Keratoconus Grade Research Articles

Partial reconstruction of sparse and incomplete point clouds applied to the generation of corneal topographic maps of healthy and diseased patients

The presence of unmeasured areas or areas with missing data in corneal topographies greatly affect the quality of digital corneal models. These are more frequent in posterior than in anterior corneal surface. This work seeks to complete and improve digital corneal models generated from incomplete point clouds obtained with commercial tomographic equipment, applying three interpolation/extrapolation techniques based on population data (Polynomial, Biharmonic Splines and Cubic Radial Base Functions). 43 personalized corneal models of patients with different grades of keratoconus were used to test each interpolation method. All interpolation results were compared using the Mean Average Percentage Error (MAPE) index, observing that it is possible to interpolate/extrapolate up to the radius 5.2 mm on the anterior face and up to 4.2 mm on the posterior face in general, but none of the methods stand out above the others for all the situations considered. Consequently, extrapolation method must be chosen carefully.

Repeatability of Epithelium Thickness Measured by an AS-OCT in Different Grades of Keratoconus and Compared to AS-OCT/Placido Topography

To compare agreement of corneal epithelium thickness (ET) between AS-OCT system (RTVue, Optovue) and AS-OCT/Placido topographer (MS-39, CSO) in eyes with different stages of keratoconus (KC), and to assess the repeatability of RTVue AS-OCT. Prospective reliability analysis. KC eyes were classified into forme fruste KC (FFKC), mild, moderate, and severe KC. Agreement was evaluated with Bland-Altman plots and 95% limits of agreement (LoA). The repeatability of RTVue was assessed via within-subject standard deviation (Sw), test-retest variability (TRT), coefficient of variation (CoV), and intraclass correlation coefficient (ICC). A total of 119 KC eyes were enrolled, with 21 being FFKC, 26 mild, 39 moderate, and 34 severe. The 95% LoA ranged between -5.9 and 4.8 µm for center epithelium thickness (CET), between -5.7 and 8.2 µm for thinnest epithelium thickness (TET). At 1-mm measuring points, the 95% LoA of superior, inferior, nasal, and temporal were -4.2 to 4.7 µm, -5.2 to 6.0 µm, -7.9 to 10.2 µm, and -11.2 to 6.0 µm. At 3-mm measuring points, the corresponding values were -2.8 to 9.3 µm, -2.0 to 13.0 µm, -4.6 to 9.6 µm, and -6.3 to 9.7 µm, indicating that the 2 instruments were not interchangeable without adjustment. Despite that the repeatability of RTVue measurements in KC patients were acceptable, repeatability decreased gradually with the peripheralization of the measurement points. The 2 OCT-based devices, RTVue and MS-39, do not provide interchangeable measurements of epithelium thickness in KC patients. Repeatability decreases in cases of more severe KC, emphasizing the importance of grading before clinical examination to avoid diagnostic errors.

Assessing progression limits in different grades of keratoconus from a novel perspective: precision of measurements of the corneal epithelium

BackgroundTo assess repeatability and reproducibility of corneal epithelium thickness (ET) measured by a spectral-domain optical coherence tomographer (SD-OCT)/Placido topographer (MS-39, CSO, Florence, Italy) in keratoconus (KC) population at different stages, as well as to determine the progression limits for evaluating KC progression.MethodsA total of 149 eyes were enrolled in this study, with 29 eyes in the forme fruste keratoconus (FFKC) group, 34 eyes in the mild KC group, 40 eyes in the moderate KC group, and 46 eyes in the severe KC group. Employing the within-subject standard deviation (Sw), test-retest variability (TRT), coefficient of variation (CoV), and intraclass correlation coefficient (ICC) to evaluate intraoperator repeatability and interoperator reproducibility.ResultsThe repeatability and reproducibility of MS-39 in patients with KC were acceptable, according to ICC values ranging from 0.732 to 0.954. However, patients with more severe KC and progressive peripheralization of the measurement points had higher TRTs but a thinning trend. The current study tended to set the cut-off values of mild KC, moderate KC, and severe KC to 4.9 µm, 5.2 µm, and 7.4 µm for thinnest epithelium thickness (TET). When differences between follow-ups are higher than those values, progression of the disease is possible. As for center epithelium thickness (CET), cut-off values for mild KC, moderate KC, and severe KC should be 2.8 µm, 4.4 µm, and 5.3 µm. This might be useful in the follow-up and diagnosis of keratoconus.ConclusionsThis study demonstrated that the precision of MS-39 was reduced in measuring more severe KC patients and more peripheral corneal points. In determining disease progression, values should be differentiated between disease-related real changes and measurement inaccuracies. Due to the large difference in ET measured by MS-39 between various stages of disease progression, it is necessary to accurately grade KC patients to avoid errors in KC clinical decision-making.

