Early Diagnosis Of Keratoconus Research Articles

Corneal biomechanics in early diagnosis of keratoconus using artificial intelligence.

Keratoconus is a blinding eye disease that affects activities of daily living; therefore, early diagnosis is crucial. Great efforts have been made toward an early diagnosis of keratoconus. Recent studies have shown that corneal biomechanics is associated with the occurrence and progression of keratoconus. Hence, detecting changes in corneal biomechanics may provide a novel strategy for early diagnosis. However, an early keratoconus diagnosis remains challenging due to the subtle and localized nature of its lesions. Artificial intelligence has been used to help address this problem. Herein, we reviewed the literature regarding three aspects of keratoconus (keratoconus, early keratoconus, and keratoconus grading) based on corneal biomechanical properties using artificial intelligence. Furthermore, we summarized the current research progress, limitations, and possible prospects.

Early Diagnosis of Keratoconus and Morphological Analysis of Corneas with Physiologically Lower Central Thickness

Early Diagnosis of Keratoconus and Morphological Analysis of Corneas with Physiologically Lower Central Thickness

Visual improvement after corneal collagen cross-linking in keratoconus

This study was carried out to evaluate the effect of corneal collagen cross-linking on visual acuity, astigmatism and topographic readings (K1, K2, Kapex). : A nonrandomized noncontrolled clinical study was conducted in two tertiary eye centres in Bangladesh from July 2017 to June 2019. All attending patients diagnosed with Keratoconus were included in this study according to selection criteria. Patients with a corneal thickness of fewer than 400 microns, previous viral infection, cornea scarring, corneal opacification, severe ocular surface disease, history of immune disorders, pregnancy, and breastfeeding were excluded from the study. All selected patients underwent collagen cross-linking with Riboflavin and Ultraviolet A, followed up five days, one and six months following the procedure. Visual acuity, topographic readings (K1, K2, Kapex) and cylindrical values were assessed on every visit. The mean value of visual acuity was compared statistically with the baseline value.: A total of 30 eyes of 30 patients were studied in this study. The male-to-female ratio was 2:1. The Mean age (± SD) of the study subjects was 22.7±7.10. Before CXL, the Mean uncorrected visual acuity (UCVA) ±SD was 0.86±.35. In post-CXL follow-up time, the mean UCVA±SD was 0.46±.23 after six months of CXL. Before CXL, the Mean BCVA±SD was 0.35±.22. In post CXL era, the Mean ± SD BCVA was 0.14±.13 after six months of CXL. The Mean K1±SD was 45.66±3.43 before CXL, and the result changed after CXL. The Mean K1±SD was 43.29±3.29 after six months of CXL. The Mean K2±SD was 50.22±5.93 before CXL, and the result differed after six months of CXL. The Mean Kapex ±SD was 54.50±7.38 before CXL, and that was 51.32±6.93 after six months of CXL. Keratoconus is a bilateral non-inflammatory disorder progressively leading to vision-threatening ocular morbidity. Collagen cross-linking improves visual and topographic findings– K1, K2, and Kapex and reduces astigmatism. Early diagnosis of Keratoconus and prompt treatment will help achieve better vision.

Effect of hormones on keratoconus and its mechanism

Keratoconus is an ectatic corneal disorder and characterized by central and/or inferior temporal corneal thinning in a cone shape. Studies have shown that its pathogenesis is related to changes in tissue proteins, enzymes, immune functions and specific genes, but the exact pathogenesis has not been clearly clarified yet. Hormones such as sex hormones have been found to be associated with keratoconus. This review aims to summarize and analyze the research progress of the effect of hormones on keratoconus and its mechanism, so as to explore the role of hormones in the early diagnosis of keratoconus and find new targets in the treatment of keratoconus, providing reference for clinical work.

Characteristics of pediatric keratoconus and the role of corneal topography in early diagnosis: A prospective study

