Keratoconic Eyes Research Articles

Cornea Confocal Microscopy Study of Patients with Preclinical Keratoconus

Purpose: To report the difference of corneal confocal microscopy examination in patients with preclinical keratoconus or clinical keratoconus. Methods: 8 unilateral keratoconus patients were examined by confocal microscopy before they had cross-linking surgery. As control groups, 23 patients with myopia and 13 patients with keratoconus in both eyes were also examined by confocal microscopy. Then we used Image J to compared the density of epithelium cell, length of cornea nerve fiber, density of Langerhans cell, density of keratocyte in shallow, middle, deep stroma, and the width and grayscale value of fold near Descement membrane for each group. Result: There was differences in corneal epithelial cell count between three groups (4358.27 ± 635.14 cells/mm² versus 4057.81 ± 316.29 cells/mm² versus 3522.65 ± 978.10 cells/mm²). The density of keratocyte in stroma showed a tendency to decrease with increasing depth. The density of keratocyte in keratoconus was less than that in normal eyes. The fold showed much wider and daker in keratoconus eyes than in normal eyes. The density of Langerhans cell was more in keratoconus group than it in normal group. Conclusion: We first report the differences in corneal epithelial cell count and fold near Descement membrane. It might provide a new way to diagnose early keratoconus. The difference of density of Langerhans cell suggested us the possibility of inflammation in keratoconus.

Repeatability and comparison of Corvis ST parameters before and after accelerated transepithelial corneal cross-linking in keratoconus eyes

AIM: To evaluate the repeatability and comparison of corneal visualization scheimpflug technology (Corvis ST) parameters in keratoconus eyes before and after accelerated transepithelial corneal cross-linking (ATE-CXL). METHODS: Thirty eyes of 30 progressive keratoconus patients were included in the prospective study. Three repeated corneal biomechanical measurements were performed preoperatively and one month postoperatively by Corvis ST. The interclass correlation coefficient (ICC) and 95% confidence interval (CI), Cronbach’ α, repeatability coefficient (RC), and coefficient of variation (CV) were used to evaluate the repeatability of Corvis ST parameters. Paired t test or Wilcoxon rank test was used to evaluate the differences between preoperative and postoperative data. RESULTS: At preoperative, 26 of 39 (66.67%) parameters showed good to excellent repeatability, 6 (15.38%) showed moderate, and 7 (17.95%) showed poor repeatability. Similarly, 34 (87.18%) parameters showed good to excellent repeatability, 3 (7.69%) showed moderate, and 2 (5.13%) showed poor repeatability after ATE-CXL. After ATE-CXL 1mo, the intraocular pressure (IOP), biomechanical corrected IOP (bIOP), first applanation time (A1T), Radius, deformation amplitude at the first applanation (A1DA), deflection length at the maximum deformation (HCDLL) and stiffness parameter at first applanation (SP A1) parameters increased, while the steep keratometry (Ks), flat keratometry (Kf), mean keratometry (Kmean), second applanation time (A2T), DA Ratio Max (2 mm) and integrated radius parameters decreased (all P<0.05). CONCLUSION: The repeatability of the Corvis ST parameters before and 1mo ATE-CXL follow up were both acceptable, and the corneal stiffness was improved after 1-month ATE-CXL.

Distribution of Corneal Geometric Landmarks and Relationship Between Their Distances and Biomechanical Parameters in the Development of Keratoconus.