Outcomes of the Q value-based nomogram in managing pediatric versus adult keratoconus: a prospective interventional study.

Keratoconus (KCN) is an ectatic disorder of the cornea characterized by stromal weakness and apical protrusion of the cornea, and is associated with a gradual and painless reduction in visual acuity. KCN in pediatric patients has certain important characteristics, such as a progressive and aggressive nature. We aimed to analyze the visual, refractive, and topographic outcomes of implanting a single 210° arc-length Keraring segment according to a novel, objective, Q value-based nomogram (Q-N) for the treatment of pediatric versus adult KCN. This prospective, multicenter, non-randomized, open-label trial included 47 eyes of 47 patients who were allocated to one of two groups. The adult group included 33 eyes of patients ≥ 18 years of age, whereas the pediatric group included 14 eyes of patients aged 14 - 17 years. All patients underwent femtosecond laser-assisted implantation of a single 210° arc-length Keraring segment according to the Q-N and were followed up for 6 months. All eyes underwent visual acuity measurement, cycloplegic refraction, and corneal topography at baseline and 6 months after surgery. The study groups were comparable in terms of sex proportions and KCN grades (both P > 0.05). The adult group exhibited significant postoperative improvements in mean uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), sphere, cylinder, spherical equivalent (SE), and Kmax (all P < 0.001) with a mean change of -0.56 logarithm of the minimal angle of resolution (logMAR), - 0.40 logMAR, 3.07 diopters (D), 0.70 D, 3.42 D, and - 5.26 D, respectively. The pediatric group exhibited significant postoperative improvements in mean UDVA, CDVA, sphere, SE, and Kmax (all P < 0.05) with a mean change of - 0.62 logMAR, - 0.34 logMAR, 3.18 D, 3.67 D, and - 5.37 D, respectively. There were no significant differences between the groups in terms of the mean change in visual, refractive, and topographic variables (all P > 0.05). No postoperative complications were observed in either group. Use of the objective Q-N was efficient in the treatment of pediatric KCN, with postoperative improvements in the mean visual, refractive, and topographic parameters, comparable to outcomes in adult keratoconus. Q-N achieved good corneal remodeling with subsequent improvements in visual, refractive, and topographic outcomes in both adult and pediatric patients with keratoconus. To verify our preliminary findings, we recommend further multicenter randomized clinical trials using the Q-N nomogram in a larger sample of pediatric patients with KCN as an adjunct treatment before or after CXL.

Prediction of total corneal power in keratoconus using anterior surface data

ABSTRACT Clinical relevance Keratoconus results in an increase in anterior and posterior curvatures and a reduction in corneal thickness. Anterior corneal ectasia is partially compensated by remodelling the corneal epithelium. Therefore, there is an alteration in the relationship between corneal surfaces and variation in corneal power. The variation in corneal power is one of the sources that induces errors in IOL power calculation. Background This study aimed to assess a method for predicting total corneal power in keratoconus using several anterior surface parameters at 3 mm and 4 mm. Methods Tomographic data obtained using Pentacam (Oculus, Germany) were analysed from 280 eyes of 140 patients with keratoconus using anterior and posterior keratometry, anterior Q-value at 8 mm, central corneal thickness, Kmax location and value, and true net power at 4 mm (TNP). Calculated total corneal power (TCPc) at 3 mm was obtained using the Gauss formula. Predicted total corneal power at 3 mm (TCPp3) and 4 mm (TCPp4) was obtained from univariate (TCPp3u and TCPp4u) and multivariate linear regression formulae (TCPp3m and TCPp4m). SimK, anterior Q-value, vertical location, and Kmax value were used in the multivariate formulae. Mean absolute error (MAE) and median absolute error (MedAE) were also calculated. Absolute frequencies within dioptric ranges of all formulas divided for keratoconus grading were evaluated. Results TCPc and TNP exhibited a good correlation (R2 = 0.58, p < 0.05) with a higher dispersion above 50 D of corneal power. Highly significant correlations were observed between TCPp3u and TCPc (R2 = 0.978, p < 0.05) and TCPp3m and TCPc (R2 = 0.989, p < 0.05). Lower but significant correlations were observed between TCPp4u and TNP (R2 = 0.692, p < 0.05) and between TCPp4m and TNP (R2 = 0.887, p < 0.05). The best results for TCP prediction at 3 and 4 mm were obtained with TCPp3m and TCPp4m as follows: MAE of TCPp3m was 0.24 ± 0.20 (SD) D with MedAE of 0.20 D, while MAE of TCPp4m was 0.96 ± 0.77 D with MedAE of 0.80 D. The 3 mm multivariate regression formula results in higher absolute frequencies of prediction errors in the total eyes within 0.5 D (93%) than the univariate formula (81%). At 4mm, the multivariate regression formula has a lower percentage within 0.5 D (32%) than the univariate formula (41%), but the percentage of the multivariate formula is higher within 1 D (63%) than the univariate formula (56%). Conclusion All formulas show a decrease in accuracy with increasing grades of keratoconus. Multivariate linear regression formulae using only anterior surface data can predict TCP with good approximation in eyes with keratoconus in cases where posterior surface parameters are unavailable. The vertical location of Kmax and the anterior asphericity could play a relevant role in the prediction of total corneal power in keratoconus.