Purpose: The purpose of this study is to describe the clinical and topographical features of keratoconus in children and to emphasize the role of corneal topography in early diagnosis of keratoconus in eyes with astigmatism. Materials and Methods: It was a prospective study done to screen children below 18 years with astigmatism of 1.50 Diopter or greater for presence of keratoconus. Ophthalmic evaluation included retinoscopy, cycloplegic refraction, and detailed slit lamp examination for clinical diagnosis of keratoconus. All eyes underwent corneal topography and tomography. Eyes were followed up for progression with both refraction and corneal topographic imaging. Progressive cases later underwent Accelerated Collagen Crosslinking (ACXL). Results: 700 eyes of 350 patients with astigmatism were screened for keratoconus. 44 eyes of 28 patients were diagnosed with keratoconus. Mean age of the diagnosed children was 11.7 years (6–18 years), 18 boys and 10 girls. Overall, most common clinical association was allergic conjunctivitis. Twenty-five eyes (57%) had clinical evidence of keratoconus while other 19 eyes (43%) required corneal topography to establish the diagnosis. Based on the Amsler-Muckenheim tomographical classification, 22 of 44 eyes (50%) were grouped in prestage level followed by 13 eyes (29.5%) in Stage 1, 5 eyes (11.4%) in Stage 2, and 4 eyes (9.1%) in Stage 3. Thirty-five eyes of 21 patients showed progression and underwent ACXL. Conclusion: Early detection of keratoconus in children with astigmatism is of utmost importance to avoid visual impairment and surgical intervention. Even in the absence of clinical signs, corneal topography and tomography should be performed as a screening tool to rule out keratoconus in these children.

Análise comparativa entre os índices tomográficos em pacientes com ceratocone inicial

Objective: To assess sensitivity of corneal volume, corneal asphericity, and D index in early diagnosis of keratoconus. Methods: A cross-sectional analytical study, carried out between December 2018 and October 2020, which analyzed the medical records of 39 patients (78 eyes) diagnosed as keratoconus by a single corneal specialist, using the criteria of Belin-Ambrosio Enhanced Ectasia Display. The collected data were anterior asphericity, posterior asphericity, D index and its parameters (Da, Db, Dt, Dp and Df). The data were entered [...]

Sequence of events leading to diagnosis of keratoconus and its impact on quality of life

Purpose:Early diagnosis of keratoconus (KCN) and corneal collagen cross-linking can ensure that best-corrected visual acuity is preserved. We report the sequence of events leading to the diagnosis of KCN, as well as its impact on quality of life.Methods:This survey-based study included patients diagnosed with KCN for the first time at our center. Their corneal tomography was analyzed, and they were provided with a proforma and the NEI-VFQ-25 questionnaire and were asked to answer the given set of questions.Results:The study included 328 eyes of 164 patients. At the time of diagnosis, 112 (68.3%) patients were not aware of a disease called “keratoconus.” VKC was present in 56 patients, and 92 patients were not aware of the need to avoid eye rubbing. In total, 101 patients gave a history of sleeping more often on the side with worse KCN. The preferred primary point of contact was an optometrist for 45.1% of patients; 51.2% of patients reported never having visited an ophthalmologist. Sixty-four (39%) patients were advised a screening test to rule out KCN before presenting to our center; 42 (71.8%) of these patients did not get it done. Vision-targeted score showed a significant negative correlation with grade of KCN (r value: −0.471) and positive correlation (r value: 0.534) with LogMAR vision.Conclusion:KCN is a disease of the young and severely affects the quality of life. Improving awareness of the general public, ensuring timely referral by optometrists, and keeping a high index of suspicion is emphasized.

Biomechanics of the keratoconic cornea: Theory, segmentation, pressure distribution, and coupled FE-optimization algorithm