Purpose: To analyze the changes in coordinates and distances among three typical geometric landmarks of the cornea, namely, the thinnest point (TP), maximum curvature (Kmax), and corneal apex (AP) during the development of keratoconus, and explore the potential relationship between these changes and the abnormalities of corneal biomechanics. Methods: Normal eyes (n = 127), clinical keratoconic eyes (CKC, n = 290), and the eyes of forme fruste keratoconus (FFKC, n = 85) were included; among them, the CKC group was classified into four grades based on the Topographic Keratoconus Classification (TKC) provided by Pentacam. A total of 38 Corvis ST output parameters and three distance parameters of three typical landmarks (DKmax-AP, DTP-AP, and DKmax-TP) based on Pentacam were included. The differences of parameters among the abovementioned six groups (Normal, FFKC, and CKC stage I to CKC stage IV) were analyzed. Spearman’s rank correlation test was performed to choose several dynamic corneal response (DCR) parameters that could best reflect the changes of corneal biomechanical characteristics during the progression of the disease, and the Pearson’s or Spearman’s correlation test was conducted to determine the association between the three distances and the selected DCR parameters in each grade. In addition, by flipping the X coordinate of the left eye on the vertical axis to reflect the direction of the right eye, the coordinates of TP and Kmax in different developmental grades were highlighted. Results: From CKC stage II, the three geometric landmark distances commenced to correlate with the corneal DCR parameters (CBI, SPA1, IR, DA Ratio 2, ARTh, MIR, Radius, Pachy, and DA Ratio 1), which could better represent the changes of biomechanical properties from normal cornea to keratoconus. From normal cornea to CKC stage IV, the coordinates of Kmax were gradually tended to the inferior temporal region from dispersion, while TP was always concentrated in the inferior temporal region. Although DKmax-AP, DKmax-TP, and DTP-AP all showed a gradual decreasing trend with the progress of the disease, the first two did not change significantly, and only DTP-AP significantly approached AP in the later stage of disease development. In addition, from the FFKC group, the corresponding values of DKmax-TP in each disease development group were smaller than DKmax-AP. Conclusions: In the later stage of keratoconus, the relationship between the three typical landmark distance parameters and DCR parameters is stronger, and even the weakening of corneal biomechanical properties may be accompanied by the merger of typical landmark positions.

Universal architecture of corneal segmental tomography biomarkers for artificial intelligence-driven diagnosis of early keratoconus

AimsTo develop a comprehensive three-dimensional analyses of segmental tomography (placido and optical coherence tomography) using artificial intelligence (AI).MethodsPreoperative imaging data (MS-39, CSO, Italy) of refractive surgery patients with stable outcomes...

Assessing the visual image quality provided by refractive corrections during keratoconus progression.

To expand the SyntEyes keratoconus (KTC) model to assess the Visual Image Quality (VIQ) of sphero-cylindrical spectacle and rigid contact lens corrections as keratoconus progresses. The previously published SyntEyes KTC eye model to determine best sphero-cylindrical spectacle and rigid contact lens correction in keratoconic eyes was expanded to include the natural progression of keratoconus, thus allowing the assessment of corrected VIQ with disease progression. As keratoconus progresses, the pattern of visual Strehl ratio (VSX) in correction space for spectacles alters from a typical hourglass into a shell pattern. The former would guide the subjective refraction towards the optimal correction while the latter is relatively insensitive to large dioptric steps. In 15 out of the 20 SyntEyes, the shell pattern eventually produces two foci on different sides of the correction space separated by a clinically significant dioptric difference with a similar, albeit lower VIQ. Wearing the best possible spectacle corrections provided an average gain of up to 3.5 lines of logMAR visual acuity compared to the uncorrected cases, which increased to 5.5 lines for the best rigid contact lens correction. Continuing to wear a spectacle correction as the disease progresses often leads to a VIQ that is almost as bad as the uncorrected case. Continuing to wear a rigid contact lens correction as the disease progresses maintains a relatively high level of VIQ, albeit in the low range for typically well-corrected normal eyes. The results reflect the clinical experience that subjective refraction is difficult in highly-aberrated keratoconic eyes, the benefit of spectacle correction is short lived and that rigid contact lenses provide better and more stable VIQ with disease progression. Other aspects, such as the presence and behaviour of the second focus in some cases, remain to be confirmed clinically.

The utility of measures of anterior segment parameters of a Pentacam Scheimpflug tomographer in discriminating high myopic astigmatism from keratoconus.

The study aimed to evaluate and compare anterior segment parameters between keratoconic eyes and eyes with high myopic astigmatism using Pentacam Scheimpflug tomography. This was a retrospective cross-sectional study that included sixty keratoconic eyes (thirty-two persons) and seventy-three eyes (forty-six persons) with high myopic astigmatism with mean ages 24.72 ± 11.65years and 26.60 ± 10.69years, respectively. Twenty-three parameters from the topographic map and fifteen parameters from the Belin-Ambrosió enhanced ectasia display map of the printouts of a Scheimpflug principle-based Pentacam tomographer were evaluated for their diagnostic accuracy using Receiver Operating Characteristic (ROC) curve. All parameters except cornea volume, anterior chamber volume, and anterior chamber angle indicated a significant difference between high myopic astigmatism and keratoconic eyes. The area under the receiver operating characteristic (AUROC) of eighteen Pentacam parameters was excellent (0.9-1.0) in discriminating keratoconus from high myopic astigmatism, out of which four {anterior minimum sagittal curvature (ant. Rmin), posterior minimum sagittal curvature (post. Rmin), maximum Ambrosió relational thickness (ART max) and total deviation value (D)} indicated excellent (>90%) sensitivity and specificity in addition to the excellent AUROC values. Topographic and Belin-Ambrosió enhanced ectasia display (BAD) maps of a Scheimpflug principle-based Pentacam tomographer are useful in enhancing the diagnosis of keratoconus and may also provide valuable information in effectively screening for keratoconus cases among refractive surgery candidates with high myopic astigmatism.