Analysis of the outcomes of three different cross-linking protocols for treatment of paediatric keratoconus: A multicentre randomized controlled trial.

To analyse long-term outcomes of standard cross-linking (SCXL), accelerated cross-linking (ACXL) and transepithelial cross-linking (TCXL) in the treatment of progressive paediatric keratoconus regarding stability, safety and efficacy. This prospective multicentre randomized controlled trial included 97 eyes of 97 paediatric patients with stages I-III ABCD keratoconus grading system, who were randomized into three groups; SCXL group (control group, n = 32; 3 mW/cm2 × 30 min/5.4 J/cm2 ), ACXL (n = 33; 18 mW/cm2 × 5 min/5.4 J/cm2 ) and TCXL (n = 32; 18 mW/cm2 × 5 min/5.4 J/cm2 ). Subjective refraction, uncorrected and corrected visual acuity, keratometry and pachymetry measurements using corneal topography were recorded preoperatively and 1, 2 and 3 years postoperatively. SCXL group exhibited significant successive improvements in the mean visual, refractive and keratometric parameters throughout the entire postoperative 3 years while ACXL group exhibited significant improvements in visual and keratometric parameters in the first postoperative year that remained stable in second and third postoperative years. TCXL group exhibited significant progressive deterioration in all mean parameters compared to SCXL and ACXL (p < 0.0001). Both SCXL and ACXL revealed final 100% success rate with good stability while TCXL revealed final 22% failure rate with keratoconus progression (p < 0.0001). SCXL and ACXL were comparable in halting keratoconus progression and achieved good stability and safety; however, SCXL was more efficient than ACXL as it yielded greater significant postoperative mean visual, refractive and keratometric improvements achieving smoother corneal remodelling. Both SCXL and ACXL were much superior to TCXL. SCXL is the best CXL treatment option for paediatric keratoconus while ACXL is a good and effective alternative.

Changes in corneal biomechanical parameters in keratoconus eyes with various severities after corneal cross-linking (CXL): A comparative study.

To compare changes in corneal biomechanical parameters one year after corneal cross-linking (CXL) in keratoconus (KCN) eyes of different severities. Seventy-five eyes with mild, moderate, and severe grades of KCN (n = 24, 31, and 20 eyes, respectively) that were treated with CXL, based upon the standard Dresden protocol, were included. The corneal biomechanical assessment was performed using Corvis ST and Ocular Response Analyzer (ORA). Changes in Corvis's dynamic corneal response (DCR) parameters and ORA's derived parameters (corneal hysteresis (CH), and corneal resistance factor (CRF)) were assessed whilst the corneal thickness and intraocular pressure were considered as covariates. There was no statistically significant difference in the corneal biomechanical parameters obtained using both devices after surgery separately in different KCN grades, except for the deformation amplitude (DA) in the severe KCN group (P = 0.017). Changes in the classic parameters of the highest concavity phase of Corvis ST (peak distance, radius, and DA) were more positive and in the newer parameters (integrated inverse radius (IIR), deformation amplitude ratio (DAR)) more negative in the severe group compared to the other groups. Also, the mean change in CH (P = 0.710), and CRF (P = 0.565), showed a negative shift in higher grades of KCN; however, there was no significant difference in the mean changes of all parameters between different groups. (P > 0.05). Similar changes in the Corvis ST and ORA parameters in mild, moderate, and severe KCN indicate biomechanical stability and the effective role of CXL in stopping the progressive nature of keratoconus in eyes of varying severities one year after CXL.