Understanding of the corneal biomechanical properties is of high interest due to its potential application in the early diagnosis of keratoconus (KC). KC by itself is a non-inflammatory eye disorder causes corneal structural and/or compositional anomalies. The biomechanically weakened cornea is no longer able to preserve the normal shape of the cornea against the intraocular pressure (IOP) and gradually starts to bulge outward, invoking a conical shape and subsequent distorted vision. The most popular way to measure the in vivo corneal biomechanical properties is the CorVis-ST, which enables to analyze the dynamic response of the cornea under a temporary air puff pressure. However, the complications, such as the lack of knowledge on the accurate air-puff pressure distribution on the cornea’s surface as a function of the distance from the apex of the cornea as well as the time, hinder us to have a reliable estimation of the cornea’s mechanical parameters. This study aims to establish patient-specific geometries of the healthy and KC corneas and calculate the pressure distribution on the cornea’s surface as a function of both the distance from the apex of the cornea and time, and thereafter, the viscoelastic mechanical properties of both the healthy and KC corneas using a coupled finite element (FE)-optimization algorithm. To do that, the dynamic deformation response of six healthy and six KC corneas were measured via CorVis-ST. The videos of the in vivo deformation of the corneas under the applied air puff pressure were segmented using our segmentation algorithm to determine the anterior and posterior curvatures of the corneas during the dynamic movement of the cornea. The FE model of the corneas were established using the segmented data and subjected to a negative (pre-stress), positive IOP, and air puff pressure while the floating boundary conditions were applied to the two ends of the corneas’ FE models. The simulation results were imported into a loop of FE-optimization algorithm and analyzed until the deformation amplitude at the apex of the cornea reaches to its minimum difference compared to the clinical data by CorVis-ST. The results revealed that the pressure distributions found in the literature as a function of the distance from the apex of the cornea and time unable to provide satisfactory results. Therefore, the pressure distributions both as a function of the distance and time were optimized using our coupled FE-optimization algorithm and employed to estimate the viscoelastic properties of the healthy and KC corneas. The mean percentage error (MPE) of 8.45% and 10.79% were found for the healthy and KC corneas compared to the clinical data of CorVis-ST, respectively. The results also revealed a significantly higher short-time shear modulus for the KC (62.33 MPa) compared to the healthy (37.45 MPa) corneas while the long-time shear modulus of both the healthy and KC corneas were almost the same (4.01 vs. 3.91 MPa). The proposed algorithm is a noninvasive technique capable of accurately estimating the viscoelastic mechanical properties of the cornea, which can contribute to understand the mechanism of KC development and improve diagnosis and intervention in KC.

A review of imaging modalities for detecting early keratoconus.

Early identification of keratoconus is imperative for preventing iatrogenic corneal ectasia and allowing for early corneal collagen cross-linking treatments to potentially halt progression and decrease transplant burden. However, early diagnosis of keratoconus is currently a diagnostic challenge as there is no uniform screening criteria. We performed a review of the current literature to assess imaging modalities that can be used to help identify subclinical keratoconus. A Pubmed database search was conducted. We included primary and empirical studies for evaluating different modalities of screening for subclinical keratoconus. A combination of multiple imaging tools, including corneal topography, tomography, Scheimpflug imaging, anterior segment optical coherence tomography, and in vivo confocal microscopy will allow for enhanced determination of subclinical keratoconus. In patients who are diagnostically borderline using a single screening criteria, use of additional imaging techniques can assist in diagnosis. Modalities that show promise but need further research include polarization-sensitive optical coherence tomography, Brillouin microscopy, and atomic force microscopy. Recognition of early keratoconus can reduce risk of post-refractive ectasia and reduce transplantation burden. Though there are no current uniform screening criterion, multiple imaging modalities have shown promise in assisting with the early detection of keratoconus.

A predictive model for early diagnosis of keratoconus

BackgroundThe diagnosis of keratoconus in the early stages of the disease is necessary to initiate an early treatment of keratoconus. Furthermore, to avoid possible refractive surgery that could produce ectasias. This study aims to describe the topographic, pachymetric and aberrometry characteristics in patients with keratoconus, subclinical keratoconus and normal corneas. Additionally to propose a diagnostic model of subclinical keratoconus based in binary logistic regression models.MethodsThe design was a cross-sectional study. It included 205 eyes from 205 patients distributed in 82 normal corneas, 40 early-stage keratoconus and 83 established keratoconus. The rotary Scheimpflug camera (Pentacam® type) analyzed the topographic, pachymetric and aberrometry variables. It performed a descriptive and bivariate analysis of the recorded data. A diagnostic and predictive model of early-stage keratoconus was calculated with the statistically significant variables.ResultsStatistically significant differences were observed when comparing normal corneas with early-stage keratoconus/ in variables of the vertical asymmetry to 90° and the central corneal thickness. The binary logistic regression model included the minimal corneal thickness, the anterior coma to 90° and posterior coma to 90°. The model properly diagnosed 92% of cases with a sensitivity of 97.59%, specificity 98.78%, accuracy 98.18% and precision 98.78%.ConclusionsThe differential diagnosis between normal cases and subclinical keratoconus depends on the mínimum corneal thickness, the anterior coma to 90° and the posterior coma to 90°.

Assessment of corneal viscoelasticity using elastic wave optical coherence elastography.