Performance of Zernike polynomials in reconstructing raw-elevation data captured by Pentacam HR, Medmont E300 and Eye Surface Profiler

PurposeTo investigate the capability of Zernike polynomials fitting to reconstruct corneal surfaces as measured by Pentacam HR tomographer, Medmont E300 Placido-disc and Eye Surface Profiler (ESP). MethodsThe study utilised a collection of clinical data of 527 participants. Pentacam HR raw elevation data of 660 eyes (430 healthy and 230 keratoconic) were fitted to Zernike polynomials of order 2 to 20. Same analyses were carried out on 158 eyes scanned by Medmont E300 Placido-disc and 236 eyes were scanned by ESP for comparison purposes. The Zernike polynomial ​fitting was carried out using a random 80% of each individual eye surface's data up to a corneal radius of 5 mm and the root means squared fitting error (RMS) was calculated for the unused 20% portion of the surface data. The process was carried out for the anterior and posterior surfaces of the corneal measurements of the Pentacam HR and the anterior surfaces only with the ESP and the Medmont E300 measurements. ResultsStatistical significances in reduction of RMS were noticed up to order 14 among healthy participants (p < 0.0001 for right eyes, p = 0.0051 for left eyes) and up to order 12 (p < 0.0001 for right eyes, p = 0.0002 for left eyes) in anterior surfaces measured by the Pentacam. Among keratoconic eyes, statical significance was noticed up to order 12 in both eyes (p < 0.0001 for right eyes, p = 0.0003 for left eyes). The Pentacam posterior corneal data, both right and left, healthy and keratotic eyes recorded significance (p < 0.0001) in reduction of RMS up to order 10 with same RMS values of 0.0003 mm with zero standard deviation. RMS of fitting Zernike polynomials to Medmont data up to order 20 showed a consistent reduction in RMS with the increase of the fitting order with no rise at high fitting orders. Minimum RMS = 0.0047 ± 0.0021 mm, 0.0046 ± 0.0019 mm for right and left eyes respectively were recorded at order 20 and were more than 15 times the minimum RMS of the Pentacam. RMS of fitting Zernike polynomials to ESP data also showed a consistent reduction in RMS with the increase of the fitting order with no sign of any rise at high fitting orders. Similar to the Medmont, minimum RMS of 0.0005 ± 0.0003 mm, 0.0006 ± 0.0003 mm was recorded at order 20 for right and left eyes respectively and was 2 times the minimum RMS of the Pentacam for right eyes and 1.7 times the minimum RMS of the Pentacam for left eyes. ConclusionsOrders 12 and 10 Zernike polynomials almost perfectly matched the raw-elevation data collected from Pentacam for anterior and posterior surfaces, respectively for either healthy or keratoconic corneas. The Zernike fitting could not perfectly match the data collected from Medmont E300 and ESP.

Evaluation of ocular biometric parameters in keratoconic eyes relative to healthy myopic eyes.