Distribution of corneal densitometry in different grades of keratoconus.

To evaluate the use of Scheimpflug tomography in corneal densitometry (CD) in comparing the stages of keratoconic eyes. Keratoconic (KC) corneas (stages 1-3 classified according to the topographic parameters) were examined using the Scheimpflug tomographer (Pentacam, Oculus) using the CD software. CD was measured over three different depths (anterior stromal layer [120 μm], posterior stromal layer [60 μm], and middle stromal layer between these two layers), and concentric annular zones (0.0 to 2.0, 2.0 to 6.0, 6.0 to 10.0, and 10.0 to 12.0 mm diameter area). The study participants were divided into three groups: keratoconus (KC) stage 1 (KC1) with 64 participants, keratoconus stage 2 (KC2) with 29 participants, and keratoconus stage 3 (KC3) with 36 participants. Comparing CD of all three layers (anterior, central, and posterior) of the cornea over different circular annuli (0-2, 2-6, 6-10, and 10-12 mm) revealed a significant difference in the 6-10 mm annulus between all groups and in all layers (P = 0.3, 0.2, and 0.2, respectively). Area under curve (AUC) was done. It revealed that the central layer showed the highest specificity (93.8%) in comparing KC1 and KC2, whereas CD in the anterior layer between KC2 and KC3 had the highest specificity (86.2%). CD showed increased values in the anterior corneal layer and in the annulus 6-10 mm more than other locations in all stages of KC.

LKG-Net: lightweight keratoconus grading network based on corneal topography.

Keratoconus (KC) is a noninflammatory ectatic disease characterized by progressive thinning and an apical cone-shaped protrusion of the cornea. In recent years, more and more researchers have been committed to automatic and semi-automatic KC detection based on corneal topography. However, there are few studies about the severity grading of KC, which is particularly important for the treatment of KC. In this work, we propose a lightweight KC grading network (LKG-Net) for 4-level KC grading (Normal, Mild, Moderate, and Severe). First of all, we use depth-wise separable convolution to design a novel feature extraction block based on the self-attention mechanism, which can not only extract rich features but also reduce feature redundancy and greatly reduce the number of parameters. Then, to improve the model performance, a multi-level feature fusion module is proposed to fuse features from the upper and lower levels to obtain more abundant and effective features. The proposed LKG-Net was evaluated on the corneal topography of 488 eyes from 281 people with 4-fold cross-validation. Compared with other state-of-the-art classification methods, the proposed method achieves 89.55% for weighted recall (W_R), 89.98% for weighted precision (W_P), 89.50% for weighted F1 score (W_F1) and 94.38% for Kappa, respectively. In addition, the LKG-Net is also evaluated on KC screening, and the experimental results show the effectiveness.

Angle κ and its effect on the corneal elevation maps in refractive surgery candidates.

To assess the associations of angle κ and Pentacam decentration indices with elevation maps in normal refractive surgery candidates. Salouti Cornea Research Center, Salouti Eye Clinic, Shiraz, Iran. Retrospective observational study. In this research, the right eyes of 173 refractive surgery candidates were assessed. Data of front and back corneal elevation maps, keratometric data, decentration indices, and corneal astigmatism obtained by Pentacam HR system and angle κ obtained by Orbscan IIz were extracted. Maximum elevation (or depression) for each of the 4 quadrants was recorded. Correlations of elevation values with angle κ, Pentacam decentration indices, keratometry, and astigmatism were examined by Pearson correlation coefficient. 148 age- and sex-matched cases with keratoconus grade 1 were selected as a positive control group, and Pentacam variables were compared between the groups. Overall, data from 173 eyes of 173 normal refractive surgery candidates and 148 eyes of 148 patients with keratoconus were recorded and analyzed. In normal refractive surgery candidates, the mean of angle κ was 5.32 ± 1.36 (SD) degrees. Angle κ had a positive correlation with front and back temporal elevations based on a best-fit sphere (BFS) ( r = 0.339, P = .001; r = 0.300, P < .001, respectively). Front and back keratometric astigmatisms were positively correlated with front and back nasal and temporal elevations ( r ≥ 0.543, P < .001) and negatively correlated with superior and inferior elevations ( r ≤ -0.547, P < .001). These associations no longer existed when using best-fit toric ellipse (BFTE) for calculating elevation data. The thinnest point to vertex decentration was significantly associated with the back temporal elevation (based on the BFTE) in both normal ( r = 0.311, P < .001) and keratoconus ( r = 0.190, P = .021) eyes. This study showed that elevation maps obtained by the Pentacam system using BFS might be affected by both the large angle κ and corneal astigmatism, confounding the preoperative assessment of refractive surgery candidates. Using BFTE as a reference for calculating elevation data should eliminate most diagnostic issues and thus is encouraged in this context.