The corneal viscoelasticity have great clinical significance, such as the early diagnosis of keratoconus. In this work, an analysis method which utilized the elastic wave velocity, frequency and energy attenuation to assess the corneal viscoelasticity is presented. Using phase-resolved optical coherence tomography, the spatial-temporal displacement map is derived. The phase velocity dispersion curve and center frequency are obtained by transforming the displacement map into the wavenumber-frequency domain through the 2D fast Fourier transform (FFT). The shear modulus is calculated through Rayleigh wave equation using the phase velocity in the high frequency. The normalized energy distribution is plotted by transforming the displacement map into the spatial-frequency domain through the 1D FFT. The energy attenuation coefficient is derived by exponential fitting to calculate the viscous modulus. Different concentrations of tissue-mimicking phantoms and porcine corneas are imaged to validate this method, which demonstrates that the method has the capability to assess the corneal viscoelasticity.

Early Diagnosis of Keratoconus in Chinese Myopic Eyes by Combining Corvis ST with Pentacam

ABSTRACTPurpose: This study was designed to evaluate and compare the sensitivity and specificity of the Belin/Ambrósio Deviation (BADD), Corneal Biomechanical Index (CBI) and Tomographic and Biomechanical Index (TBI) for the diagnosis of keratoconus in Chinese myopic eyes prior to undergoing corneal refractive surgery.Methods: A total of 125 patients (185 eyes) planned to undergo corneal refractive surgery were selected from the Refractive Center of Beijing Tongren Hospital between December 2017 and December 2018. They were divided into four groups: the normal group, bilateral keratoconus (BK) group, unilateral keratoconus (UK) group, and the forme fruste keratoconus (FFK) group. After determining the BADD, CBI, and TBI for each eye using the Corvis ST combined with Pentacam, the sensitivity and specificity of these three indices in diagnosing keratoconus were analyzed through receiver operating characteristic (ROC) curves.Results: The TBI exhibited the highest diagnostic efficiency in normal vs. UK (area under the ROC curve [AUROC]: 0.992), normal vs. UK+BK (AUROC: 0.988), normal vs. UK+BK* (*stand randomly selecting one eye of each patient in BK group) (AUROC: 0.982), normal vs. UK+BK+FFK (AUROC: 0.965), and normal vs. UK+BK*+FFK (AUROC: 0.953). The CBI demonstrated the highest diagnostic efficiency in normal vs. FFK (AUROC: 0.897). Finally, the BADD showed the highest diagnostic efficiency in normal vs. BK (AUROC: 0.998) and normal vs. BK* (AUROC: 0.996).Conclusion: The BADD, CBI, and TBI performed well in diagnosing keratoconus in Chinese myopic eyes. The CBI showed the highest diagnostic efficiency compared with normal for FFK. In addition, the TBI offered the greatest accuracy in detecting keratoconus and FFK eyes vs. the other parameters.

Role of Anterior Segment Optical Coherence Tomography in The Diagnosis of Subclinical Keratoconus in Comparison with The Pentacam

Background: The most common ectatic disorder is keratoconus which is characterized by bilateral and progressive corneal thinning. Role of the pentacam has been well established for screening form fruste keratoconus in ophthalmology practice. While for anterior segment OCT it can detect the characteristic abnormal corneal thinning in patients with keratoconus using its pachymetry maps. Aim of the Work: was to detect how much anterior segment OCT can approach the pentacam’s well established efficacy in diagnosis of early keratoconus among the highly myopic astigmatic patients. Patients and Methods: This prospective, non-randomized population study followed the tenets of the Declaration of Helsinki, and the protocol was reviewed and approved by the Ophthalmology Department of Ain Shams University. An informed consent was signed by the patients before inclusion. We selected 40 eyes of twenty-three healthy young volunteers with high myopic astigmatism for the study from patients who attended the outpatient clinic of Maghraby Eye Hospital at the period of November and December 2017. Results: This study included 40 eyes of healthy young adults (22 females, 18 males) with high myopic astigmatism (-4.038 D± 1.194). The mean age ± SD was 24.1 ± 5.702 (range: 16-31 years). Statistically highly significant differences were observed in all measured cases between Pentacam and Anterior Segment OCT (p <0.01). So the OCT corneal pachymetry mapping seems promising for evaluating corneas as in cases of early keratoconus. Conclusion: The OCT corneal pachymetry mapping with its fast acquisition time seems promising for evaluating highly astigmatic corneas, as in early keratoconus.