To assess the biometric features of keratoconic eyes using the Lenstar LS900 and Pentacam systems relative to healthy myopic eyes. Seventy-three eyes of keratoconic subjects and 83 eyes of control subjects were enrolled. To evaluate the reproducibility of the Lenstar and Pentacam devices' measurements, keratometric readings [in flattest meridian (Kf), in steepest meridian (Ks), and mean (Km)], central corneal thickness (CCT), and anterior chamber depth (ACD) were obtained using both systems. Axial length and lens thickness (LT) were measured by the Lenstar. The compatibility between the two devices was investigated using the Bland-Altman statistical method. Axial length was longer in the myopic group than in eyes with keratoconus (24.94 ± 0.7 and 23.88 ± 0.96 mm, respectively, p < 0.001). LT and vitreous depth were also higher in the myopic group, although ACD values were similar. Compared to the Lenstar, the Pentacam measured the ACD and CCT values higher in the myopia group [with a difference of 0.07 ± 0.12 mm (p <0.001) and 4.47 ± 11.33 µm (p = 0.001), respectively] and measured the CCT values higher in the keratoconus group. Pentacam found all keratometry values significantly lower than Lenstar in the keratoconus group. Axial length was longer in the myopic eyes due to the differences starting from the lens and extending to the posterior segment. Lenstar and Pentacam can be used interchangeably for Km, Kf, and ACD in the myopic group and only for ACD in the keratoconus group.

Pellucid marginal degeneration versus keratoconus: distinction with wide-field SD-OCT corneal sublayer pachymetry

PurposeTo evaluate the capability of wide-field spectral-domain optical coherence tomography (SD-OCT) corneal sublayer pachymetry to distinguish between keratoconus and pellucid marginal degeneration (PMD).MethodsThis prospective cross-sectional study included 69 eyes (59...

Contact Lens Fitting in Patients with Keratoconus - A Retrospective Assessment of 200 Patients.

Nowadays, keratoconus (KC) is very well treatable in a stage-oriented manner. A wide range of designs and materials of contact lenses (CL) are available for the treatment of KC. The aim of this study was to evaluate the possibilities, the possible challenges and the visual outcome of lens fitting in KC eyes. This retrospective study includes data from 200 patients who received a lens fitting trial in our contact lens service between 2006 and 2016. We documented ophthalmological parameters, the type of prescribed CL, the number of required trial lenses and possible causes of the failure of the lens fitting. The mean age at initial lens fitting was 33.9 ± 12.5 years. In 98.8% of the cases, the fitting was performed with rigid gas permeable lenses, in 90.1% with four-curve lenses. Of the total number of aspheric lenses prescribed, 87.5% were fitted in keratoconus stages "1" to "2" (topographic keratoconus classification; Oculus Keratograph). Back surface toric lenses or bitoric lenses were fitted to 61.7% in keratoconus stages "2 - 3" to "4". Before patients received their final CL, a median of 2 trial lenses were required (max. 16). Mean visual acuity with lens correction was 0.8 ± 0.2 at the initial fitting, mean visual acuity with glasses correction was 0.5 ± 0.3. In 7.7% of the eyes, the KC lens fitting was discontinued due to the advanced stage of keratoconus, requiring a corneal transplant. Reasons for discontinuing contact lens fitting included lens intolerance (2.3%), application problems (0.3%) or acute corneal hydrops (0.3%). Discontinuation of lens wearing due to incompatibilities or application problems occurred in only four cases (1.1%) in the further course after lens fitting. The use of contact lenses is an integral part of the stage-appropriate therapy of keratoconus. Good visual acuity can be achieved in all stages of keratoconus with a low drop-out rate. In most cases, the adjustment is carried out with rigid gas permeable lenses with a four-curve geometry. In initial stages, aspherical lenses may be sufficient. Toric lenses can be fitted in advanced stages when rotationally symmetrical lenses cannot achieve a satisfactory fit. If contact lenses have been successfully fitted, there are only a few cases in which patients abandon their contact lenses because of intolerance.

Toric intraocular lens power calculation in cataract patients with keratoconus.

Intraocular lens (IOL) power calculation in eyes with keratoconus typically results in hyperopic postoperative refractive error. The purpose of this study was to investigate the visual and refractive outcomes in patients with keratoconus having cataract surgery with a toric IOL and compare IOL power calculation accuracy of conventional formulas and keratoconus-specific formulas. Ein-Tal Eye Center, Tel-Aviv, Israel. Retrospective case-series study. Postoperative visual acuity and manifest refraction were examined. The error in predicted refraction and IOL power calculation accuracy within a range of 0.50 to 2.00 diopters (D) were compared between different IOL calculating formulas. 32 eyes with keratoconus were included. Visual acuity improved in all cases, and subjective astigmatism decreased from -2.95 ± 2.10 D to -0.95 ± 0.80 D (P < .001). The mean absolute errors were as follows: Barrett True-K formula for keratoconus with measured or predicted posterior corneal power, 0.34 D; Barrett Universal II formula, 0.64 D; Kane formula, 0.69 D; Kane formula for keratoconus, 0.49 D; SRK/T formula, 0.56 D; Haigis formula, 0.72 D; Holladay 1 formula, 0.71 D, and Hoffer Q formula, 0.87 D. Barrett True-K formula with measured posterior corneal power, SRK/T formula, and Kane formula for keratoconus resulted in a prediction error within ±0.50 D of 87.5%, 59.4%, and 53.1%, respectively. Cataract removal with a toric IOL significantly improves visual acuity and decreases astigmatism in keratoconic eyes with a topographic central relatively regular astigmatic component. Keratoconus-specific formulas resulted in lower mean error in predicted refraction compared with conventional calculating formulas. Using the posterior corneal power within the Barrett True-K formula for keratoconus improved IOL power prediction accuracy.