High-frequency ultrasound detects biomechanical weakening in keratoconus with lower stiffness at higher grade.

In vivo biomechanical characterization of the cornea remains a challenge. We have developed a high-frequency ultrasound elastography method, the ocular pulse elastography (OPE), to measure corneal axial displacement (CAD) induced by the ocular pulse. Here we compared CAD and a stiffness index derived from CAD between keratoconus patients and normal controls. We also explored the trend of these parameters with keratoconus grade. Twenty normal subjects and twenty keratoconus patients were recruited in this study. Corneal topography, tomography, intraocular pressure (IOP) and ocular pulse amplitude (OPA) were obtained in each measured eye. The cornea’s heartbeat-induced cyclic axial displacements were measured by high-frequency (50 MHz) ultrasound. A corneal stiffness index (CSI) was derived from CAD normalized against OPA. CAD and CSI were compared between normal and keratoconus groups, and across keratoconus grades. Keratoconus corneas had significantly greater CAD and lower CSI than normal controls (p’s<0.01). Both parameters correlated strongly with grade, in which CAD increased significantly (p = 0.002) and CSI decreased significantly (p = 0.011) with grade. These results suggested a biomechanical weakening in keratoconus which worsens at higher disease severity. This study also demonstrated the ability of high-frequency ultrasound elastography to provide a safe, quick, and accurate evaluation of the cornea’s biomechanical condition in vivo. The OPE-measured biomechanical metrics, when integrated with existing diagnostic criteria, may aid the decision-making in the early and definitive diagnosis and staging of keratoconus.

Keratoconus. Its prevalence and severity in spring catarrh patients. A Perspective study.

Objectives: To find out the prevalence and severity of keratoconus in spring catarrh patients. Study Design: Descriptive and Perspective study. Setting: OPD K.D.A Teaching Hospital Kohat. Period: March 2017 to October 2019. Material &amp; Methods: All patients suffering from spring catarrh were included in the study after consent. Proper proforma was designed for record. Detail history was taken and for diagnosis all the patients were properly examined with slit lamp. Visual acuity was checked. Radioscopy for irregular scissor reflex and fundoscopy for oil droplet sign for keratoconus was carried out. Keratometry was done to determine the astigmatism and severity of keratoconus Grading of keratoconus was done by the highest axis of corneal power on keratometry as mild (&lt; 48 D), moderate (48-54 D) and severe (&gt; 54 D). Suspected cases were advised corneal topography. Total 480 patients were included in the study. Out of these 480 patients 295 (61.45%) were male and 185 (38.54%) female. The age range of patients was 9 to 37 years. Results: Out of 480 patients, 47(9.79%) patients had keratoconus in which 36(76.59%) were male and 11(23.40%) were female. Out of 47 patients 19 (40.42%) had mild, 22(46.80%) had moderate and 6(12.76%) patients had severe keratoconus. Conclusion: Keratoconus has strong association with spring catarrh.

Astigmatic change as a predictor of intrastromal corneal ring segment late extrusion.

To evaluate changes in keratoconic corneas implanted with intrastromal corneal ring segments (ICRSs) that have been explanted because of late extrusion of the segment after >2 years. Vissum Miranza, Alicante, Spain; OftalmoSalud, Lima, Peru; Minya University Hospital, Egypt. Retrospective multicenter case series. 23 keratoconic corneas that were implanted for ≥2 years and explanted because of natural extrusion of the segment. Clinical measures of visual, refractive, topographic, pachymetric, and aberrometric data were analyzed. To perform exploratory factor analysis, the Kaiser-Meyer-Olkin (KMO) test was used to evaluate sampling adequacy. Factor analysis with VARIMAX rotation was used to determine the main factors of the inventory. The mean time interval was 5 years. Topographic findings were reversed nearly to the baseline level after segment explantation (Km: 48.97 ± 3.47 D pre implantation and 47.60 ± 3.67 D after explantation, P =.374). Significant worsened in refractive cylinder was found pre-ICRS extrusion (‒2.54 ± 3.40 D after implantation and ‒3.96 ± 1.72 before extrusion, P < .05). The main factor obtained in the preimplantation moment included keratoconus grade, keratometric readings, and visual acuities. After ICRS implantation, the most strength components were the refractive cylinder, corrected distance visual acuity, and uncorrected distance visual acuity. Corneal aberrations were the main factors in the pre-explantation analysis. ICRSs were safely extracted, with a reversal of the corneal topographic data to the preoperative level. A significant astigmatic change was shown in patients implanted with ICRSs before late extrusion of the segment, suggesting the role of this parameter as a prognostic factor of extrusion.