Wavefront analysis: An additional tool for detection of keratoconus

Aims: The aim of this study is to analyze the role of wavefront analysis as an additional tool for the detection of keratoconus in three groups of patients (i.e., simple refractive errors, high astigmatism, and keratoconus). Design: This study was a prospective comparative study. Patients and Methods: In this prospective comparative study, a total of 115 eyes of 62 patients were examined. All the patients had a complete examination done, which included best spectacle-corrected visual acuity, slit-lamp and fundus examination, and corneal topography for diagnosis of keratoconus. Higher-order aberrations (HOAs) (coma, spherical aberration, and trefoil) were examined using Tscherning aberrometer, based on WaveLight® analyzer II. Statistical Analysis: The one-way analysis of variance test was used. Results: Spherical aberrations were reported highest in the patients with high astigmatism (mean value: 0.149), which was statistically significant when compared to simple refractive errors (P = 0.046). Trefoil aberrations were reported highest in patients with high astigmatism group (mean value: 5.579) in comparison to the other two groups (i.e., simple refractive errors and keratoconus) but were not statistically significant (P > 0.05). Coma and total aberrations were reported highest in keratoconus group (mean value: 0.314 and 2.058, respectively) in comparison to other groups (i.e., simple refractive error and high astigmatism), which was found to be highly significant (P = 0.000). Root-mean-square values of Zernike coefficient polynomials up to the third order were analyzed. Conclusions: This study highlights that assessment of HOAs using wavefront analysis can be used as an additional tool in the early diagnosis of keratoconus in addition to other standard methods.

Biomechanical properties of early keratoconus: Suppressed deformation signal wave.

To examine the diagnostic validity of different corneal biomechanical parameters for the detection of early keratoconus METHODS: Sixty-one eyes with a diagnosis of early keratoconus and 61 topographically normal eyes were enrolled in the study. All participants underwent testing with the Ocular Response Analyzer (ORA), and 40 indices from each cornea were included in the analysis. The mean (standard deviation: SD) of keratometry and central corneal thickness in keratoconic corneas was 46.9 (2.5) diopter (D) and 473 (31) μm, respectively. Of the 40 evaluated indices, 32 showed a significant difference between the two groups using t-test (p<0.05). According to the results of logistic regression, the indices of height from the lowest to the highest point in peak 2 (H21) and corneal resistance factor (CRF) with R2=0.79 were the best predictors of early keratoconus (p<0.001). H21 ≤190 with a sensitivity and specificity of 87% and 91.8%, respectively, and CRF≤8.6 with sensitivity and specificity of 87% and 85.3%, respectively, yielded an overall diagnostic accuracy of 97.3%. This study results point to the important role of novel waveform-derived indices measured by ORA, along with conventional biomechanical indices, for the early diagnosis of keratoconus. The best predictors of keratoconus in its early stages are H21 and CRF which showed very high sensitivity and specificity for the detection of early keratoconus.

Epithelial, Stromal, and Total Corneal Thickness in Keratoconus: Three-dimensional Display With Artemis Very-high Frequency Digital Ultrasound

To characterize the epithelial, stromal, and total corneal thickness profile in a population of eyes with keratoconus. Epithelial, stromal, and total corneal thickness profiles were measured in vivo by Artemis very high-frequency (VHF) digital ultrasound scanning (ArcScan) across the central 6- to 10-mm diameter of the cornea on 54 keratoconic eyes. Maps of the average, standard deviation, minimum, maximum, and range of epithelial, stromal, and total corneal thickness were plotted. The average location of the thinnest epithelium, stroma, and total cornea were found. The cross-sectional semi-meridional stromal and total corneal thickness profiles were calculated using annular averaging. The absolute stromal and total corneal thickness progressions relative to the thinnest point were calculated using annular averaging as well as for 8 semi-meridians individually. The mean corneal vertex epithelial, stromal, and total corneal thicknesses were 45.7+/-5.9 microm, 426.4+/-38.5 microm, and 472.2+/-41.4 microm, respectively. The average epithelial thickness profile showed an epithelial doughnut pattern characterized by localized central thinning surrounded by an annulus of thick epithelium. The thinnest epithelium, stroma, and total cornea were displaced on average by 0.48+/-0.66 mm temporally and 0.32+/-0.67 mm inferiorly, 0.31+/-0.45 mm temporally and 0.54+/-0.37 mm inferiorly, and 0.31+/-0.43 mm temporally and 0.50+/-0.35 mm inferiorly, respectively, with reference to the corneal vertex. The increase in semi-meridional absolute stromal and total corneal thickness progressions was greatest inferiorly and lowest temporally. Three-dimensional thickness mapping of the epithelial, stromal, and total corneal thickness profiles characterized thickness changes associated with keratoconus and may help in early diagnosis of keratoconus.