Keratoconus enlargement as a predictor of keratoconus progression

Numerous approaches have been designated to document progression in keratoconus, nevertheless there is no consistent or clear definition of ectasia progression. In this present study, we aim to evaluate Keratoconus Enlargement (KCE) as a parameter to document ectasia progression. We define KCE as an increase of more than 1D in the anterior curvature of non-apical corneal areas. We have designed a longitudinal study in 113 keratoconic eyes to assess keratoconus progression. KCE was compared with variables commonly used for detection of keratoconus progression like Kmax, Km, K2, PachyMin, D-Index, Corneal Astigmatism and PRC of 3.0 mm centered on the thinnest point. The variations of keratometric readings, D-index and ELEBmax showed positive associations with KCE. Evaluating the performance of Kmax, D-index and KCE as isolated parameters to document keratoconus progression we found a sensitivity of 49%, 82% and 77% and a specificity of 100%, 95% and 66% to detect keratoconus progression (p < 0.001 for all). This difference in sensitivity can be explained by the changes in keratoconus outside the small area represented by Kmax. The inclusion of KCE should be considered in the evaluation of keratoconus progression in conjunction with other variables to increase the reliability of our clinical evaluation.

Fluid reservoir thickness and aberration relationship in keratoconic eyes with scleral lenses.

To investigate the effect of varying the fluid reservoir (FR) thickness of scleral lenses (SL) on corrected distance visual acuity (CDVA), contrast sensitivity (CS) and higher-order aberrations (HOAs) in keratoconic eyes. Forty eyes with keratoconus were fitted with a diagnostic Boston Sight SL having three different FR thicknesses. CDVA, CS and HOAs were measured before and after 30min of lens wear. An i-Trace aberrometer and anterior segment optical coherence tomography (AS-OCT) were used to measure HOAs and FR thickness, respectively. Statistically significant improvements in CDVA and CS were seen with different FR thickness lenses (p<0.01). Baseline CDVA (0.22±0.15) improved to 0.03±0.06, 0.04±0.07 and 0.07±0.08 with low, standard and high FR lenses, respectively. Post-hoc testing showed better CDVA with low (p=0.006) and standard FR (p=0.009) lenses compared to high FR lenses. Before lens wear, CS was 1.27±0.27, which improved to 1.67±0.11, 1.73±0.12 and 1.66±0.89 with low, standard and high FR lenses, respectively. Lenses with standard FR showed better CS compared with those having low (p=0.009) and high FRs (p<0.001). A statistically significant reduction of higher order-root mean square aberrations (HO-RMS), coma, spherical aberration, secondary astigmatism and trefoil were found with all FR thickness lenses compared to baseline (p<0.01). No significant difference was noted between lenses (p=0.01). All three lenses corrected almost equal amount of HOAs. A moderate positive correlation was observed between CDVA and HO-RMS (r=0.61, p<0.001) for low FR lenses. BostonSight SCLERALs were found to be very effective in improving vision, CS and reducing HOAs in keratoconus. Lenses with varying FR thickness showed equal effectiveness in visual performance and reducing HOAs. FR thickness should be considered an important factor to provide better vision and CS by minimising HOAs, as well as to maintain the normal physiology of eyes with keratoconus.