Evaluation and Comparison of Posterior Corneal Elevation Parameters in Different Grades of Keratoconus by Pentacam

To evaluate and compare posterior corneal elevation data and anterior segment parameters in different grades of keratoconus by Pentacam. 114 eyes of 114 keratoconic patients (85 men and 56 women) with a mean age of 31.6±4.7 years were evaluated with a Pentacam Scheimpflug camera. Keratoconic eyes were divided into 3 groups or grades according to the maximum keratometry reading: mild or grade I (K=50 or less than 50 diopters [D]), moderate or grade II (K=50.0 to 55.0 D), and severe or grade III (K=55.0 D or higher). The posterior corneal parameters were obtained posterior. There were no statistically significant differences between keratoconus grades in terms of sex (P=0.661). Also, there were no statistically significant differences between 3 grades in terms of age (P=0.214). There were statistically significant differences in anterior keratometry readings (K), anterior chamber depth (ACD), anterior chamber angle (ACA), and all pachymetric corneal measurements between all groups. With the progression of the disease, posterior K readings and all posterior elevation measurements were statistically different between the three grades. However, there were no significant differences in pupil diameter, anterior chamber volume (ACV), and corneal volume (CV) between the three grades of keratoconus. According to the results of this study, height data of posterior elevation, when combined with corneal anterior segment parameter, could provide a useful keratoconus severity classification tool.

Investigation of Mitophagy Biomarkers in Corneal Epithelium of Keratoconus Patients

PurposeThe pathological mechanisms of keratoconus (KC) have not been elucidated yet. Mitophagy is an important mechanism that eliminates damaged mitochondria under oxidative stress, and it could be one of the leading pathological causes of KC. This study aimed to find out the role of mitophagy in the keratoconic corneal epithelium.MethodsThe corneal epithelia were collected from the 103 progressive KC patients and the 46 control subjects. The real-time quantitative PCR was performed for PTEN-putative kinase-1 (PINK1), PARKIN, p62, and BNIP3 gene expressions in 31 KC and 9 control subjects. Western blot analyses were performed to investigate the protein expressions of PINK1, PARKIN, LC3B, ATG5, and BECLIN in the remaining 109 corneal epithelium samples from 72 patients and 37 control subjects.ResultsmRNA and protein expressions of PINK1 decreased significantly in the corneal epithelium of KC patients compared to the control subjects. No significant change was found in mRNA levels of PARKIN, p62, and BNIP3 in KC patients. The protein expression of PARKIN, LC3B, ATG5, and Beclin did not significantly differ between KC patients and control subjects. Gene expression levels of mitophagy biomarkers were not affected by the KC grade.ConclusionsPINK1/PARKIN-dependent mitophagy is affected in the keratoconic corneal epithelium. We found significant decreases in both mRNA and protein expressions of PINK1 in the keratoconic corneal epithelium. However, we did not observe any other significant change in mitophagy markers. Mitochondrial stress-related mitophagy pathways could be interrupted by the decreased levels of PINK1 in the keratoconic corneal epithelium, but solely PINK1 dysregulation is not likely to induce KC pathogenesis.

Prognostic Nomograms Predicting Risk of Keratoconus in Very Asymmetric Ectasia: Combined Corneal Tomographic and Biomechanical Assessments.

