=0.000; 3mo: P=0.000; 6mo: P=0.001; 1y: P=0.001). Posterior corneal stability was linearly correlated with SE, central corneal thickness, ablation depth, residual bed thickness, percent ablation depth and percent stromal bed thickness. The posterior corneal surface changes dynamically after SMILE. No protrusion is observed on the posterior corneal surface in patients with different degrees of myopia within one year after surgery. SMILE has good stability, accuracy, safety and predictability.

CorNet: Autonomous feature learning in raw Corvis ST data for keratoconus diagnosis via residual CNN approach

PurposeTo ascertain whether the integration of raw Corvis ST data with an end-to-end CNN can enhance the diagnosis of keratoconus (KC). MethodThe Corvis ST is a non-contact device for in vivo measurement of corneal biomechanics. The CorNet was trained and validated on a dataset consisting of 1786 Corvis ST raw data from 1112 normal eyes and 674 KC eyes. Each raw data consists of the anterior and posterior corneal surface elevation during air-puff induced dynamic deformation. The architecture of CorNet utilizes four ResNet-inspired convolutional structures that employ 1 × 1 convolution in identity mapping. Gradient-weighted Class Activation Mapping (Grad-CAM) was adopted to visualize the attention allocation to diagnostic areas. Discriminative performance was assessed using metrics including the AUC of ROC curve, sensitivity, specificity, precision, accuracy, and F1 score. ResultsCorNet demonstrated outstanding performance in distinguishing KC from normal eyes, achieving an AUC of 0.971 (sensitivity: 92.49%, specificity: 91.54%) in the validation set, outperforming the best existing Corvis ST parameters, namely the Corvis Biomechanical Index (CBI) with an AUC of 0.947, and its updated version for Chinese populations (cCBI) with an AUC of 0.963. Though the ROC curve analysis showed no significant difference between CorNet and cCBI (p = 0.295), it indicated a notable difference between CorNet and CBI (p = 0.011). The Grad-CAM visualizations highlighted the significance of corneal deformation data during the loading phase rather than the unloading phase for KC diagnosis. ConclusionThis study proposed an end-to-end CNN approach utilizing raw biomechanical data by Corvis ST for KC detection, showing effectiveness comparable to or surpassing existing parameters provided by Corvis ST. The CorNet, autonomously learning comprehensive temporal and spatial features, demonstrated a promising performance for advancing KC diagnosis in ophthalmology.

Comprehensive Assessment of Posterior Corneal Asphericity Change Calculated by Tangential Radius of Curvature After FS-LASIK and SMILE.

To evaluate changes in posterior corneal asphericity (ΔQ) using the tangential radius of curvature after femtosecond laser-assisted in situ keratomileusis (FS-LASIK) and small incision lenticule extraction (SMILE) procedures. One hundred twenty right eyes of myopic patients who underwent either FS-LASIK or SMILE procedures were analyzed using Sirius 3D corneal topography for assessment. The tangential radius was employed to calculate both preoperative and postoperative posterior corneal Q-values across each semimeridian. After both surgical interventions, the ΔQ value variations across the 360° semimeridional regions of the posterior corneal surface were compared. A marked postoperative increase in the posterior corneal Q-value was documented. No significant differences were noted between the postoperative Q-values or ΔQ-values of the two surgical approaches. Among patients with moderate myopia, postoperative Q-value exhibited considerably lower increases and ΔQ-value significantly smaller than their counterparts with high myopia. Moreover, the fluctuation in ΔQ across semimeridional regions was less evident in patients with moderate myopia than in those with high myopia. Notably, the degree of ΔQ fluctuation across semimeridional regions was similar between both surgical categories. These data offer insights into variations in the posterior corneal surface after refractive surgeries depending on the degree of myopia, illuminating their clinical relevance. Both FS-LASIK and SMILE introduce notable changes to posterior corneal asphericity among patients with different myopia intensities. Furthermore, the influence on the asphericity across the entire posterior surface is similarly distributed between FS-LASIK and SMILE techniques. [J Refract Surg. 2024;40(3):e133-e141.].

Predictive factors for re-bubbling after DMEK: focus on the posterior corneal surface.

To understand whether the preoperative morphology of the posterior corneal surface influences the rate of re-bubbling after Descemet membrane endothelial keratoplasty (DMEK). After retrospectively analyzing the medical records of patients undergoing DMEK, in this multicentric cross-sectional study, we performed a binomial logistic regression analysis to assess significant predictors of re-bubbling and re-transplantation after surgery. Analyzed parameters included the preoperative diagnosis, anterior and posterior surface K1/K2, central corneal thickness, posterior Q value, and other posterior corneal surface parameters evaluated on the elevation maps produced by anterior segment optical coherence tomography. Results were stratified based on the surgeons' experience. We included 202 eyes of 202 patients with a mean age of 69.5 ± 12.4years; 154 eyes were operated by a high-volume surgeon and 48 by one with less experience; 48 eyes (23.8%) underwent 1 re-bubbling and 14(6.9%) 1 re-transplantation. The presence of positive/less-negative posterior corneal irregularities and irregularities with greater absolute height had a significantly higher risk of re-bubbling in both the expert and less expert group (OR = 2.85 and 1.42, OR = 3.22 and 3.01, respectively, p < 0.05), whereas more negative posterior K1 and K2 were significant risk factors only in the former group (OR = 0.67 and 0.55, respectively, p < 0.05). Endothelial decompensation other than Fuchs and pseudophakic bullous keratopathy, more negative posterior Q values and smaller distances between center, and the highest/lowest posterior corneal surface irregularity correlated with an increased risk of graft failure (OR 1.23, 1.21, and 1.29, respectively, p < 0.05). Posterior corneal surface morphology significantly influences the risk of re-bubbling after DMEK.

Changes in Corneal Higher-Order Aberrations and Ocular Biometric Measurements after Phacoemulsification Combined with Goniosynechialysis in Primary Angle Closure/Glaucoma Patients.

To compare corneal higher-order aberrations (HOAs), refractive error, and ocular biological parameters before and after phacoemulsification combined with goniosynechialysis (Phaco-GSL) in primary angle closure/glaucoma (PAC/PACG) patients with different axial lengths (ALs). In this prospective study, cataract patients diagnosed with PAC/PACG were categorized into two groups based on their ALs: the short AL group (AL ≤ 22.5 mm) and the normal AL group (22.5 < AL ≤ 24.5 mm). The pre- and postsurgery measurements of intraocular pressure (IOP) and best-corrected visual acuity (BCVA) were conducted at 1 day, 1 week, 1 month, 3 months, 6 months, and 12 months. Additionally, the assessments included corneal HOAs, the number of antiglaucoma medications, visual field parameters, manifest refraction, and other ocular biological parameters before surgery and at the final follow-up. Prior to surgery, the two groups exhibited no significant differences, except for AL, curvature value, and Z (4, 0) of the posterior corneal surface (all P < 0.01). Following surgery, BCVA improved, and IOP decreased significantly in both groups (P < 0.01). Both anterior and total corneal HOAs, along with Z (3, -3), increased in the two groups (all P < 0.05), with the normal AL group exhibiting a significantly greater increase in total cornea Z (3, -3) than the short AL group (P=0.047). The normal AL group also exhibited a slight tendency towards hyperopia (P < 0.01). Significant changes were observed in the visual field index and mean deviation in both groups (P < 0.05). Phaco-GSL resulted in an increased corneal HOAs, particularly trefoil, with variations based on the patient's AL. Patients with normal ALs tended to shift towards hyperopia after surgery.