Correlation between long-term use of rigid gas permeable contact lenses and endothelial morphometric changes in keratoconus patients

PurposeThis study was conducted to evaluate the effects of long-term use of rigid gas-permeable (RGP) contact lenses on corneal endothelium in keratoconus (KC) patients using non-contact specular microscopy. In addition, the correlation between wearing duration of RGP lenses (years & hours /d) and endothelial morphometric changes in KC patients was performed. This may provide more useful data for clinical application of RGP contact lens. Study designThis study was a prospective, observational, comparative, hospital based, nonrandomized, cross-sectional, and quantitative study. Subjects and methodsThe study included 40 eyes of non-wearer contact lens KC patients (group 1) and 38 KC eyes with a long history of Rose K2 RGP contact lens wearing (group 2). The corneal endothelial morphology such as endothelial cell density (ECD); coefficient of variation of cell area (CV); percentage of hexagonal cells (HEX); and central corneal thickness (CCT) were evaluated in all patients using SP3000P Specular Microscope. ResultsThe study included 40 eyes of non-wearer contact lens KC patients (20 mild KC eyes and 20 moderate KC eyes) and 38 KC eyes with a long history of RGP contact lens wearing (18 mild KC eyes and 20 moderate KC eyes). The mean duration of RGP lenses wearing was 5.67 ± 3.481 years & 12.11 ± 2.698 h/d in mild KC eyes and 7.15 ± 5.294 years &13.65 ± 2.889 h/d in moderate KC eyes. Wearing duration in hours in mild KC eyes showed a significant moderate negative correlation with ECD (r = −0.529, p = 0.024) and a moderate positive correlation with CV (r = 0.565, p = 0.015). In addition, wearing duration in years in moderate KC eyes showed a significant moderate negative correlation with ECD (r = −0.465, p = 0.039) and moderate positive correlation with CV (r = 0.627, p = 0.003). However, wearing duration in hours in moderate KC eyes showed a significant moderate negative correlation with HEX only (r = −0.490, p = 0.028). This study reported significant corneal thinning in contact lens wearer KC eyes in contrast to non-wearer KC eyes. ConclusionThis study documented a significant correlation between a long-term use of Rose K2 RGP using the three-point touch and corneal endothelial morphometric changes in KC patients. In addition, the current study confirmed a significant corneal thinning in RGP contact lens wearer compared to non-contact lens wearer KC patients. Further studies are recommended to evaluate the association between different RGP lens materials with different oxygen permeability transmissibility; different lens design types; different fitting methods; the duration of contact lens wear and the endothelial morphometric changes in KC patients.

Best Indicators for Detecting Keratoconus Progression in Children: A Report From the Shahroud Schoolchildren Eye Cohort Study.

The purpose of this study was to investigate 3-year changes in keratoconus (KC) indices to determine the indicators of KC progression compared with age-related changes in children aged 6 to 12 years. In this report of the Shahroud Schoolchildren Eye Cohort Study, KC was diagnosed based on vision, refraction, tomography, and slitlamp examination findings. KC progression was defined as changes in refractive astigmatism or zonal maximum keratometry (Zonal Kmax-3 mm). Then, 3-year changes (Δ) in vision, refraction, and tomographic indices were compared between progressive KC and normal eyes. The best set of ∆parameters for distinguishing KC progression from age-related changes were determined using the area under curve (AUC). Eighteen KC eyes and 10,422 normal eyes were analyzed. All KC cases showed progression after 3 years. Δindices were statistically different between the 2 groups except corrected distance visual acuity, anterior radius of curvature, irregularity index, and KC percentage index. The best Δindices, in descending order of AUC value, were index of height decentration, Zonal Kmax-3 mm, refractive astigmatism, single point Kmax, and index of vertical asymmetry (all AUC > 0.9), followed by inferior-superior asymmetry, index of surface variance, minimum corneal thickness, index of height asymmetry, KC index, posterior radius of curvature, and Belin/Ambrósio total Deviation (AUC = 0.8-0.9). According to our findings, changes in index of height decentration, Zonal Kmax-3 mm, refractive astigmatism, single point Kmax, and index of vertical asymmetry are the best indices for detecting KC progression in children younger than 12 years.