Purpose: The aim of the study was to develop and validate a prognostic nomogram for subclinical keratoconus diagnosis using corneal tomographic and biomechanical integration assessments. Design: This is a retrospective case–control study. Methods: Setting: The study was carried out in a hospital setting. Patients: The study included patients with very asymmetric ectasia (VAE) and normal controls. Patients with VAE had defined clinical ectasia in one eye and normal topography (VAE-NT) in the fellow eye, and VAE-NT eyes were selected for analysis. VAE-NT was defined as stratified stage 0 using the ABCD keratoconus grading system. The normal control group was selected from corneal refractive surgery candidates at our clinic, and the right eye was enrolled. Observation Procedures: Scheimpflug-based corneal tomography (Pentacam) and corneal biomechanical assessment (Corvis ST) were performed. Main Outcome Measures: We performed multiple logistic regression analysis and constructed a simple nomogram via the stepwise method. The receiver operating characteristic (ROC) curve and discrimination and calibration of prognostic nomogram were performed by 500 bootstrap resamplings to assess the determination and clinical value, respectively. Results: A total of 59 VAE-NT and 142 normal eyes were enrolled. For differentiating normal and VAE-NT eyes, the values of specificity, sensitivity, and area under the ROC (AUROC) were 0.725, 0.610, and 0.713 for tomographic parameters, 0.886, 0.632, and 0.811 for biomechanical parameters, and 0.871, 0.754, and 0.849 for combined parameters, respectively. Combined parameters showed better predictability than separated tomographic or biomechanical parameters. Conclusion: Our nomogram developed with combined tomographic and biomechanical parameters demonstrated a plausible, capable, and widely implementable tool to predict risk of keratoconus. The identification of at-risk patients can provide advanced strategies to epitomize ectasia susceptibility.

Prevalence and topographical characteristics of keratoconus as a type of corneal ectasia among adult Egyptians with refractive errors

ObjectivesTo determine the prevalence of keratoconus (KC) among Egyptian adult population.BackgroundCorneal ectasia is a noninflammatory, bilateral, asymmetrical condition, causing progressive corneal steepening and thinning. KC is the most prevalent form of corneal ectasia and affects all ethnicities.Patients and methodsA cross-sectional study was conducted on 1607 adults at an Egyptian Governorate aged more than 18 years with high myopia of above − 6 D and high astigmatism above − 3 D old at some public and private ophthalmology centers, in Lower Egypt during the period from May 2020 till February 2021. Evaluation of corneal topography (Scheimpflug tomographer imaging system) and detection of any ectatic corneal conditions by corneal topography and analysis of their associated abnormal corneal parameters.ResultsThis study included 1607 patients, out of which 173 (10.8%) patients were diagnosed as having KC in one or both eyes. KC was more prevalent in right eyes (12.4%) than left ones (7.09%). The mean thickness of the thinnest corneal location (Mm) was significantly lower in the affected eyes (P < 0.001). K1, K2, Kmax, and anterior and posterior cornel maps were significantly increased among patients with KC4 than other different KC types. There was a significant negative correlation between KC grade and the thinnest location (r=−0.430, P < 0.001), and positive correlation between K1 (r = 0.274, P < 0.001), K2 (r = 0.391, P < 0.001), Kmax (r = 0.452, P < 0.001), anterior cornel map (r = 0.307, P < 0.001), and posterior cornel map (r = 0.306, P < 0.001) in eyes with KC.ConclusionThe KC is prevalent among Egyptian adults. Most cases had bilateral affection. Astigmatism was the most common refractive error being associated with KC with no statistically significant differences regarding sex or age.

Comparative analysis of the morphological and biomechanical properties of normal cornea and keratoconus at different stages

PurposeTo compare the morphological and biomechanical properties of normal cornea and keratoconus at different stages.MethodsA total of 408 patients (517 eyes) with keratoconus were included in this study. According to the Topographic Keratoconus (TKC) grading method, keratoconus was divided into stage I (TKC = 1, 130 eyes), stage II (TKC = 1–2, 2, 164 eyes), stage III (TKC = 2–3, 3, 125 eyes) and stage IV (TKC = 3–4, 4, 98 eyes). A total of 158 normal subjects (158 eyes) were recruited as the normal group. The corneal morphological parameters and biomechanical parameters were obtained with Scheimpflug tomography (Pentacam) and corneal visualization Scheimpflug technology (Corvis ST), and the receiver operating characteristic (ROC) curves were drawn.ResultsEach corneal morphological and most biomechanical parameters of the keratoconic eyes were significantly different from those of the normal eyes in this study (p < 0.001). ROC curve demonstrated that most parameters in this study showed high efficiency in diagnosing keratoconus (the area under the ROC (AUC) was > 0.9), with the Belin-Ambrósio deviation (BAD-D) and Tomographic and Biomechanical Index (TBI) showing higher efficiency. The efficiency of BAD-D and TBI was high in differentiating keratoconus at different stages (AUC > 0.963). The comparison of ROC curves of keratoconus at different stages did not reveal statistically significant differences for TBI.ConclusionBAD-D and TBI can effectively diagnose stage I keratoconus. Moreover, the efficiency of TBI is the same in diagnosing keratoconus at all stages, while the diagnostic efficiency of other parameters increases with the increase in keratoconus stages.