Repeatability of Corneal Deformation Response Parameters by Dynamic Ultra High-speed Scheimpflug Imaging in Normal and Keratoconus Eyes

To assess the repeatability of corneal dynamic response (CDR) parameters in normal and keratoconus (KC) eyes using ultra high-speed Scheimpflug imaging. Prospective, comparative, observational study, including eyes of 112 patients that underwent high-speed Scheimpflug imaging analysis (Corvis ST, OCULUS). Twenty-one CDR parameters were evaluated to asses repeatability using: coefficient of repeatability (CR), coefficient of variation, intraclass correlation coefficient (ICC) and within-subject SD. Three consecutive measurements by the same operator were performed for each eye. There were no significant differences between the three consecutive measurements for all parameters in both normal and KC eyes. 71.42% (15 of the 21 parameters evaluated) and 85.71% (18 of the 21 parameters) were highly repeatable in the normal and KC group, respectively. The tomographic biomechanical index (TBI), corneal biomechanical index (CBI), and stiffness parameter (SPA1) showed an ICC of 0.978, 0.954, and 0.958 in normal and 0.982, 0.892, and 0.978 in KC eyes, respectively. The CR in normal eyes for TBI, CBI, and SPA1 were 0.169, 0.242, and 14.12, respectively, and for KC eyes 0.06, 0.23, and 13.64, respectively. Most of the corneal dynamic response parameters were highly repeatable in normal and KC eyes.

Diagnosability of Keratoconus Using Deep Learning With Placido Disk-Based Corneal Topography.

Purpose: Placido disk-based corneal topography is still most commonly used in daily practice. This study was aimed to evaluate the diagnosability of keratoconus using deep learning of a color-coded map with Placido disk-based corneal topography.Methods: We retrospectively examined 179 keratoconic eyes [Grade 1 (54 eyes), 2 (52 eyes), 3 (23 eyes), and 4 (50 eyes), according to the Amsler-Krumeich classification], and 170 age-matched healthy eyes, with good quality images of corneal topography measured with a Placido disk corneal topographer (TMS-4TM, Tomey). Using deep learning of a color-coded map, we evaluated the diagnostic accuracy, sensitivity, and specificity, for keratoconus screening and staging tests, in these eyes.Results: Deep learning of color-coded maps exhibited an accuracy of 0.966 (sensitivity 0.988, specificity 0.944) in discriminating keratoconus from normal eyes. It also exhibited an accuracy of 0.785 (0.911 for Grade 1, 0.868 for Grade 2, 0.920 for Grade 3, and 0.905 for Grade 4) in classifying the stage. The area under the curve value was 0.997, 0.955, 0.899, 0.888, and 0.943 as Grade 0 (normal) to 4 grading tests, respectively.Conclusions: Deep learning using color-coded maps with conventional corneal topography effectively distinguishes between keratoconus and normal eyes and classifies the grade of the disease, indicating that this will become an aid for enhancing the diagnosis and staging ability of keratoconus in a clinical setting.

Axial Length and White to White Corneal Diameter in Eyes with Keratoconus

Abstract Objective To study the axial length (AL) and white to white (WTW) corneal diameter in keratoconus (KC) eyes and compare them to normal eyes. Methods Sixty-three eyes of 53 patients were included in this cross-sectional observational study divided into KC group comprised of 28 eyes of 18 patients and control group comprised of 35 eyes of 35 patients based on clinical and tomographic findings. All subjects were examined using rotating Scheimpflug corneal tomography (Pentacam HR; Oculyzer II) for central corneal thickness (CCT), thinnest corneal thickness (TCT), keratometric values, anterior chamber depth (ACD) and lens thickness, and by optical biometry (IOLMaster 500) for axial length (AL) measurements. Vitreous cavity length (VCL) was calculated by subtracting the values of CCT, ACD (internal), and lens thickness from the AL. White to white (WTW) corneal diameter was measured using Placido-based tomography (Topolyzer VARIO). Results The mean age was 31.27±8.65 years(30.39 ± 9.31) in the KC group and .(31.74 ± 8.38) in the non KC group. The KC group included 28 eyes their mean spherical equivalent (SE) was -3.16 ± 2.42 and the control group 35 healthy eyes including 23 ametropic eyes with mean spherical equivalent (SE) (-3.95±4.50 D) and 12 emmetropic eyes with mean SE (-0.19±0.40 D). The mean VCL was significantly greater in normal eyes (17.45 ±1.34 mm) compared with KC (16.77±1.18 mm) (P = 0.037), while the mean ACD (internal) was significantly greater in KC eyes compared to normal (P = 0.020) and the lens thickness showed no statistically significant difference. The greater VCL in the normal group was compensated by the greater ACD in the KC group causing the total AL to have no statistically significant difference (normal eyes =24.44 ±1.38 mm and KC eyes= 24.21 ±1.31 mm) (P = 0.513). There was no statistically significant difference in the WTW corneal diameter between KC and normal eyes (11.81 ±0.35 mm in the normal group compared to 11.79 ±0.35 mm in the KC group) (P = 0.835). Conclusion VCL was significantly greater in normal eyes compared with those eyes with KC. AL and WTW showed no difference between the two groups.

Anterior segment-optical coherence tomography for evaluation of the epithelium thickness profile in keratoconic corneas and normal corneas

Purpose This study intends to compare the characteristic distributive epithelial pattern by Fourier-domain anterior segment-optical coherence tomography (AS-OCT) corneal mapping between keratoconic and normal eyes. Patients and methods This prospective case–control study included 51 participants who were divided into two groups: study group A (formed of 50 eyes of 26 keratoconic participants) and control group B (50 eyes of 25 healthy controls of matched age and sex with group A). Maps of corneal epithelial statistics within central 5 mm [S: 2–5 mm (superior), I: 2–5 mm (inferior), minimum, maximum, SD (topographic variability), minimum−maximum], and the total corneal pachymetry maps were assessed by the Fourier-domain AS-OCT system and imaged by Scheimpflug imaging corneal topography for both groups. Results For group A of keratoconic corneas, the attained results are as follows: the mean of epithelial thickness at the center was 50.1±7.98 µm, superior 56.01±6.98 µm, inferior 48.73±5.97 µm, minimum 39.95±9.11 µm, maximum 62.92±8.85 µm, minimum−maximum −22.01±10.91 µm, and topographic variability 6.9±4.2 µm. For group B of healthy control eyes, the mean of epithelial thickness at the center was 52.71±3.71 µm, superior 52.29±3.32 µm, inferior 53.42±3.11 µm, minimum 48.89±3.71 µm, maximum 55.92±3.47 µm, minimum−maximum −6.3±3.51 µm, and topographic variability 1.53±0.82 µm. All variables of epithelial thickness between the two groups are significant (P&lt;0.01). In comparing the epithelial map of keratoconus (KCN) with the control group, the epithelium was found to be thicker at the maximum (+7 µm) and superior location (+3.72 µm), but thinner at the minimum (−8.94 µm) and the inferior (−4.69 µm) with highly significant differences in both minimum−maximum (−15.71) and topographic variability (+5.37). Moreover, in KCN, the point of minimum epithelial thickness was in accordance with the minimum point of the total corneal thickness and the maximum point of back elevation. Conclusion The mapping for epithelial thickness utilizing AS-OCT could be a promising tool in KCN diagnosis.

Validation and Repeatability of Inferior minus Superior Value and its Cut-off Value in Anterior Sagittal Curvature Map Using Pentacam in Early Keratoconus

Abstract Background : Keratoconus (KC) is a bilateral asymmetric localised inferior and central corneal thinning and ectasia. Usually, it causes high myopia and irregular astigmatism resulting in a poor quality of vision. One of the most important ways of avoiding iatrogenic ectasia in cornea during refractive surgery is to detect KC in its earliest stage using the Pentacam. An important asymmetry decentration index is the inferior minus superior (IS) value. Purpose : Detection of Inferior minus Superior (IS) value and its Cut-off Value Methods : This is a cross-sectional, case control study that included 92 right eyes of 92 subjects, who presented to the outpatient clinic of “Al Watany Eye Hospitals” seeking refractive surgery or routine medical consultations. Our study focused on the measurement of the IS-value in early KC (TKC grade 1 and FFKC) and normal eyes. The right eye of each candidate was scanned 5 times in the same setting using the Pentacam. The study adhered to the tenets of the Declaration of Helsinki, and an approval was obtained from the ethical committee of Ain Shams University Hospitals. Results : We detected remarkably high statistically significant difference between patients and controls regarding the IS-value (p &amp;lt; 0.001). The mean (±SD) of control and cases group was 0.3 ± 0.2 and 1.4 ± 0.6, respectively. The cut-off point of 0.69 with high area under the receiver operating characteristic (AUROC). Coefficient of variation median (95% CI) for cases and controls were 1.4% (0.9 to 3.1%) and 6.2% (3 to 9.4%), respectively. Conclusion : The IS-value has a high repeatability and AUROC for differentiating early KC from normal corneas. It can be regarded as an accurate parameter for early KC detection.