Long-Term Visual, Refractive and Topographic Outcomes of KeraRings Combined with Accelerated Transepithelial Crosslinking for Management of Different Grades of Progressive Keratoconus: A Retrospective Cohort Study

Purpose: To evaluate long-term visual, refractive, and topographic outcomes of KeraRings intrastromal implantation combined with accelerated transepithelial cross-linking for management of different stages of progressive keratoconus. Materials and Methods: This retrospective cohort study included 70 eyes of 70 patients with Amsler-Krumeich grades 1 to 4 keratoconus. They were divided into two groups: group-A included 37 eyes with grades 1-2 keratoconus, and group-B included 33 eyes with grades 3-4 keratoconus. Both groups underwent combined Keraring implantation with TCXL treatment. The main outcome measures included the preoperative and postoperative visual acuity, refraction, keratometry readings, and pachymetry. Results: At postoperative month 60, group-B exhibited significantly higher values of all mean uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), sphere/cylinder/spherical equivalent/defocus equivalent (DEQ), and K1/K2/Kaverages/Kmax parameters compared to that of group A. However, group-A exhibited better stability of postoperative improvements. Keratoconus progression (KCP) was greater in group-B (45.5%) than group-A (10.8%). Two eyes revealed segments' migration while one eye showed tunnel vascularization and opacification with segments' migration. Conclusion: The diagnostic criteria of preoperative-KCP are not adequate for the diagnosis of postoperative-KCP following ICRS implantation. UDVA and K average posterior seemed to be more sensitive parameters than K max in documenting early postoperative-KCP. We suggest that deterioration of UDVA≥0.10 log MAR and/or K average posterior ≥0.25 D are highly suspicious of post-ring implantation keratoconus progression (PR-KCP). The occurrence of two of the following parameters: Kmax≥0.50 D, Kaverageanterior≥0.50 D, K average posterior ≥0.25 D, or pachymetry≥1.5% thinning, is diagnostic of PR-KCP. The occurrence of two or more of the following parameters: Kmax≥0.50 D, Kaverageanterior≥0.50 D, Kaverageposterior ≥0.25 D, pachymetry≥ 1.5% thinning or UDVA≥0.10 logMAR, is diagnostic of PR-KCP. We also suggest that Kmax≥0.75 D alone is diagnostic of PR-KCP.

Agreement of keratometric readings measured using rotating Scheimpflug imaging, auto-refractokeratometer, and biograph in eyes with keratoconus.

To determine agreement in keratometric readings obtained using rotating Scheimpflug imaging with Pentacam, biograph with Lenstar LS900, and Topcon KR-8100P auto-keratorefractometer in eyes with different stages of keratoconus. A total of 89 eyes of 58 patients with keratoconus were examined in this study, retrospectively. The eyes were divided into two groups: mild group (group 1: 42 eyes) (Amsler-Krumeich stage 1) and moderate-to-severe group (group 2: 47 eyes) (Amsler-Krumeich stage 2, 3, 4). The keratometric readings measured using the Pentacam Scheimpflug system, Lenstar LS900, and Topcon KR-8100P auto-keratorefractometer were compared between the groups. The effects of the measurements of anterior chamber depth, Q value, axial length, central corneal thickness (CCT), and maximum value of keratometry (Kmax) on the differences of devices for keratometric readings were investigated. The mean values of the keratometric readings obtained using the Lenstar were steeper than with the Pentacam and Topcon, especially in group 2. In group 1, the mean K2 values measured using the Lenstar were significantly steeper than with the Topcon (p < 0.05); however, the devices were accordant for the other keratometric readings. In group 2, there was an agreement between the Pentacam and Topcon for the mean K1 and Km values; however, there were significant differences between the devices for the other values. The Q value and CCT had a negative correlation, and Kmax had a positive correlation with the differences of Lenstar-Pentacam and Lenstar-Topcon (p < 0.01). According to our results, Pentacam-Topcon and Pentacam-Lenstar can be used interchangeably for keratometry in mild stages of keratoconus. The keratometric readings of Lenstar were found steeper than the other devices with increasing grades of keratoconus. None of these devices can be used interchangeably in moderate-to-severe stages of keratoconus.